Who volunteers and why? Understanding the role of resources and motivations in
participation in voluntary work
Niebuur, Jacobien
DOI:
10.33612/diss.133869314
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Publication date:
2020
Link to publication in University of Groningen/UMCG research database
Citation for published version (APA):
Niebuur, J. (2020). Who volunteers and why? Understanding the role of resources and motivations in
participation in voluntary work. University of Groningen. https://doi.org/10.33612/diss.133869314
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work: a systematic review and
meta-analysis of longitudinal cohort studies
Jacobien Niebuur
Lidy van Lente
Aart. C. Liefbroer
Nardi Steverink
Nynke Smidt
BMC Public Health (2018) 18:12132
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ABSTRACT
Background: Participation in voluntary work may be associated with individual and societal benefits. Because of these benefits and as a result of challenges faced by governments related to population ageing, voluntary work becomes more important for society, and policy measures are aimed at increasing participation rates. In order to effectively identify potential volunteers, insight in the determinants of volunteering is needed. Therefore, we conducted a systematic review including meta-analyses. Methods: A systematic search in MEDLINE, PsycINFO, SocINDEX, Business Source Premier, and EconLit was performed on August 12th 2015. We included longitudinal cohort studies conducted in developed countries that quantified factors associated with volunteering among samples from the general adult population. Two reviewers independently selected eligible studies, extracted the data and assessed the risk of bias of the included studies using the QUIPS tool. Estimates reported in the papers were transformed into Odds Ratios and 95% Confidence Intervals. For each determinant, random-effects meta-analyses were used to generate summary estimates.
Results: We found that socioeconomic status, being married, social network size, church attendance and previous volunteer experiences are positively associated with volunteering. Age, functional limitations and transitions into parenthood were found to be inversely related to volunteering.
Conclusions: Important key factors have been identified as well as gaps in the current literature. Future research should be directed towards deepening the knowledge on the associations between the factors age, education, income, employment and participation in voluntary work. Moreover, major life course transitions should be studied in relation to volunteering.
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BACKGROUND
Participation in voluntary work can have several individual and societal benefits. It is inversely related to mortality1,2, depression2,3 and functional limitations3, and
positively related to self-rated health3. In turn, improved individual health is reflected
in more societal sustainability, for example in terms of health care systems4.
Furthermore, societal benefits of volunteering include increases in social solidarity and individuals’ involvement in society5 as well as economic benefits, for example
in terms of contributions to Gross Domestic Product levels6. Because of the various
socioeconomic benefits of volunteering and because of the current challenges faced by many developed countries related to population ageing, many policy measures are aimed nowadays at increasing participation rates in volunteering. In order to effectively target potential volunteers and to utilize the benefits related to volunteering, there is a need to understand the key factors related to participation in voluntary work. One important set of key factors are socio-demographic characteristics. By socio-demographic characteristics we mean characteristics that signify an individual’s position in society. This includes indicators of an individual’s position in the family domain (such as partner status and social network integration), the economic domain (such as education and income) and in the health domain (such as wellbeing). All these socio-demographic characteristics are examples of factors for which an association with volunteering is expected. Our research questions are: 1. What are the determinants (e.g. socio-demographic characteristics) of participation
in voluntary work?
2. What is the magnitude and direction of the relationship between identified determinants (e.g. socio-demographic characteristics) and participation in voluntary work?
Voluntary work is defined as “unpaid non-compulsory work; that is, time individuals give without pay to activities performed either through an organization or directly for others outside their own household”5. Research on factors influencing participation in
voluntary work is extensive. However, there is large heterogeneity in the determinants measured as well as in the findings. Inconsistencies in findings may result from, among other factors, the use of incomparable study samples, the use of different study designs and the omission of important confounders in analyses. By conducting a systematic review and meta-analysis, sources of heterogeneity in the findings can
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be further explored and reliable key factors influencing participation in voluntary work can be identified.
Although, earlier systematic reviews on determinants of participation in voluntary work provide important contributions to the knowledge on factors related to volunteering, most of them focussed on study samples consisting exclusively of volunteers recruited at voluntary organizations7,8, older people7, or volunteers
working for a specific cause (i.e. volunteering in the care of people with mental illnesses)8. Moreover, both reviews included studies using diverse study designs
(both quantitative as well as qualitative), and findings were not quantified7,8. Wilson9
provided an overview of theories explaining volunteerism and described several well-known determinants of volunteering, including level of education (positive association), age (curvilinear relationship), gender (in North-America, women are more likely to volunteer than men), marital status (married people are more likely to volunteer than non-married people) and health status (positive relationship). As the overview is based on literature published up until the year 2000, the findings did not result from conducting a review following a systematic approach, and associations were not quantified by conducting meta-analyses, there is need for updating the knowledge on the determinants of participation in voluntary work. Our aim was to improve the current knowledge by conducting a systematic review including a meta-analysis. Thereby, we aimed at summarizing the available evidence on the determinants of participation in voluntary work and determining the magnitude and direction of the relationship between identified determinants and participation in voluntary work.
METHODS
This systematic review was conducted according to the methods of the Cochrane Collaboration10 and reported according to the PRISMA (Preferred Reporting Items for
Systematic Reviews and Meta-Analyses) guidelines11.
Search strategy and study selection
A search was conducted in MEDLINE, PsychINFO, SocINDEX, Business Source Premier and EconLit, on August 12th, 2015. The search strategy included a combination
of terms related to (a) participation in voluntary work (e.g. voluntary work, volunteers, unpaid work) and (b) determinants (e.g. determinant, factor, association, relation, reason) (see Appendix 1).
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Articles were selected if they are (a) peer-reviewed full text publications reporting an association between at least one individual factor (contextual factors are beyond the scope of this study) and participation in formal voluntary work (i.e. voluntary work carried out for organizations12) (yes/no) in a quantitative way using a longitudinalprospective cohort study design (i.e. studies in which the determinant is measurement at a moment in time before the outcome was measured), and (b) making use of a study sample consisting of adults aged 18 and over from a general population from a developed country (i.e. Japan and countries in Europe, North America and Oceania). Moreover, (c) the article has to be published in English, French, German or Dutch within the time period 2010 – 2015. Given the large number of publications on the topic, we decided to focus on recent publications from 2010 onwards. Articles exclusively including informal volunteering as the outcome were excluded. In case it is unclear whether volunteering was formal or informal, articles were included and labelled as ‘mixed type of voluntary work’. Finally, articles focusing on very specific cases of volunteering such as disaster volunteering, corporate volunteering and volunteer-tourism were excluded as well, because of their limited comparability with volunteering in the general population, but also because the motives to participate in these kinds of voluntary work may differ from situation to situation. We focus on longitudinal rather than on cross-sectional studies, as the former offer better opportunities for temporal ordering of factors.
The titles and abstracts of all identified records were screened for eligibility by two reviewers (J.N. and L.v.L.) independently. Subsequently, the same two reviewers independently screened the full-text of all potentially eligible articles. Finally, all references of included articles were screened by one reviewer (J.N.) for potentially eligible articles.
Data extraction and assessment of risk of bias
Two reviewers (J.N. and L.v.L.) independently extracted the data regarding the characteristics of the study sample (country, mean age, % female, inclusion criteria), the year of baseline measurement, study duration, determinant measurement, outcome measurement, sample size, volunteering at baseline (%), volunteering at follow-up (%), and the results (association between the determinant(s) and the outcome). The same two reviewers independently assessed the risk of bias of the included articles by using the QUIPS (Quality In Prognosis Studies) tool13. The following
domains were assessed as potential sources for risk of bias: study participation, study
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attrition, measurement of the determinants and the outcome, study confounding and statistical analysis and reporting (see Appendix 2). Overall disagreement was evaluated and expressed as percentage of agreement and kappa statistics14. In a
consensus meeting disagreements were discussed and resolved. If consensus could not be reached, a third reviewer (N.Sm.) made the final decision.
Statistical analysis
In case the results of at least two studies are available, meta-analyses were conducted, using the statistical program Comprehensive Meta-Analysis (3rd version).
If studies present several models, estimates from the most complete (fully adjusted) model were used. Odds Ratios (ORs) with 95% Confidence Intervals (CIs) were used, or if needed calculated using the supplemental material of Kuiper et al.15, to conduct
meta-analyses. When insufficient information was available for transforming effect sizes to ORs with 95% CIs, study authors were contacted to obtain the missing information.
