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Depression and anxiety in visually impaired older adults: cost-effectiveness of stepped
care
van der Aa, H.P.A.
2016
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citation for published version (APA)
van der Aa, H. P. A. (2016). Depression and anxiety in visually impaired older adults: cost-effectiveness of
stepped care.
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Economic evaluation of stepped care for depression and
anxiety in visually impaired older adults: multicentre
randomised controlled trial
168 169
9
Chapter 9 Economic evaluation of stepped care: RCT
Introduction
Worldwide, approximately 285 million people are visually impaired, of whom 65% are 50 years or older.1 About one third of older adults with visual impairment experience subthreshold depression
and/or anxiety (indicating subclinical symptoms), about 7% are diagnosed with an anxiety disorder, and 5 to 7% with a major depressive disorder.2 These numbers are notably higher than
prevalence estimates in the general older population.2-4 Depression and anxiety have been shown
to negatively impact vision-related disability, overall health, and quality of life, and are associated with an increased risk of mortality.4-8 In addition, depression and anxiety generate a substantial
economic burden due to increased healthcare utilisation and productivity losses.9-12
Former research has shown that psychological interventions such as self-management programmes, behavioural activation, and problem solving treatment (PST) may be effective in treating and preventing depression in older adults with visual impairment.13,14 However, evidence
is scarce, especially concerning treatment of anxiety, and long term effects are lacking. Moreover, besides a few studies on the cost-effectiveness of rehabilitation and education to increase well-being,15,16 economic evaluations on psychological interventions in the field of low vision are, to our
knowledge, not yet available.
Stepped care is a proposed model to increase efficiency in mental healthcare. In stepped care, patients receive subsequent treatment components by order of intensity, i.e. patients start with low-intensity treatments and only move on to higher-intensity treatments when a sufficient response is lacking. Progress is monitored systematically throughout the entire process. This care model is expected to lower costs by maximizing the efficiency of resource allocation, and is, therefore, recommended by Dutch and British guidelines (i.e. the National Institute for Health and Clinical Excellence).17-19 Several studies outside the field of low vision showed that stepped care is
cost-effective as compared to usual care in reducing depression and anxiety.19,20
Van der Aa et al. (2015) showed that a newly developed stepped care programme significantly reduced the incidence of major depressive and anxiety disorders with an absolute risk difference of 17%, and significantly reduced the severity of symptoms of depression and anxiety (24-months follow-up).21 However, considering the increasing number of patients with visual disabilities and
the scarce resources available for healthcare, it is important to also evaluate the cost-effectiveness of stepped care in comparison with usual care in this group of patients before implementing this intervention on a larger scale. Therefore, the aim of this study was to evaluate the cost-effectiveness of the stepped care programme in comparison with usual care in preventing major depressive, dysthymic and anxiety disorders, in reducing symptoms of depression and anxiety, and improving quality of life in older adults (aged ≥50 years) with visual impairment.
Abstract
Objectives
A newly developed stepped care intervention was found effective in preventing depressive and anxiety disorders in visually impaired older adults. However, before a decision can be made about implementation, the cost-effectiveness of this intervention in comparison with usual care should be investigated.
Methods
An economic evaluation with a follow-up of 24 months from a societal perspective was performed alongside a randomised controlled trial. Data was collected from 2012 to 2015 with telephone interviews by blind assessors. The study were performed in 17 outpatient clinics of three outpatient low vision rehabilitation organisations in Belgium and the Netherlands. From a random sample of 3000 patients, 914 patients provided written informed consent, and 265 visually impaired older adults (mean age 74, 70% women) with subthreshold depression and/or anxiety and no cognitive impairment were eligible to participate. Sixty-five percent completed all follow-up assessments. Stepped care consisted of four steps: (1) watchful waiting, (2) guided self-help based on cognitive behavioural therapy, (3) problem solving treatment and (4) referral to the general practitioner. The primary outcome was the incidence of major depressive and anxiety disorders assessed with the Mini International Neuropsychiatric Interview as described in the original protocol. Secondary outcomes were symptoms of depression and anxiety, and quality adjusted life years (QALYs) based on the EuroQol. Missing data were imputed using multiple imputation. Statistical uncertainty was estimated using bootstrapping.