In case articles used the same study sample, a-priori defined criteria were used to select the study for the meta-analysis. In order of importance and for each determinant separately, articles were selected based on (a) outcome used in the study (‘formal voluntary work’ was preferred above ‘mixed type of voluntary work’), (b) measurement of the determinant (the determinant measurement was most comparable to other included studies), (c) study sample (the study sample that was the most comparable to the study samples of included studies in the meta-analysis, in terms of the proportion of volunteers at baseline, the age range of participants at baseline, and inclusion criteria for the baseline study sample), (d) sample size (the study with the largest sample size was preferred over smaller studies), and (e) number of determinants quantitatively measured in the study. In case articles presented both a static (e.g. being married) as well as a change score (e.g. transition into marriage) for a certain determinant, the score that is most comparable to the scores used in other included studies for this determinant was used. A random effect method was applied to calculate pooled effect sizes10.
Meta-regression and subgroup analyses
Heterogeneity between studies was assessed by using the Index of Inconsistency (I2)16. In case of substantial heterogeneity (I2 > 50%), sources of heterogeneity between
studies were explored by conducting either subgroup analysis (in case < 10 studies
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are available) or univariable random-effects meta-regression10 (in case ≥ 10 studiesare available) with regard to the following a-priori defined criteria: (a) outcome measurement (formal voluntary work versus mixed measure); (b) determinant measurement, based on (b1) measurement scale (continuous versus dichotomous scores), (b2) type of measurement (static versus change scores, because the presence of a certain event, (e.g. being married), may have a different association with the outcome than the transition into a certain event (e.g. transition into marriage)), and (b3) conceptual differences in the measurement of the determinant; (c) proportion of volunteers in the baseline study sample; (d) mean age at baseline, because some determinants may be important to a different extent for study samples for which participation in paid work is more or less common; (e) continent in which the study was performed (United States of America (USA), Europe, other), because differences in government regimes and culture may influence the association between a certain determinant and the outcome; (f) year of baseline measurement, because although the included studies were published between 2010 and 2015, the baseline measurement year varies substantially and determinants of participation in voluntary work may differ for different birth cohorts; (g) duration of follow-up (for time-variant variables only); and (h) the risk of bias for each methodological quality domain separately (low risk of bias versus high/unclear risk of bias).
Publication bias
The likelihood of publication bias was assessed graphically by constructing funnel plots for each determinant (in case at least ten studies were available) using the statistical program Comprehensive Meta-Analysis (3rd version). Asymmetry of the
funnel plots was tested using Egger’s method. Publication bias is likely if p<0.1017.
RESULTS
The search resulted in the identification of 13.225 records after removing duplicates. A total of 3774 records were published in 2010 or later. The selection process is presented in Fig. 1. Finally, 24 articles were included in the systematic review18–41.
Characteristics of the included articles are provided in Table 1. In Appendix 3 an overview of all determinants measured in included studies is provided.
Several articles were based on the same study samples. Four articles were based on data from the Survey of Midlife Development in the United States29,31,32,36. Another four
articles were based on data of the Health and Retirement Study22,23,38,39. Two articles
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used data from the Jena Study on Social Change and Human Development27,28.
Moreover, two articles used data from the Switzerland Household Panel33,34. Finally,
two articles were based on the American Changing Lives survey20,25.
Figure 1 Flow Diagram representing the selection process of articles
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41 DETERMINANTS OF PARTICIPATION IN VOLUNTARY WORK
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Ta b le 1 C ha rac te ri sti cs o f i n cl ud e d s tud ie s A ut h o r C oh or t C oun tr y S tu d y p op u la ti on 1 Mea n ag e 2 SD ag e 3 R a n g e ag e 3 (y e a rs ) F ema le (%) Y e a r o f ba se li n e 3 S tu d y du ra ti o n (y e a rs ) Wa ve s (n ) O u tc o m e O u tc o m e me a su remen t Ty p e o f vo lu n ta ry wo rk 4 S a mpl e si ze ( n ) V o lu n te e ri n g a t b a se li n e (%) V o lu n a t f o ll (%) A jr o u c h e t a l. 18 S R H LC 5 US A 6 A d u lt s a g e d ≥5 0 y 53 ,9 N. R . 7 50 -10 0 6 0 ,3 19 9 2 13 2 Vo lu n te e ri n g {N o v s. Y e s} “D o y o u d o a n y vo lu n te e ri n g? ” M ix e d 49 9 N. R . 32 ,3 B a rt e ls e t a l. 19 B HP S 8 UK 9 E m p lo ye d in d iv id u al s ag e d ≤ 6 0 y N. R . N. R . N. R . N. R . 19 9 1 16 11 Vo lu n te e ri n g {Y e s v s. N o } Vo lu n te e ri n g is m e as u re d a s “b e in g a ct iv e i n or ga ni za ti ons ” F o rm al 12 37 8 N. R . N. R . B e k ke rs 30 G INP S 10 NL 11 N. R . N. R . N. R . N. R . N. R . 20 02 4 3 - V o lu n te e r en g ag emen t - V o lu n te e r ce ss at io n Vo lu n te e ri n g is m e as u re d a s “b e in g a ct iv e a s a v o lu n te e r i n th e p as t y e ar ” M ix e d 123 3 12 ; 73 1 13 56 ,6 4 4 ,1 B ro e se v a n G roeno u & V a n T il b u rg 35 L A SA 14 NL A d u lt s a g e d b e tw e e n 5 5 an d 6 9 6 5 ,1 5 ,0 55-6 9 N. R . 19 9 2 15 / 20 02 16 6 3 17 Vo lu n te e ri n g {Y e s v s. N o } C u rr e n t vo lu n te e ri n g F o rm al 13 57 17 ; 13 8 8 18 38 ,0 17 / 4 5 ,0 18 N. R . 1 A ll i n cl u d e d s tu d ie s r e p re se n t ( su b g ro u p s o f) t h e g e n e ra l p o p u la ti o n . S p e ci fic at io n o f s u b g ro u p s i s p ro vi d e d h e re 2 M e as u re d a t b as e lin e , u n le ss d e n o te d o th e rw is e 3 R e p re se n ts t h e m e as u re m e n t i n t h e y e ar t h at i s u se d a s b as e lin e f o r t h e a n al ys is 4 Ty p e : F o rm al v o lu n te e ri n g (t h ro u g h a n o rg an iz at io n ), M ix e d ( n o d is ti n ct io n b e tw e e n f o rm al a n d i n fo rm al v o lu n te e ri n g , o r t yp e o f v o lu n te e ri n g ( fo rm al / in fo rm al ) n o t s p e ci fie d 5 S o ci al R e la ti o n s a n d H e al th o ve r t h e L ife C o u rs e 6 U n it e d S ta te s o f A m e ri c a 7 N o t R e p o rt e d 8 B ri ti sh H o u se h o ld P an e l S u rv e y 9 U n it e d K in g d o m 10 G iv ing in t he Ne the rl and s P anel S tu d y 11 T he Ne the rl and s 12 Vo lu n te e rs 13 N o n -v o lu n te er s 14 Lo n g it u d in al Ag in g S tu d y A m st e rd am 15 C o h o rt 1 16 C o h o rt 2 17 F o r ea ch c o h o rt 135747_Jacobien_Niebuur_BNW-def.indd 41 135747_Jacobien_Niebuur_BNW-def.indd 41 15-8-2020 17:27:1115-8-2020 17:27:1142 CHAPTER 2 C h o i & C h o u 36 MIDU S 18 US A E n g lis h sp e ak ing ad u lt s a g e d 55 -8 4 y a t w av e 2 w it h ≥1 t e le p h o n e in t h e h ou se h o ld N. R . N. R . N. R . 5 4 ,0 19 9 5 / 19 9 6 9 2 - V o lu n te e r en g ag emen t - V o lu n te e r ce ss at io n “O n a ve ra g e , ab o u t h o w m an y h o u rs p e r m o n th d o y o u s p e n d d o in g f o rm al vo lu n te e r w o rk ?” F o rm al 9 17 35 ,6 41 ,4 C ra m m & N ieboer 37 N .A. 19 NL O ld e r a d u lt s ag e d ≥ 70 y l iv in g i n Ro tt e rd am 7 7, 5 5 ,8 70 -1 0 1 57, 0 20 11 2 2 Vo lu n te e ri n g {Y e s v s. N o } Vo lu n ta ry act iv it ie s c arri e d o u t i n t h e p as t ye ar F o rm al 58 8 18 ,5 15 ,5 C u rl e t a l. 38 H RS 20 US A A du lt s ag e d ≥ 6 5 y r e p o rt e d b e in g a b le to d ri ve a t ba sel ine 73 ,8 6 ,5 N. R . 48 ,3 19 9 8 12 7 Vo lu n te e ri n g {Y e s v s. N o } V o lu n ta ry w o rk c ar ri e d o u t i n t h e p as t 1 2 m o n th s F o rm al 4788 34 ,6 N. R . C u rl e t a l. 39 H RS 21 US A R es p o n d e n ts an d s p ou se s, ag e d ≥ 6 5 y , ab le t o d ri ve at ba sel ine 73 ,9 21/ 71 ,5 22 5, 4 22 / 5 ,0 23 N. R . 50, 0 19 9 8 12 7 Vo lu n te e ri n g {Y e s v s. N o } V o lu n ta ry w o rk c ar ri e d o u t i n t h e p as t 1 2 m o n th s F o rm al 291 4 23 40, 0 22 / 41 ,5 23 N. R . E in o lf & P h il br ic k 40 P S ID 24 US A In d iv id u al s n e ve r m ar ri e d a t ba sel ine N. R . N. R . N. R . N. R . 20 03 2 2 -Vo lu n te e ri n g {Y e s v s. N o } -R e lig iou s vo lu n te e ri n g {Y e s v s. N o } “H o w o ft e n d id yo u v o lu n te e r a t o r t h ro u g h …. ” F o rm al 45 2 25 ; 61 0 26 R at e s a t b as e lin e a n d f u p a re n o t p re se n te d . A ra te s f o r t h e t w o w av e 25 ,3 % 27 ; 1 5 ,5 % 28 18 S u rv e y o f M id lif e D e ve lo p m e n t i n t h e U n it e d S ta te s 19 N o t app lic ab le 20 He al th a n d R e ti remen t S tu d y 21 Hu sb an d s 22 W iv e s 23 14 57 c o upl e s 24 P an e l S tu d y o f I n co m e D yn am ic s 25 M ale s 26 Fe m al e s 27 Vo lu n te e ri n g 28 R el ig io u s v o lu n te e ri ng 135747_Jacobien_Niebuur_BNW-def.indd 42 135747_Jacobien_Niebuur_BNW-def.indd 42 15-8-2020 17:27:1115-8-2020 17:27:11
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H a n k & E rli ng ha g en 41 S HAR E 29 11 Eu ro p e an co un tr ie s In d iv id u al s ag e d ≥ 50 y N. R . N. R . N. R . N. R . 20 0 4 / 20 0 5 2 2 - V o lu n te e r en g ag emen t - V o lu n te e r ce ss at io n “H av e y o u d o n e an y o f t h e se ac ti vi ti e s i n th e la st m o n th ?” - “d o n e v o lu n ta ry o r c h ar it y w o rk ” F o rm al 18 0 57 10 ,0 Joh n st on 20 AC L 30 US A In d iv id u al s ag e d 2 5 an d o ld e r liv in g i n t h e co n ti g u ou s US . 5 4 ,0 31 N. R . N. R . 5 4 ,0 19 8 6 16 4 - V o lu n te e ri n g {Y e s v s. N o } - R e lig io u s ins ti tu ti on vo lu n te e ri n g {Y e s v s. N o } - N o n re lig iou s ins ti tu ti on vo lu n te e ri n g {Y e s v s. N o } V o lu n te e r w o rk d o n e i n t h e l as t ye ar F o rm al 12 83 32; 9 83 33 ; 127 2 34 40, 0 L im & M a c G re g o r 21 FM 35 US A R es p o n d e n ts w h o r e p o rt th at t h e y d o n o t a tt e n d re lig iou s se rv ic e s o n a re gu la r b asi s 47, 3 16 ,0 N. R . 47, 0 20 0 6 5 2 Vo lu n te e ri n g {Y e s v s. N o } Vo lu n te e ri n g in t h e p as t 1 2 m on ths M ix e d 510 46 ,0 29 S u rv e y o f H e al th , A g e in g a n d R e ti re m e n t i n E u ro p e 30 A m e ri c an’ s C h an g in g L iv e s S tu d y 31 Appr o xi m at e ly 32 V o lun te e ri n g s ampl e 33 R e lig io us ins ti tu ti on v o lun te e ri n g s am pl e 34 N onr e lig io u s i ns ti tu ti on v o lun te e ri n g s ampl e 35 Fa it h M at te rs S u rv e y 135747_Jacobien_Niebuur_BNW-def.indd 43 135747_Jacobien_Niebuur_BNW-def.indd 43 15-8-2020 17:27:1115-8-2020 17:27:1144 M c N amar a & G o n za le s 22 H RS 21 US A In d iv id u al s ag e d 5 0 - 8 0 63 ,0 36 N. R . N. R . 58 ,7 20 0 0 / 20 0 1 8 5 -Vo lu n te e r en g ag emen t -Vo lu n te e r ce ss at io n “H av e y o u sp e n d a n y t im e in t h e p as t 1 2 m o n th s d o in g vo lu n te e r w o rk fo r c h ar it ab le or ga ni za ti ons ?” F o rm al 461 1 37; 29 61 38 45 ,1 M ike e t a l. 23 H RS 21 US A In d iv id u al s ≥5 0 y , n o t vo lu n te e ri n g an d c u rr e n tl y w o rk in g / u n e m p loye d / re ti re d 71 ,9 10 ,3 7 N. R . 5 4 ,0 20 0 6 / 2008 2 2 Vo lu n te e ri n g {Y e s v s. N o } “H av e y o u s p e n t an y t im e i n th e p as t y e ar vo lu n te e ri n g? ” M ix e d 50 17 0, 0 N e sbi t 24 P S ID 25 US A H ou se h o ld he ad s a nd th e ir s p o u ses 4 4 ,0 N. R . N. R . 55 ,0 20 03 2 2 -R e lig iou s vo lu n te e ri n g {Y e s v s. N o } -S e cu la r vo lu n te e ri n g {Y e s v s. N o ) V o lu n te e ri n g i n th e l as t y e ar F o rm al 11 29 9 39; 113 5 4 40 27, 0 O k u n e t a l. 25 AC L 31 US A In d iv id u al s ag e d ≥ 6 5 y, r e p o rt e d vo lu n te e ri n g in t h e p as t ye ar 71 ,9 5 ,5 N. R . 71 ,0 19 8 6 3 2 Vo lu n te e r ce ss at io n H av in g d o n e vo lu n te e r w o rk in t h e l as t 1 2 m on ths F o rm al 380 10 0 ,0 P a rk in son 26 A L SW H 41 A u st ra lia W o men a g e d 70 -7 5 y N. R . N. R . N. R . 10 0 19 9 6 9 4 Vo lu n te e ri n g {Y e s v s. N o } “D o y o u d o an y v o lu n te e r w o rk f o r a n y communi ty o r s o ci al or ga ni za ti ons ?” M ix e d 7088 N. R . 36 M e an a g e i s m e as u re d o ve r a ll i n cl u d e d w av e s 37 O u tc o me en g ag emen t 38 O u tc o m e c e ss at io n 39 R el ig io u s v o lu n te e ri ng 40 S e cu la r v o lu n te e ri n g 41 A u st ra lian L o n g it u di n al S tu d y O n W o m e n s H ea lt h 135747_Jacobien_Niebuur_BNW-def.indd 44 135747_Jacobien_Niebuur_BNW-def.indd 44 15-8-2020 17:27:1115-8-2020 17:27:11