Results
Based on intention-to-treat, a significant difference in the incidence of depressive and anxiety disorders (mean difference -0.17; 95% confidence interval (CI) -0.29 to -0.06) and symptoms of anxiety (mean difference -1.43, 95% CI -2.77 to -0.10) in favour of stepped care was found; no significant difference was found for symptoms of depression and QALYs. Mean intervention costs were €262 per person. Societal costs in the stepped care group were non-significantly lower as compared to the usual care group (mean difference: -€877; 95% CI: -8,039 to 5,489). Cost-effectiveness acceptability curves showed that the probability of cost-Cost-effectiveness was 77%, 88% and 95% or more at a willingness-to-pay of €10,000, €20,000 and €33,000 per disorder prevented, respectively.
Conclusions
9
the third step, patients moved to the fourth step, which was a referral to their general practitioner (GP) to discuss further treatment and the use of medication. Participants who developed an actual depressive and/or anxiety disorder as assessed with the MINI, were directly referred to their GP. Usual care included low vision rehabilitation care and/or care that was provided by other healthcare providers for both the stepped care and usual care group.Clinical outcome measures
The primary outcome was the cumulative incidence of major depressive, dysthymic and/or anxiety disorders (i.e. social phobia, panic disorder, agoraphobia, and/or generalized anxiety disorder) according to the DSM-IV, assessed at every measurement time-point with the Dutch MINI Plus (5.0.0), developed in clinician-rated format.27,28
Secondary outcomes were change in symptoms of depression and anxiety, as assessed with the CES-D and HADS-A, respectively. The CES-D contains 20 items and the HADS-A has 7 items on a four-point Likert-scale.23-26 Change in symptoms at 24 months as compared to baseline was used
in this study. This is in contrast with the previous report in which the course of symptoms was evaluated over a period of 24 months using multiple measurement time-points.21
Health-related quality of life was measured at baseline, 12 and 24 months with the EuroQol (EQ-5D-3L) which consists of five dimensions (mobility, self-care, activities of daily living, pain/ discomfort and depression/anxiety) with three answer levels (no problems, some problems, extreme problems).33 EQ-5D-3L health states were converted to health utility scores, where 0
corresponds to death and 1 corresponds to full health (range -0.33 to 1, negative utilities indicate that a health state is valued as worse than death) using the Dutch tariff.33 Quality-Adjusted
Life-Years (QALYs) were calculated by multiplying the utilities with the amount of time a patient spent in a particular health state. Transitions between health states were linearly interpolated.
Methods
Design
An economic evaluation from a societal perspective was performed alongside a two-armed multi-centre randomised controlled trial (RCT), exactly as described in the original protocol.22
The study protocol was approved by the University Hospital Leuven in Belgium and the Medical Ethics Committee of the VU University Medical Centre in Amsterdam, the Netherlands. The study was conducted according to the principles of the Declaration of Helsinki. All participants provided written informed consent. General practitioners (GP) were notified of patients’ participation in this study. Detailed information about the design of the study and the intervention is described elsewhere.21,22
Participants
From July 2012 to April 2013, a random sample of 3,000 patients aged ≥50 years from 17 outpatient clinics of three low vision rehabilitation centres in Belgium and the Netherlands were invited to participate. Of these, 30.5% (n=914) provided written informed consent, and underwent baseline interviews to determine eligibility. Patients were eligible if they: a) had subthreshold depression and/or anxiety, i.e. scored ≥16 on the Centre for Epidemiologic Studies Depression scale (CES-D)23,24
and/or ≥8 on the Hospital Anxiety and Depression Scale-Anxiety subscale (HADS-A),25,26 b) did not
meet the criteria of a major depressive, dysthymic and/or anxiety disorder according to the DSM-IV as assessed with the Mini International Neuropsychiatric Interview (MINI),27,28 c) spoke the
Dutch language adequately, and d) were not severely cognitively impaired, as assessed with the six-item screener version of the Mini-Mental State Examination (MMSE).29
Randomisation and masking
A pre-specified power calculation was based on the study of van ‘t Veer and colleagues30 who
evaluated the cost-effectiveness of stepped care in the general elderly population. They found the proportion of participants developing a disorder to be 0.2 in the intervention group and 0.4 in the control group, leading to an effect size of 2*arcsine(√0.2) − 2*arcsine (√0.4)=0.44. In addition, based on α≤0.05 (two-sided), power of 0.85, and dropout rate of 20%, a minimum of 230 patients (115 in each arm) was needed. However, since drop-out rates observed at the start of the trial were higher than expected, more patients were recruited (n=265). Participants were randomly assigned to stepped care plus usual care (n=131) or usual care only (n=134). An allocation scheme was generated by a computerized random number generator based on blocks of two and stratified by outpatient clinic. An independent researcher performed randomisation after the baseline measurement. From September 2012 to July 2015, seven telephone interview measurements (baseline, and at 3, 6, 9, 12, 18 and 24 months) were performed by trained and masked research assistants. Due to the nature of the intervention, participants and therapists could not be masked.