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P a vl o va & S ilber e is en 2 7 Je na st u d y 42 G e rm any In d iv id u al s ag e d 1 6 -4 3 an d 5 6 -7 5 ye ar s 38 ,1 43 / 6 0, 2 44 3 ,9 4 4 / 3 ,9 45 N. R . 57, 4 44 / 4 4 ,6 45 20 0 5 44 / 20 0 9 45 1 2 -Vo lu n te e r en g ag emen t -Vo lu n te e r ce ss at io n P ar ti cip at io n in vo lu n ta ry w o rk in t h e p as t 1 2 m on ths F o rm al 156 0 44; 518 45 20 ,6 44; 34 .5 45 P a vl o va & S ilber e is en 28 Je na S tu d y 43 G e rm any In d iv id u al s ag e d 5 6 -7 5 ye ar s 6 5 ,9 5 ,8 56 -7 6 52, 4 20 0 9 1 2 Vo lu n te e ri n g {Y e s v s. N o } P ar ti cip at io n in vo lu n ta ry w o rk in t h e p as t 1 2 m on ths F o rm al 6 02 32, 5 S o n & W il son 29 MIDU S 21 US A E n g lis h sp e ak ing ad u lt s a g e d 25 -7 4 y , liv in g i n t h e co te rm in ou s US 42, 8 12, 5 N. R . 55 ,0 19 9 5 10 2 Vo lu n te e ri n g {Y e s v s. N o } “O n a ve ra g e , ab o u t h o w m an y h o u rs d o yo u s p e n d p e r m o n th d o in g vo lu n te e r w o rk ?” F o rm al 32 57 39 ,0 S o n & W il son 31 MIDU S 21 US A E n g lis h sp e ak ing ad u lt s a g e d 25 -7 4 y , liv in g i n t h e co te rm in ou s US 42, 8 12, 5 N. R . 55 ,0 19 9 5 10 2 Vo lu n te e ri n g {Y e s v s. N o } “O n a ve ra g e , ab o u t h o w m an y h o u rs d o yo u s p e n d p e r m o n th d o in g vo lu n te e r w o rk ?” F o rm al 32 57 39 ,0 S o n & W il son 32 MIDU S 21 US A E n g lis h sp e ak ing ad u lt s a g e d 25 -7 4 y , liv in g i n t h e co te rm in ou s US 42, 8 12, 5 N. R . 55 ,0 19 9 5 10 2 Vo lu n te e ri n g {Y e s v s. N o } “O n a ve ra g e , ab o u t h o w m an y h o u rs d o yo u s p e n d p e r m o n th d o in g vo lu n te e r w o rk ?” F o rm al 32 57 39 ,0 42 Je n a S tu d y o n S o cia l C h an g e an d Hu m an D e ve lo pm e n t 43 S am p le 1 A g e g ro u p 3 0 -4 3 44 S am p le 2 A g e g ro u p 5 6 -7 5 135747_Jacobien_Niebuur_BNW-def.indd 45 135747_Jacobien_Niebuur_BNW-def.indd 45 15-8-2020 17:27:1115-8-2020 17:27:1146 CHAPTER 2 V oo rpo st e l & C o ff é 33 S HP 45 S w it ze r-lan d A d u lt s a g e d 18 - 6 0 y 43 ,6 46 /4 4 ,2 47 12 ,0 47 /11 ,8 48 18 -6 0 55 ,0 1999 8 9 Vo lu n te e ri n g {Y e s v s. N o } “D o y o u h av e h o n o rar y o r vo lu n ta ry ac ti vi ti e s w it h in a n as so ci ati on, a n o rg an iz at io n o r an ins ti tu ti on ?” F o rm al 81 8 5 48 42, 5 49 / 3 1, 6 50 39 ,5 V oo rpo st e l & C o ff é 34 S HP 46 S w it ze r-lan d A d u lt s a g e d 18 – 2 6 y , n o ch an g e i n p ar tn e rsh ip o f p ar e n ts du ri n g s tu d y 21 ,0 2, 4 18 -2 6 47, 0 1999 10 11 Vo lu n te e ri n g {Y e s v s. N o } “D o y o u h av e h o n o rar y o r vo lu n ta ry ac ti vi ti e s w it h in a n as so ci ati on, a n o rg an iz at io n o r an ins ti tu ti on ?” F o rm al 319 9 51 V o lu n te e ri n g r at e s a b as e lin e a n d f o llo w -u n o t p re se n te d . T h e a o ve ra ll v o lu n te e ri n g r th e t w o w av e s i s 3 4 ,9 45 S w it ze rl an d H ou se h o ld P an e l 46 M al e s, m e as u re d a t f o llo w -u p 47 F e m al e s, m e as u re d a t f o llo w -u p 48 36 9 2 m al e s a n d 4 49 3 f e m al e s 49 M ale s 50 Fe m al e s 51 17 8 8 r e sp o n d e n ts a n d t h e ir m o th e rs a n d 1 33 1 r e sp o n d e n ts a n d t h e ir f at h e rs 135747_Jacobien_Niebuur_BNW-def.indd 46 135747_Jacobien_Niebuur_BNW-def.indd 46 15-8-2020 17:27:1115-8-2020 17:27:11
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Likelihood of risk of bias
The results of the risk of bias assessment of included studies are presented in Table 2. The risk of bias varied substantially. Most methodological flaws (i.e. high risk of bias) were found for (2a) adequate follow-up rate (62.5% high risk of bias), and (1b) adequate participation rate (29.2% high risk of bias). The inter-rater agreement was good (agreement 91.7% (484/528); kappa statistic: 0.78)14.
Determinants of participation in voluntary work
Meta-analyses were conducted for a total of 20 determinants (see Appendix 4). For each determinant, all studies reporting an association between the determinant and the outcome are listed in the appendix, as well as the studies selected for inclusion in the meta-analysis.
Demographic factors
The following demographic factors are studied in relationship to participation in voluntary work: age, gender, ethnicity, marital status and parental status. Forest plots for all demographic factors are presented in multi panel Fig. 2 below.
Age The mean age at baseline of the studies included in the meta-analysis varied from 42.8 years (range 25 to 74 years)32 to 77.5 years (range 70 to 101 years)37. The results
of the meta-analysis are heterogeneous (see Fig. 2a). Six studies (11,21,24,26,30,36) (out of eleven) found that older people are less likely to volunteer, no associations in the opposite direction were found. Sources of heterogeneity were explored by conducting meta-regression analyses and subgroup analyses (see Table 3).
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48 Ta b le 2 R is k o f B ia s t ab le ( B as e d o n Q U IP S *) A ut h o r 1. S tu d y p a rti ci p a ti o n 2 . S tu d y a ttr iti o n 3 . D e ter m inan t me a su remen t 4 . O u tc o m e me a su remen t 5 . S tu d y c o n foun di n g 6 . S ta ti st ic a l ana ly si s an d re p or ti n g 5 a . Co n fo u nd e rs m eas u re d 5d . Co n fo u nd e rs a c c o u n te d f o r i n a n a ly si s 1a . C onsec uti ve seri es o f p arti cip an ts 1b . Ad eq ua te p art ic ip ati on r ate ( >70 %) 2a . Ad eq ua te f oll ow -u p ra te ( ≥ 80 %) 2b . No i mp ort an t diff ere nc es b etw ee n pa rti cip an ts and dro p-ou t 3a . ≥70 % co mp le te d ata f or e ac h de te rm in an t 3b . Me th od a nd s ett in g of t he m ea su re me nt i s th e sa me f or a ll s tu dy p art ic ip an ts 3c . Appr opr iate m eth od s o f im pu ta tio n 4a . Ou tco me m ea su re me nt t ru ly c ap tu re s volu nte eri ng 4b . Me th od a nd s ett in g of m ea su re me nt i s th e sa me f or a ll s tu dy p art ic ip an ts 5a 1. A ge 5a 2. S ocioe co no mic Sta tu s 5a 3. G en de r 5a 4. P art ic ip ati on i n vo lu nta ry w ork a t ba se lin e 5b . Me th od a nd se tti ng of me asu remen t is t he s am e fo r all s tu dy p art ic ip an ts 5c . Appr opr iate me th od s o f im pu ta tio n 5d 1. A ge 5d 2. S ocioe co no mic Sta tu s 5d 3. G en de r 5d 4. P art ic ip ati on i n vo lu nta ry w ork a t ba se lin e 6a . Sta tis tic al m od el a de qu ate f or s tu dy d esi gn 6b . No o ve rfit tin g 6c . No s ele cti ve r ep ort in g of r esu lts A jr o u c h e t a l. 18 + + -? + + N .A. 52 + + + + + -+ N .A. + + + -+ + + B a rt e ls e t a l. 19 + ? ? ? ? + ? + + -+ + + + ? -+ + + + + + B e k ke rs 30 -? -+ ? + ? + + + + + + + ? -+ + + B roe se v an G roeno u & V a n T il b u rg 35 + -? ? + ? + + + + + + + ? + + + + + + + C h o i & C h o u 36 + -+ ? + ? + + + + + + + ? + + + + + +/-53 + C ram m & N ieboer 37 -? + N .A. + + + + + + + N .A. + + + + + -+ C u rl e t a l. 38 + ? ? ? + + N .A. + + + + + + + N .A. + + + + + + + C u rl e t a l. 39 + ? ? ? + + N .A. + + + + + + + N .A. + + + + + + + 52 * Q U IP S : Q u al it y o f P ro g n o si s S tu d ie s i n S ys te m at ic R e vi ew s. A ss e ss m e n t: + (Y e s) (r e p re se n ts lo w r is k o f b ia s) ; (N o ) ( re p re se n ts h ig h r is k o f b ia s) ; ? (U n cl e ar ) ( re p re se n ts u n ce rt ai n r is k o f b ia s, in su ffi ci e n t i n fo rm at io n w as a va ila b le t o a ss e ss t h e r is k o f b ia s) N o t App lic ab le 53 F o r th e o u tc o m e vo lu n te e r e n g ag e m e n t (s ta rt in g ) t h e re is n o o ve r fit ti n g , s o lo w ri sk o f b ia s, b u t fo r th e o u tc o m e vo lu n te e r ce ss at io n (q u it ti n g ), th e re is sl ig h t o ve r fit ti n g o f th e m o d e l, so h ig h ri sk o f b ia s. 135747_Jacobien_Niebuur_BNW-def.indd 48 135747_Jacobien_Niebuur_BNW-def.indd 48 15-8-2020 17:27:1115-8-2020 17:27:11
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Ta b le 2 C o nt in u ed E in o lf & P h il b ri c k 40 + ? + ? ? + ? + + + + + + + ? + + + + + + + H an k & E rli ng h a g en 41 + -? ? ? ? + ? + + + + ? ? + + + + + + + Joh n st on 20 + -? ? + ? + + + + + + + ? -+ + + + + + L im & M a c G re g o r 21 + ? -? ? + ? + + + + + + + ? + + + + + + + M c N a m a ra & G o n za le s 22 + ? ? ? + + + + + + + + + + + + + + + + + + M ike e t a l. 23 + ? ? ? + + N .A. + + + + + + + N .A. + + + + + + + N e sbi t 24 + ? ? ? ? + ? + + + + + + + ? + + + + + + + O k u n e t a l. 25 + ? ? ? + + N .A. + + + + + + + N .A. + + + + + + + P a rk in son 26 + ? -? ? + ? + + + + + + + ? + + + + + + + P a vl o va & S ilber e is en 2 7 + +/-54 ? 55 -/+ 56 + + + + + + + + + + + + + + + + + + P a vl o va & S ilber e is en 28 + -+ + + + + + + + + + + + + + + + + + + S on & W il son 29 + + -? ? + + + + + + + + + + + + + + + + + S on & W il son 31 + + -? ? + + + + + + + + + + + + + + + + + S on & W il son 32 + + -? ? + + + + + + + + + + + + + + + + + V o o rp o st e l & C o ff é 33 + ? -? ? + ? + + + + + + + ? + + + + + + + V o o rp o st e l & C o ff é 34 + ? -? ? + ? + + + + + + + ? + + + + + + + 54 B as e lin e p ar ti ci p at io n i n t h e fi rs t s am p le ( ag e g ro u p 1 6 -4 3) w as a d e q u at e ( 7 7 % ), b u t t h e b as e lin e p ar ti ci p at io n i n t h e s e co n d s am p le ( ag e g ro u p 5 6 -7 5) n o t ( 52 ,9 % ). 55 N o i n fo rm at io n i s p ro vi d e d o n t h e f o llo w -u p r at e s. H o w e ve r, t h e s e co n d s am p le ( ag e g ro u p 5 6 -7 5) i s t h e s am e a s t h e s am p le u se d i n P av lo va e t a l. 2 0 16 a n d a tt ri ti o n i s h ig h e r t h an 2 0 % . 56 A tt ri ti o n i n t h e fi rs t s am p le ( ag e g ro u p 1 6 -4 3) w as s e le ct iv e w .r. t. v o lu n te e ri n g a t T 1, f o r t h e s e co n d s am p le ( ag e g ro u p 5 6 -7 5) a tt ri ti o n w as n o t s e le ct iv e w .r. t. v o lu n te e ri n g a t T 1. 135747_Jacobien_Niebuur_BNW-def.indd 49 135747_Jacobien_Niebuur_BNW-def.indd 49 15-8-2020 17:27:1215-8-2020 17:27:1250 Ta b le 3 U n iv ar ia te r an d o m e ff e ct s m e ta -r e g re ss io n ( m e th o d s o f m o m e n ts ) a n d s u b g ro u p a n al ys e s f o r A G E S u bg rou p a na ly se s R esu lt s f ro m m e ta -r e gr es si o n R esu lt s H e ter o g ene it y V ar iab le S u bg rou p N u mb e r o f s tu di e s OR 9 5% C I P -v a lu e I 2 Coe ffic ien t SD P -v a lu e O u tc o m e me a su remen t M ix e d 2 0 .9 8 6 0 .9 59 – 1 .0 13 0 .0 37 77% R e fer enc e F or ma l 9 ( 12 d iff e re n t s am p le s) 0 .9 6 9 0 .9 46 – 0 .9 9 2 0 .000 8 9% -0 .0 16 8 0. 0 251 0 .5 04 D e ter m in an t me a su remen t D ic ho to mo u s 1 ( 2 d iff e re n t s am p le s) 0. 48 5 0 .3 8 5 – 0 .6 11 0. 24 8 2 5% R e fer enc e C o n ti n u o u s 10 ( 12 d iff e re n t s am p le s) 0 .9 83 0 .9 6 9 – 0 .9 9 6 0 .000 78% 0 .7 12 2 0 .10 14 0 .000 P ro p o rt io n o f v o lu n te e rs ( % ) i n b a se li n e st u d y s a m p le C on tin u o u s 10 57 (1 3 d iff e re n t s am p le s) 0 .97 0 0 .9 50 – 0 .9 9 1 0 .000 8 8% 0 .0000 0 .000 1 0 .59 1 0 – 1 0 0 % 9 ( 11 d iff e re n t s am p le s) 0 .9 8 5 0 .9 71 – 0 .9 9 9 0 .000 79 % R e fer enc e 0% 1 0. 4 40 0 .3 43 – 0 .5 6 5 N .A. N .A. -0 .8 0 53 0 .12 92 0 .000 10 0% 2 0 .74 7 0 .4 4 4 – 1 .2 56 0 .0 01 91 % -0 .0 50 0 0 .0 292 0 .0 87 M e a n a g e a t b a se li n e C on tin u o u s 10 58 (1 2 d iff e re n t s am p le s) 0 .9 83 0 .9 6 9 – 0 .9 9 6 0 .000 78% -0 .0000 0 .0000 0 .20 0 ≤ 5 5 y e ar s 5 ( 6 d iff e re n t s am p le s) 0 .9 9 1 0 .9 75 – 1 .0 0 7 0 .000 79 % R e fer enc e > 5 5 y e ar s 6 ( 8 d iff e re n t s am p le s) 0 .9 4 4 0 .9 0 4 – 0 .9 8 6 0 .000 8 9% -0 .0 296 0 .01 9 8 0 .1 35 Co n ti nen t US A 6 0 .97 8 0 .9 59 – 0 .9 9 8 0 .0 01 77% R e fer enc e Eu ro p e 5 ( 8 d iff e re n t s am p le s) 0 .9 6 6 0 .9 33 – 1 .0 0 0 0 .000 91 % -0 .0 02 6 0 .0 210 0 .9 0 0 57 T h e s tu d y o f A jr o u ch e t a l. ( 20 14 ) i s n o t i n cl u d e d i n t h is a n al ys is , b e c au se t h e p ro p o rt io n o f v o lu n te e rs ( % ) i n t h e b as e lin e s tu d y s am p le i s n o t r e p o rt e d . 58 T h e s tu d y o f H an k & E rl in g h ag e n ( 20 10 ) i s n o t i n cl u d e d i n t h is a n al ys is , b e c au se t h e m e an a g e a t b as e lin e i s n o t r e p o rt e d . 135747_Jacobien_Niebuur_BNW-def.indd 50 135747_Jacobien_Niebuur_BNW-def.indd 50 15-8-2020 17:27:1215-8-2020 17:27:12
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Ta b le 3 C o nt in u ed S u bg rou p a na ly se s R esu lt s f ro m m e ta -r e gr es si o n R esu lt s H e ter o g ene it y V ar iab le S u bg rou p N u mb e r o f s tu di e s OR 9 5% C I P -v a lu e I 2 Coe ffic ien t SD P -v a lu e Y e ar o f b a seli ne me a su remen t C on tin u o u s 11 ( 14 d iff e re n t s am p le s) 0 .9 8 9 0 .9 8 4 – 0 .9 9 5 0 .000 87 % 0 .000 6 0 .0 01 4 0. 6 8 6 < 2 0 0 6 8 ( 10 d iff e re n t s am p le s) 0 .97 0 0 .9 48 – 0 .9 9 3 0 .000 91 % R e fer enc e ≥ 2 0 0 6 3 ( 4 d iff e re n t s am p le s) 0 .9 75 0 .9 59 – 0 .9 9 1 0 .3 8 8 1% 0 .0 110 0 .02 30 0 .6 31 R is k o f b ia s i te m s S tu d y p a rt ici p a ti o n U n cl ear / h ig h ri sk o f b ia s 9 ( 12 d iff e re n t s am p le s) 0 .97 5 0 .9 56 – 0 .9 9 5 0 .000 8 8% R e fer enc e L o w r is k o f b ia s 2 0. 8 58 0 .6 23 – 1 .1 9 2 0 .000 93 % -0. 0 0 9 9 0 .03 15 0 .7 5 4 S tu d y c o n fou n di n g U n cl ear / h ig h ri sk o f b ia s 1 1. 000 0 .9 8 1 – 1 .0 20 N .A. N .A. R e fer enc e L o w r is k o f b ia s 10 ( 13 d iff e re n t s am p le s) 0 .97 0 0 .9 50 – 0 .9 9 1 0 .000 8 8% -0 .03 03 0 .03 31 0 .3 6 0 135747_Jacobien_Niebuur_BNW-def.indd 51 135747_Jacobien_Niebuur_BNW-def.indd 51 15-8-2020 17:27:1215-8-2020 17:27:1252