Intervention
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Chapter 9 Economic evaluation of stepped care: RCT
Statistical analyses
First, non-response analyses, drop-out analyses, and comparisons of baseline differences between the stepped care and usual care group were performed with χ² tests, independent samples t-tests and non-parametric tests in case of not normally distributed data. Second, a cost-effectiveness analysis and a cost-utility analysis were performed according to the intention-to-treat principle. The effectiveness analyses were previously described.21 in contrast with the effectiveness analysis,
in the cost-effectiveness analysis missing cost and effect data were replaced by using multiple imputation techniques with chained equations (MICE).38 Fifteen imputed datasets were generated,
which were analysed separately. Results from the multiple datasets were pooled using Rubin’s rules.39 Bivariate regression models were used to estimate cost and effect differences. Since costs
have a highly skewed distribution, bias-corrected and accelerated bootstrapping was applied to estimate 95% confidence intervals around the mean cost differences (5,000 replications). To calculate incremental cost-effectiveness ratios (ICERs) for the stepped care group compared with the usual care group, the difference in costs was divided by the difference in effects. Bias-corrected and accelerated bootstrapping was used to simulate the joint uncertainty surrounding the ICERs (5,000 bootstrap replications). The bootstrapped effect pairs were plotted on a cost-effectiveness plane (CE plane) for each outcome separately. The CE plane was used to generate a cost-effectiveness acceptability curve (CEAC), which shows the probability of stepped care being cost-effective in comparison with usual care for a range of different ceiling ratios (i.e. the willingness-to-pay for one additional recovered patient), thereby showing decision uncertainty.40
Statistical software packages used for analyses were SPSS for Windows version 21 (SPSS IBM, New York, USA) and Stata/SE software, version 12 (Stata Corp LP).
Sensitivity analysis
The primary analysis was based on costs from a societal perspective using the friction method to estimate indirect non-healthcare costs. In addition, two sensitivity analyses were performed: i) the cost-effectiveness analysis was performed from a healthcare perspective, thus, including only direct costs, ii) the human capital method in which every hour not worked is considered as a lost hour was used to determine productivity losses.
Results
Participant flow
Among the 3,000 invited participants, non-responders (n=2,086, 70%) were significantly older than responders (n=914, 30%, mean difference 4.6 years, P<0.001). After 24-months, 91 participants of the 265 patients who were eligible and willing to participate dropped-out (34.3%, n=45 stepped care, n=46 usual care). Those who dropped-out of the study were significantly older and more often lived in a nursing home than those who did not (P<0.05). Common reasons for drop-out were: mortality, physical or mental inability to continue, or too heavy burden. Table 2 presents baseline characteristics for both groups: education level differed significantly between groups (P<0.05).