The meta-regression shows that differences in the proportion of volunteers in the baseline sample affect the association between age and participation in voluntary work. The negative coefficient from the meta-regression (-0.8053, p = 0.000) shows that the inverse association between age and the likelihood to volunteer is stronger in the non-volunteer sample than in the subgroup of samples in which the proportion of volunteers lies between 0 and 100%. Therefore, the results indicate that the likelihood to participate in voluntary work declines with age, and that especially the likelihood to take-up voluntary work (for individuals not volunteering at baseline) strongly decreases with age.
Gender (female) Two studies (out of eleven) included in the meta-analysis did not report the percentage of females in the baseline study sample35,41. The percentage
of females in the baseline study samples of the other included studies ranged from 44.6% (32) to 71.0%25 (heterogeneous results; see Fig. 2b).
The results of the meta-regression (Table 4) showed that differences in the continent (Europe versus USA) of the study sample explain heterogeneity in the association between gender and participation in voluntary work.
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Ta b le 4 U n iv ar ia te r an d o m e ff e ct s m e ta -r e g re ss io n ( m e th o d s o f m o m e n ts ) a n d s u b g ro u p a n al ys e s f o r G E N D E R ( fe m al e ) S u bg rou p a na ly se s R esu lt s f ro m m e ta -r e gr es si o n R esu lt s H e ter o g ene it y V ar iab le S u bg rou p N u mb e r o f s tu di e s OR 9 5% C I P -v a lu e I 2 Coe ffic ien t SD P -v a lu e O u tc o me me a su remen t M ix e d 2 1. 22 4 0 .8 9 5 – 1 .6 74 0. 8 0 0 0% R e fer enc e F or ma l 9 ( 13 d iff e re n t s am p le s) 1. 0 61 0 .9 0 7 – 1 .2 43 0 .000 8 9% -0 .1 42 4 0 .2 37 9 0 .5 50 P ro p o rt io n o f v o lu n te e rs (% ) i n b a se li n e s tu d y sa mp le C on tin u o u s 9 59 (1 3 d iff e re n t s am p le s) 1.0 9 9 0 .9 17 – 1 .3 17 0 .000 8 9% 0 .000 4 0 .000 3 0 .17 7 0 – 1 0 0 % 8 1. 03 8 0 .8 0 5 – 1 .2 6 8 0 .000 93 % R e fer enc e 0% 2 ( 3 d iff e re n t s am p le s) 0 .9 18 0 .8 0 8 – 1 .0 43 0 .83 6 0% -0. 0 6 8 9 0 .2 26 6 0 .7 6 1 10 0% 3 ( 4 d iff e re n t s am p le s) 1.3 0 6 1. 0 0 0 – 1 .7 0 5 0. 2 9 6 19% 0 .2 9 26 0 .21 56 0 .17 5 M e a n a g e a t b a se li n e C on tin u o u s 10 60 (1 3 d iff e re n t s am p le s) 1. 10 9 0 .9 20 – 1 .3 37 0 .000 8 6% -0 .0000 0 .000 6 0 .9 52 ≤ 5 5 y e ar s 6 ( 8 d iff e re n t s am p le s) 1.1 36 0 .9 39 – 1 .37 4 0 .000 8 5% R e fer enc e > 5 5 y e ar s 6 (7 d iff e re n t s am p le s) 1. 02 3 0 .7 6 5 – 1 .3 6 7 0 .000 9 0% -0 .1 296 0 .16 9 5 0. 4 45 Co n ti nen t US A 6 1. 27 9 1. 12 0 – 1 .4 6 0 0 .0 63 52% R e fer enc e Eu ro p e 5 ( 9 d iff e re n t s am p le s) 0 .9 0 6 0 .7 70 – 1 .0 6 7 0 .000 77% -0 .3 53 1 0 .1 13 5 0 .0 02 59 T h e s tu d ie s o f A jr o u ch e t a l. ( 20 14 ) a n d V o o rp o st e l & C o ff é ( 20 14 ) a re n o t i n cl u d e d i n t h is a n al ys is , b e c au se t h e p ro p o rt io n o f v o lu n te e rs ( % ) i n t h e b as e lin e s tu d y s am p le i s n o t r e p o rt e d . 60 T h e s tu d y o f H an k & E rl in g h ag e n ( 20 10 ) i s n o t i n cl u d e d i n t h is a n al ys is , b e c au se t h e m e an a g e a t b as e lin e i s n o t r e p o rt e d . 135747_Jacobien_Niebuur_BNW-def.indd 53 135747_Jacobien_Niebuur_BNW-def.indd 53 15-8-2020 17:27:1215-8-2020 17:27:1254 Ta b le 4 C o nt in u ed S u bg rou p a na ly se s R esu lt s f ro m m e ta -r e gr es si o n R esu lt s H e ter o g ene it y V ar iab le S u bg rou p N u mb e r o f s tu di e s OR 9 5% C I P -v a lu e I 2 Coe ffic ien t SD P -v a lu e Y e a r o f b a se li n e me a su remen t C on tin u o u s 11 61 (1 5 d iff e re n t s am p le s) 1. 07 8 0 .9 31 – 1 .2 49 0 .000 8 8% 0 .0008 0 .01 26 0. 9 51 < 2 0 0 6 9 ( 11 d iff e re n t s am p le s) 1. 0 83 0 .9 24 – 1 .2 70 0 .000 91 % R e fer enc e ≥ 2 0 0 6 3 ( 4 d iff e re n t s am p le s) 1.0 8 4 0 .7 75 – 1 .5 16 0 .4 74 0% -0 .03 0 1 0 .23 34 0 .8 97 R is k o f b ia s i te m s S tu d y p a rt ici p a ti o n U n cl ear / h ig h ri sk o f b ia s 9 ( 11 d iff e re n t s am p le s) 1. 02 5 0 .8 71 – 1 .2 0 5 0 .000 8 9% R e fer enc e L o w r is k o f b ia s 3 ( 4 d iff e re n t s am p le s) 1. 28 8 1. 0 9 4 – 1 .5 15 0 .3 8 3 2% 0 .2 43 6 0 .18 0 9 0 .17 8 S tu d y c o n fou n di n g U n cl ear / h ig h ri sk o f b ia s 1 1. 174 0 .7 48 – 1 .8 42 N .A. N .A. R e fer enc e L o w r is k o f b ia s 10 ( 14 d iff e re n t s am p le s) 1. 07 3 0 .9 22 – 1 .2 50 0 .000 8 9% -0. 0 8 9 8 0 .3 302 0 .7 8 6 61 T h e st u d y o f B ro e se va n G ro e n o u & V an T ilb u rg (2 0 12 ) i n cl u d e s tw o d iff e re n t sa m p le s in th e an al ys e s. F o r o n e o f th e sa m p le s, th e ye ar o f b as e lin e m e as u re m e n t is 19 9 2, fo r th e o th e r sa m p le , th e ye ar o f b as e lin e m e as u re m e n t is 20 0 2. N o se p ar at e re su lt s fo r th e tw o sa m p le s ar e p ro vi d e d . I n th is sp e ci fic an al ys is , w e to o k 19 9 2 as th e ye ar o f b as e lin e m e as u re m e n t, al th o u g h th is ac tu al ly o n ly i s t h e c as e f o r t h e fi rs t s am p le . 135747_Jacobien_Niebuur_BNW-def.indd 54 135747_Jacobien_Niebuur_BNW-def.indd 54 15-8-2020 17:27:1215-8-2020 17:27:12
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The negative coefficient (-0.3531; p = 0.002) from the meta-regression for Europe (USA as reference group) shows that the likelihood of females (as opposed to males) to participate in voluntary work is higher in the USA than in Europe. In the studies conducted in the USA18,21,24,25,32,38, a positive association between being female andparticipation in voluntary work was found (OR: 1.279; 95%CI: 1.120 - 1.460; results are heterogeneous (I2 = 52%)). In the studies conducted in Europe27,34,35,37,41, no association
between gender and participation in voluntary work was found (OR: 0.906; 95%CI: 0.770 - 1.067; results are heterogeneous (I2 = 77%)). Having a closer look at the
subgroups of studies conducted in the USA and in Europe shows that (a) in Europe no consistent association between gender and participation in voluntary work was found (both positive as well as negative associations between gender and participation in voluntary work were found) whereas (b) in the subgroup of studies conducted in the USA, all odds ratios for the association between being female and participation in voluntary work are greater than one, indicating a greater likelihood of females (as opposed to males) to participate in voluntary work.
Ethnicity (white) The results of the studies investigating the association between ethnicity and participation in voluntary work are heterogeneous and inconsistent (see Fig. 2c).
Heterogeneity could be explained by conducting subgroup analyses for differences in (a) year of baseline measurement (no association for the studies with a baseline measurement after 200521,37 (OR: 1.743; 95%CI: 0.308 - 9.877) and (b) the risk of bias for
the domain study participation (no association for the studies with low risk of bias18,32
(OR: 1.101; 95%CI: 0.929 - 1.034). Forest plots are available upon request.
Marital status (married/partnered) The results of the meta-analysis for marital status are heterogeneous and inconsistent (see Fig. 2d).
Sources of heterogeneity were explored by conducting meta-regression and subgroup analyses (see Table 5).
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56 Ta b le 5 U n iv ar ia te r an d o m e ff e ct s m e ta -r e g re ss io n ( m e th o d s o f m o m e n ts ) a n d s u b g ro u p a n al ys e s f o r M A R IT A L S TA T U S ( m ar ri e d /p ar tn e re d ) S u bg rou p a na ly se s R esu lt s f ro m m e ta -r e gr es si o n R esu lt s H e ter o g ene it y V ar iab le S u bg rou p N u mb e r o f s tu di e s OR 9 5% C I P -v a lu e I 2 Coe ffic ien t SD P -v a lu e O u tc o me me a su remen t M ix e d 1 1.1 24 0 .6 8 2 – 1 .8 53 N .A. N .A. R e fer enc e F or ma l 9 ( 14 d iff e re n t s am p le s) 1. 053 0 .9 31 – 1 .1 9 2 0 .0 01 6 2% -0 .0 6 50 0 .3 0 6 7 0 .83 2 P ro p o rt io n o f v o lu n te e rs (% ) i n b a se li n e s tu d y sa mp le C on tin u o u s 9 6 2 (1 4 d iff e re n t s am p le s) 1. 0 87 0 .9 6 8 – 1 .2 21 0 .0 45 43% -0 .000 2 0 .000 2 0 .3 8 5 0 – 1 0 0 % 8 ( 9 d iff e re n t s am p le s) 1. 07 1 0 .9 17 – 1 .2 50 0 .0 01 70 % R e fer enc e 0% 2 ( 3 d iff e re n t s am p le s) 1.0 52 0 .9 0 2 – 1 .2 27 0 .3 8 1 0% 0 .04 6 8 0 .19 0 7 0 .8 06 10 0% 2 ( 3 d iff e re n t s am p le s) 1. 080 0 .5 6 4 – 2 .0 6 6 0 .17 5 43% -0 .1 253 0 .20 9 5 0 .5 50 M e a n a g e a t b a se li n e C on tin u o u s 8 63 (1 2 d iff e re n t s am p le s) 1. 147 1. 0 0 1 – 1 .3 15 0. 11 2 3 5% -0 .000 8 0 .000 4 0 .03 0 ≤ 5 5 y e ar s 6 ( 8 d iff e re n t s am p le s) 1.1 40 0 .9 11 – 1 .4 27 0 .000 76% R e fer enc e > 5 5 y e ar s 5 (7 d iff e re n t s am p le s) 0 .9 9 9 0 .9 13 – 1 .0 9 2 0 .53 9 0% -0 .1 47 7 0 .1 419 0 .3 0 0 Co n ti nen t US A 4 1.0 6 5 0 .8 70 – 1 .3 0 4 0 .04 9 6 2% R e fer enc e Eu ro p e 6 ( 11 d iff e re n t s am p le s) 1.0 5 4 0 .9 0 4 – 1 .2 30 0. 0 0 9 57 % -0 .0 10 6 0 .1 31 4 0 .93 6 Y e a r o f b a se li n e me a su remen t C on tin u o u s 10 ( 15 d iff e re n t s am p le s) 1.0 55 0 .9 37 – 1 .1 8 8 0 .0 02 59% 0 .0088 0. 0 0 9 6 0 .3 61 < 2 0 0 6 8 ( 11 d iff e re n t s am p le s) 1.0 55 0 .9 28 – 1 .1 9 9 0 .000 6 9% R e fer enc e ≥ 2 0 0 6 3 ( 4 d iff e re n t s am p le s) 1. 0 81 0 .7 42 – 1 .5 75 0. 52 2 0% 0 .02 9 5 0. 22 51 0. 8 9 6 6 2 T h e s tu d y o f B ar te ls e t a l. ( 20 13 ) i s n o t i n cl u d e d i n t h is a n al ys is , b e c au se t h e p ro p o rt io n o f v o lu n te e rs ( % ) i n t h e b as e lin e s tu d y s am p le i s n o t r e p o rt e d . 63 T h e s tu d ie s o f B ar te ls e t a l. ( 20 13 ) a n d H an k & E rl in g h ag e n ( 20 10 ) a re n o t i n cl u d e d i n t h is a n al ys is , b e c au se t h e m e an a g e a t b as e lin e i s n o t r e p o rt e d . 135747_Jacobien_Niebuur_BNW-def.indd 56 135747_Jacobien_Niebuur_BNW-def.indd 56 15-8-2020 17:27:1215-8-2020 17:27:12
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2
Ta b le 5 C o nt in u ed S u bg rou p a na ly se s R esu lt s f ro m m e ta -r e gr es si o n R esu lt s H e ter o g ene it y V ar iab le S u bg rou p N u mb e r o f s tu di e s OR 9 5% C I P -v a lu e I 2 Coe ffic ien t SD P -v a lu e D u ra ti o n o f fo llo w -u p C on tin u o u s 10 ( 15 d iff e re n t s am p le s) 1.0 55 0 .9 37 – 1 .1 8 8 0 .0 02 59% -0 .0 111 0 .01 15 0 .3 35 ≤ 3 y e ar s 3 (7 d iff e re n t s am p le s) 0 .9 9 0 0 .8 30 – 1 .1 8 0 0 .2 74 2 0% R e fer enc e 4-7 y ear s 2 1.0 9 6 0 .8 22 – 1 .4 63 0 .9 0 5 0% 0 .07 76 0 .23 15 0 .7 37 ≥ 8 y e ar s 5 ( 6 d iff e re n t s am p le s) 1. 0 82 0 .8 9 6 – 1 .3 0 6 0 .000 81 % 0 .058 0 0 .1 49 9 0. 6 9 9 R is k o f b ia s i te m s S tu d y p a rt ici p a ti o n U n cl ear / h ig h ri sk o f b ia s 9 ( 12 d iff e re n t s am p le s) 1. 0 04 0 .8 97 – 1 .1 24 0 .01 9 52% R e fer enc e L o w r is k o f b ia s 2 ( 3 d iff e re n t s am p le s) 1.3 53 1. 10 5 – 1 .6 57 0 .47 8 0% 0 .3 10 6 0 .1 563 0 .0 47 S tu d y c o n fou n di n g U n cl ear / h ig h ri sk o f b ia s 2 0. 8 4 6 0 .7 6 6 – 0 .9 35 0 .7 63 0% R e fer enc e L o w r is k o f b ia s 8 ( 13 d iff e re n t s am p le s) 1.1 15 0 .9 9 4 – 1 .2 52 0 .0 83 3 8% 0 .280 3 0 .1 11 3 0. 0 12 135747_Jacobien_Niebuur_BNW-def.indd 57 135747_Jacobien_Niebuur_BNW-def.indd 57 15-8-2020 17:27:1215-8-2020 17:27:1258
The results of the meta-regression show that differences in (a) mean age at baseline and (b) the risk of bias for the domains study participation and study confounding affect the association between marital status and participation in voluntary work. Firstly, the pooled estimate of the subgroup of the eight studies20,21,27,32,33,35,37,38 for which
information on the mean age at baseline is available, shows that married people are more likely to participate in voluntary work than unmarried people (OR: 1.147; 95%CI: 1.001 - 1.315; results are homogenous (I2= 35%)). The negative coefficient (-0.0008;
p = 0.030) from the meta-regression shows that the positive association between being married and participation in voluntary work declines with age; i.e. being married as a determinant of participation in voluntary work declines in importance with age. Secondly, the positive coefficients from the meta-regression for the risk of bias domains study participation (0.3106; p = 0.047) and study confounding (0.2803; p = 0.012) show that the association between being married and participation in voluntary work is stronger in studies with low risk of bias on these domains than for the studies with unclear/high risk of bias.