Costs measures
Costs were collected from a societal perspective and included both direct healthcare costs (informal care was not included) and indirect non-healthcare costs (i.e. lost productivity costs). Healthcare utilisation was measured using an adapted version of the Trimbos and iMTA questionnaire for Costs associated with Psychiatric illness (TiC-P)31 and valued using standard costs from the Dutch
costing guideline (Table 1).34 Medication was valued using prices from the Royal Dutch Society for
Pharmacy. Lost productivity due to absenteeism from paid and unpaid work and presenteeism were measured using the Short Form Health and Labour Questionnaire (SF-HLQ).35 Costs of
absenteeism from paid work and presenteeism were calculated using mean age- and gender-specific income values of the Dutch population and calculated according to the friction method, which assumes that after a certain period of time (161 days) the sick employee is replaced and thus lost productivity costs are generated only during this friction period. Lost productivity costs from unpaid work were valued using a shadow price for informal care (€13.50/hour).36 Both the
TiC-P and SF-HLQ were administered at baseline, and after 6, 12, 18 and 24 months of follow-up. The costs of the stepped care programme were calculated using a bottom-up approach. The index year for the study was 2013. If necessary, consumer price indices were used to correct prices.37
TABLE 1. Unit costs to value healthcare utilisation
Cost category Unit Unit costs (2013)*
General practitioner Contact €30.64
Company physician Contact €32.26
Medical specialist Contact €78.33
Occupational or physiotherapist Contact €39.16
Social worker Contact €70.71
Psychologist or psychiatrist in private practice Contact €87.03 Psychologist or psychiatrist in hospital Contact €186.03 Mental healthcare institute worker Contact €186.03
Alternative healer Contact €44.67
Day treatment for mental care Day €167.54
Admission to regular hospital Day €473.23
Admission to academic hospital Day €625.54
Admission to psychiatric hospital Day €252.39
Admission to rehabilitation centre Day €369.89
Admission to nursing home Day €258.92
Admission to other healthcare institution† Day €497.17
Homecare Hour €38.07
Informal care Hour €13.50
9
Clinical outcomes
The cumulative incidence of major depressive, dysthymic and/or anxiety disorders after 24-months was 0.29 in the stepped care group and 0.46 in the usual care group. The absolute risk reduction was -0.17, which was statistically significant (95% confidence interval (CI) -0.29 to -0.06, Table 3). In addition, imputed and pooled outcomes showed a significant difference between the stepped care and usual care group for the HADS-A (mean difference -1.43, 95% CI -2.77 to -0.10), and a non-significant difference for the CES-D (mean difference -2.73, 95% CI -5.74 to 0.28) and QALYs (mean difference 0.03, 95% CI -0.09 to 0.15). Note that these latter analyses were different in the earlier report.21
Costs
All participants in the stepped care group received watchful waiting (n=131), 73 patients received CBT-based guided self-help (56%), PST was given to 29 patients (22%), and 7 patients were referred to the GP as part of the last step of the intervention (5%). Cost and effect data are described in Table 3. The mean total intervention costs amounted to €262 per participant. Direct healthcare costs (including intervention costs) were lower for the stepped care group, however the mean difference was not statistically significant (-€1,154; 95% CI -7,708 to 4,328). Cost savings were mainly due to significantly lower secondary mental healthcare and hospitalization costs. Indirect non-healthcare costs based on the friction method were not significantly higher for the stepped care group (€277; 95% CI -1,418 to 2,230). Total costs were lower for the stepped care group compared to usual care (-€877, 95% CI -8,039 to 5,489); this difference was also not significant.
TABLE 3. Multiply imputed pooled effects and costs (€, 2013) for the stepped care group (n=131) and usual care group (n=134) after 24 months follow-up
Outcome Stepped care