Although we did not find an overall association between marital status and participation in voluntary work, several subgroups of studies point towards a positive association between being married/partnered and the likelihood to volunteer. The meta-regression shows that as age increases, the association between being married/partnered and the likelihood to participate in voluntary work gets less strong. Our findings are in line with earlier research, showing that being married is positively associated to participation in voluntary work; but associations between marital status and volunteering after retirement are inconsistent9.
Parental status The results of the studies investigating the association between parental status and participation in voluntary work are heterogeneous (see Fig. 2e). Heterogeneity could not be explained by conducting subgroup analyses. Three studies19,20,33 (out of five) found a positive association between having children and
participation in voluntary work and no negative associations were found. Although, no firm conclusion can be drawn from these results, the results seem to indicate that parents with children in their household are more likely to volunteer.
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Two articles24,33 reported estimates for the association between a transition intoparenthood and participation in voluntary work. The pooled estimate of these two studies shows that individuals who recently had a child were less likely to participate in voluntary work than individuals who did not experience the birth of a child in the household recently (OR: 0.617; 95%CI: 0.487 to 0.781) (see Fig. 2f).
Figure 2 Forest plots for demographic factors
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Figure 2 Continued
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Figure 2 Continued
Socioeconomic status Two factors related to socioeconomic status are studied in
relationship to participation in voluntary work. Meta-analyses were conducted for educational attainment as well as income. The forest plots are presented in multi panel Fig. 3 below.
Educational attainment The results of the meta-analysis for educational attainment are heterogeneous (see Fig. 3a). Seven studies18,24,26,32,35,38,41 (out of thirteen) found
that higher educated individuals are more likely to participate in voluntary work, no associations in the opposite direction were found. Sources of heterogeneity were explored by conducting meta-regression and subgroup analyses (see Table 6).
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62 Ta b le 6 U n iv ar ia te r an d o m e ff e ct s m e ta -r e g re ss io n ( m e th o d s o f m o m e n ts ) a n d s u b g ro u p a n al ys e s f o r E D U C A T IO N A L A T TA IN M E N T S u bg rou p a na ly se s R esu lt s f ro m m e ta -r e gr es si o n R esu lt s H e ter o g ene it y V ar iab le S u bg rou p N u mb e r o f s tu di e s OR 9 5% C I P -v a lu e I 2 Coe ffic ien t SD P -v a lu e O u tc o me me a su remen t M ix e d 3 1.19 9 0 .9 8 5 – 1 .4 6 0 0 .000 9 0% R e fer enc e F or ma l 10 ( 14 d iff e re n t s am p le s) 1.1 53 1. 0 9 4 – 1 .2 15 0 .000 81 % -0 .03 35 0 .0 59 1 0. 571 D et e rm in a n t me a su remen t D ic ho to mo u s 5 ( 9 d iff e re n t s am p le s) 1. 256 1. 0 0 1 – 1. 577 0 .000 8 6% R e fer enc e C o n ti n u o u s 8 1.1 30 1. 0 8 2 – 1 .1 79 0 .000 8 0% -0 .0 92 2 0 .0 57 9 0 .111 P ro p o rt io n o f v o lu n te e rs (% ) i n b a se li n e s tu d y sa mp le C on tin u o u s 9 64 (1 3 d iff e re n t s am p le s) 1. 16 2 1. 10 4 – 1 .2 23 0 .000 79 % -0 .000 1 0 .000 1 0 .17 6 0 – 1 0 0 % 10 1. 147 1. 088 – 1 .2 08 0 .000 87 % R e fer enc e 0% 2 ( 3 d iff e re n t s am p le s) 1. 56 4 1. 32 1 – 1 .8 53 0 .6 67 0% 0 .3 080 0 .1 10 0 0 .0 05 10 0% 3 ( 4 d iff e re n t s am p le s) 1. 17 1 0 .8 70 – 1 .5 77 0 .02 4 6 8% 0 .008 3 0. 0 72 0 0 .9 0 8 M e a n a g e a t b a se li n e C on tin u o u s 10 65 (1 3 d iff e re n t s am p le s) 1. 111 1. 0 6 4 – 1 .1 6 1 0 .000 77% 0 .000 1 0 .000 1 0 .4 93 ≤ 5 5 y e ar s 7 ( 8 d iff e re n t s am p le s) 1.1 48 1. 0 25 – 1 .2 8 6 0 .000 8 4% R e fer enc e > 5 5 y e ar s 7 ( 9 d iff e re n t s am p le s) 1. 203 1. 12 8 – 1 .2 8 4 0 .000 8 4% 0. 0 71 1 0 .0 576 0 .2 17 Co n ti nen t US A 6 1.1 4 4 1. 0 75 – 1 .2 18 0 .000 8 4% R e fer enc e Eu ro p e 6 ( 10 d iff e re n t s am p le s) 1. 18 6 1. 0 55 – 1 .3 33 0 .000 77% 0 .0 110 0 .0 59 8 0. 8 5 4 A us tra lia 1 1. 43 0 1. 28 3 – 1 .5 9 4 N .A. N .A. 0. 2 16 4 0 .10 4 9 0 .03 9 64 T h e st u d ie s o f A jr o u ch e t a l. (2 0 14 ), B ar te ls e t a l. (2 0 13 ), P ar ki n so n (2 0 10 ) a n d V o o rp o st e l & C o ff é (2 0 14 ) a re n o t i n cl u d e d in th is an al ys is , b e c au se th e p ro p o rt io n o f v o lu n te e rs (% ) i n th e b as e lin e st u d y s am p le i s n o t r e p o rt e d . 65 T h e s tu d ie s o f B ar te ls e t a l. ( 20 13 ), H an k & E rl in g h ag e n ( 20 10 ) a n d P ar ki n so n ( 20 10 ) a re n o t i n cl u d e d i n t h is a n al ys is , b e c au se t h e m e an a g e a t b as e lin e i s n o t r e p o rt e d . 135747_Jacobien_Niebuur_BNW-def.indd 62 135747_Jacobien_Niebuur_BNW-def.indd 62 15-8-2020 17:27:1315-8-2020 17:27:13