(mean (SE))
Usual care (mean (SE))
Mean difference (95% CI)*
Cumulative incidence of depressive/anxiety
disorders 0.29 (0.04) 0.46 (0.04) -0.17 (-0.29 to -0.06) Mean change CES-D score -6.40 (1.05) -3.67 (0.99) -2.73 (-5.74 to 0.28) Mean change HADS-A score -1.88 (0.47) -0.45 (0.51) -1.43 (-2.77 to -0.10) QALY 1.32 (0.04) 1.28 (0.04) 0.03 (-0.09 to 0.15) Direct healthcare
costs Medication costs 1,705 (245) 1,783 (419) -78 (-938 to 505) Primary care 10,911 (1,496) 10,124 (1,631) 787 (-3,754 to 4,910) Secondary care 3,783 (675) 5,909 (1,456) -2,126 (-5,911 to 348) Intervention costs 262 (34) 0 (0) 262 (204 to 340) Total 16,661 (1,691) 17,815 (2,680) -1,154 (-7,708 to 4,328) Indirect non healthcare costs† 5,270 (771) 4,993 (583) 277 (-1,418 to 2,230) Total costs 21,931 (2,035) 22,808 (2,956) -877 (-8,039 to 5,489) *For cost measures bootstrapped 95% confidence intervals were used
TABLE 2. Baseline patient characteristics for the stepped care group (n=131) and usual care group (n=134)
Patient characteristics measured at baseline Stepped care Usual care
Female gender (n (%)) 91 (69%) 94 (70%)
Age in years, range [50-98] (mean (SD)) 72.4 (12.5) 74.9 (11.9) Education in years, range [0-16] (mean (SD)) 10.4 (3.8) 9.3 (3.4)
Having work (n (%)) 15 (12%) 7 (5%)
Nationality (n (%)) Dutch 116 (89%) 117 (87%)
Belgian 14 (11%) 16 (12%)
Other 1 (1%) 1 (1%)
Living situation (independent) (n (%)) 115 (88%) 124 (93%)
Income (n (%)) Usually enough
money 61 (47%) 62 (46%)
Just enough money 55 (42%) 57 (43%) Not enough money 10 (8%) 15 (11%) Cause of vision loss (n (%)) Macular
degeneration 62 (47%) 60 (45%) Glaucoma 26 (20%) 19 (14%) Cataract 26 (20%) 19 (14%) Diabetic retinopathy 5 (4%) 4 (3%) Cerebral haemorrhage 5 (4%) 10 (8%) Other 45 (34%) 60 (45%)
Time of onset (years) range [0-79] (mean (SD), median) 8 [3-19] 8 [3-16] LogMAR visual acuity (n (%)) Normal visual
acuity 9 (7%) 15 (11%)
Mild vision loss 24 (18%) 23 (17%) Low vision /
blindness 86 (66%) 86 (64%)
Comorbidity range [0-5] (mean (SD)) 1.1 (1.2) 1.2 (1.2) History of major depressive disorder (n (%)) 30 (23%) 25 (19%)
History of dysthymic disorder (n (%)) 4 (3%) 1 (1%)
History of panic disorder (n (%)) 8 (6%) 8 (6%)
Baseline CES-D score (mean (SD)) 21.2 (6.4) 21.1 (6.7)
Baseline HADS-A score (mean (SD)) 7.1 (4.1) 7.1 (3.8)
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Chapter 9 Economic evaluation of stepped care: RCT
TA BL E 4 . R es ul ts o f t he c os t-eff ec tiv en es s a nd c os t-uti lit y a na ly si s b as ed o n: 1 ) a s oc ie ta l p er sp ec tiv e a nd t he f ric tio n m et ho d, 2 ) a s oc ie ta l p er sp ec tiv e an d t he h um an c ap ita l m et ho d, a nd 3 ) a h ea lth ca re p er sp ec tiv e Out come Analy sis Mean c os t diff er ence (s tepped c ar e – usual c ar e (boots tr apped 95% CI)) Mean chang e diff er ence (95% CI) ICER CE -plane NE SE SW NW Disor der So ci et al p er sp ec tiv e ( fr ic tio n) -8 77 ( -8 ,0 39 t o 5, 48 9) -0 .1 7 ( -0 .2 9 t o -0. 06 ) 5,1 59 41 % 59 % 0% 0% So ci et al p er sp ec tiv e ( hu m an c ap ita l) 20 0 ( -7 ,0 35 t o 6 ,8 29 ) -1 ,1 76 53% 47 % 0% 0% H ea lth ca re p er sp ec tiv e -1 ,1 54 ( -7 ,7 08 t o 4 ,3 28 ) 6,7 88 37 % 63% 0% 0% CE S-D So ci et al p er sp ec tiv e ( fr ic tio n) -8 77 ( -8 ,0 39 t o 5, 48 9) -2 .7 3 ( -5 .7 4 t o 0 .2 8) 321 39 % 58% 2% 1% So ci et al p er sp ec tiv e ( hu m an c ap ita l) 20 0 ( -7 ,0 35 t o 6 ,8 29 ) -7 3 51 % 46% 1% 2% H ea lth ca re p er sp ec tiv e -1 ,1 54 ( -7 ,7 08 t o 4 ,3 28 ) 42 3 35 % 62 % 2% 1% HADS -A So ci et al p er sp ec tiv e ( fr ic tio n) ) -8 77 ( -8 ,0 39 t o 5, 48 9) -1 .4 3 ( -2 .7 7 t o -0. 10 ) 61 3 40% 58% 2% 0% So ci et al p er sp ec tiv e ( hu m an c ap ita l 20 0 ( -7 ,0 35 t o 6 ,8 29 ) -1 40 52 % 46% 1% 1% H ea lth ca re p er sp ec tiv e -1 ,1 54 ( -7 ,7 08 t o 4 ,3 28 ) 807 36% 63% 1% 0% QAL Y So ci et al p er sp ec tiv e ( fr ic tio n) -8 77 ( -8 ,0 39 t o 5, 48 9) 0. 03 ( -0 .0 9 t o 0 .1 5) -2 9, 23 3 25 % 45 % 14 % 16 % So ci et al p er sp ec tiv e ( hu m an c ap ita l) 20 0 ( -7 ,0 35 t o 6 ,8 29 ) 6,6 66 7 34% 36% 11% 19 % H ea lth ca re p er sp ec tiv e -1 ,1 54 ( -7 ,7 08 t o 4 ,3 28 ) -3 8, 46 7 23% 48% 16 % 13% CI co nfi de nc e in te rv al , C ES -D Ce nt re fo r E pi de m io lo gi c St ud ie s D ep re ss io n, H AD S-A H os pi ta l A nx ie ty an d De pr es si on Sc al e-An xi et y, Q AL Y qu al ity ad ju st ed lif e ye ar , I CE R in cr em en ta l c os t-eff ec tiv en es s ra tio , C E-pl an e co st -e ffe cti ve ne ss p la ne , N E no rt h-ea st qu adr an t, SE s ou th -e as t qu adr an t, SW s ou th -w es t qu adr an t, NW n or th -w es t qu adr an t
Cost-effectiveness and cost-utility
The results of the cost-effectiveness analyses are described in Table 4. The ICER with regard to the cumulative incidence of depressive and anxiety disorders was 5,159, meaning that one prevented disorder in the stepped care group was associated with €5,159 lower costs as compared to the usual care group. The CE-plane and CEAC in Figure 1A and B indicate that for a ceiling ratio of €0 per disorder prevented the probability that stepped care was cost-effective compared to usual care was 59% (equal to the proportion of cost-effect pairs in the southern quadrants of the CE plane). At a willingness to pay of €10,000 this probability was 77%, and at a willingness to pay of €20,000 this probability was 88%. The probability of cost-effectiveness increased to 95% or more at a willingness-to-pay of €33,000 per disorder prevented. For the CES-D and HADS-A, cost-effectiveness acceptability curves show that the probability of cost-cost-effectiveness was 60% for both outcomes for a ceiling ratio of €0 per point improvement on the CES-D/HADS-A, and this probability increased to 95% or more at a willingness-to-pay of €2,500 per point improvement on the CES-D and €4,000 per point improvement on the HADS-A (Table 4).
The cost-utility analysis resulted in an ICER of -29,233 indicating that gaining one QALY in the stepped care group was associated with €29,233 lower costs as compared to usual care. The CE-plane and CEAC in Figure 1C and D show that the probability that stepped care was cost-effective compared to usual care was 59% or more for a ceiling ratio of €0 per QALY and this increased to 65% or more at a willingness-to-pay of €20,000 per QALY.
Sensitivity analysis
9
0
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Ceiling ratio: €/QALY
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-20000
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FIGURE 1A. Cost-effectiveness plane showing the percentage of major depressive and anxiety disorders prevented during 24 months follow-up in the stepped care versus the usual care group. The red dot indicates the point estimate of the incremental cost-effectiveness ratio (ICER, 17% of disorders were prevented and €877 less costs were made in the stepped care group. The grey dots indicate the bootstrapped cost-effects pairs reflecting the uncertainty surrounding the ICER
FIGURE 1C. Cost-effectiveness plane showing the change in quality adjusted life years (QALY) during 24 months follow-up in the stepped care versus the usual care group. The red dot indicates the point estimate of the ICER, mean difference was 0.03 and €877 less costs were made in the stepped care group. The grey dots indicate the bootstrapped cost-effects pairs reflecting the uncertainty surrounding the ICER
0
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Ceiling ratio: €/disorder prevented
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180 181
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Chapter 9 Economic evaluation of stepped care: RCT
(6 months) may have introduced recall bias, especially since the study population concerned an elderly population. Third, our outcomes can only be generalized to visually impaired older adults that were registered at a low vision rehabilitation organisation. Visually impaired people that do not seek help from these organisations may be less engaged in following the intervention. Moreo-ver, people who were eligible and volunteered to participate in this study were younger and may have been relatively healthier (i.e. not cognitively impaired and able to participate in this study).
Implications for practice and directions for future research
This study shows that stepped care is a promising intervention in the psychological treatment of mental health problems in visually impaired older adults. Stepped care enables professionals to efficiently deploy their limited resources by offering low intensity and low costs interventions and only move on to higher intensity interventions when sufficient response is lacking. The stepped care programme is effective in preventing major depressive and anxiety disorders as compared to usual care, and the probability that stepped care is cost-effective compared to usual care is 95% or more at a willingness-to-pay of €33,000 per disorder prevented. Decision makers need to decide whether this is an acceptable amount of money for society to pay. Future studies should investigate how the cost-effectiveness of the stepped care intervention in comparison with usual care can be improved. Options that could be explored are: offering interventions tailored to the needs of patients and severity of depression and anxiety symptoms, e.g. the period of watchful waiting may vary based on personal needs and symptom severity,42 and some patients may
benefit from directly offering higher intensity interventions or medication, i.e. visually impaired persons with a history of depressive and/or anxiety disorder.21 In addition, other evidence-based
treatment options (e.g. exercise programmes) and e-mental health interventions could be added to the model. E-mental health, specifically developed for visually impaired older adults, using the increasing possibilities of assistive technology may decrease intervention costs by replacing face-to-face contact by online sessions. In summary, this study shows that effective and cost-effective treatment of depression and anxiety in older adults with visual impairment should be possible. Further research may indicate whether these results are maintained when implementing this intervention in routine care.
Discussion
This economic evaluation shows that the stepped care programme is clinically superior to usual care, and is associated with modest (non-significant) cost savings as compared to usual care. Cost savings are mainly due to lower secondary mental healthcare costs and lower costs for hospitalization in people who receive stepped care compared with those receiving usual care. Mean intervention costs are low (€262), which is comparable to other stepped care programmes.20,41
Cost-effectiveness acceptability curves show that the probability that the intervention is cost-effectiveness compared to usual care is 77%, 88% and 95% or more when society is willing to pay €10,000, €20,000 and €33,000 per disorder prevented, respectively. Decision makers need to decide whether these probabilities with corresponding amounts of money for society to pay are acceptable to prevent one anxiety or depressive disorder in older adults with visual impairment. Lost productivity costs were higher for stepped care compared to usual care. However, since only a small number of participants (8% of the total study population) had a paid job in this older population, the analysis was also performed from a healthcare perspective (including only direct healthcare costs), showing slightly more positive outcomes. Based on this perspective there is a 63% probability of stepped care being cost-effective compared to usual care when society would not be willing to pay anything to prevent a depressive or anxiety disorder in visually impaired older adults, and this probability increases to 95% or more at a willingness to pay of €26,000 per disorder prevented. Although lower than in the main analysis, decision makers need to decide whether this is acceptable.
Although the stepped care intervention was significantly more effective in preventing depressive and anxiety disorders in comparison with usual care, the difference in QALYs, in favour of stepped care, was not statistically significant. This may be explained by the nature of the outcomes. QALY is a measure of health-related quality of life, including diverse dimensions (i.e. mobility, self-care, activities of daily living, pain/discomfort and depression/anxiety), of which mental health is covered in only one dimension. Since the stepped care intervention was specifically aimed at improving mental health, it cannot be expected that the intervention results in similar improvements in quality of life. When looking at the dimensions separately, we see that stepped care significantly reduced problems with activities of daily living and depression and anxiety compared with usual care, however, no significant difference was found on the other dimensions.
Strengths and limitations
This study is to the best of our knowledge the first to evaluate the cost-effectiveness of a stepped care intervention in a population of older adults with visual impairment. Previous studies in the field of low vision were mostly limited to investigating the effectiveness of psychological inter-ventions. However, additionally performing an economic evaluation is highly relevant in a field in which patient numbers are vastly increasing and healthcare systems have difficulty addressing treatment demands. Providing information on the cost-effectiveness of treatments can help pol-icy makers make evidence-based decisions on whether implementation of the intervention can be considered an efficient allocation of scarce resources. A long follow-up period was chosen to assess long term treatment effects. In addition, a pragmatic design was chosen to inform policy makers on the cost-effectiveness of treatments in real-life situations and to increase the general-isability of the results.
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