Outcomes after Spinal Cord Injury
Osterthun, Rutger
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7
General discussion
1. maIN fINdINgS
This thesis provided insight into outcomes and their determinants of persons with SCI at the level of survival and functioning in the hospital, rehabilitation and post rehabilita-tion phase. The main findings of this thesis, according to phase and outcome were as follows.
Hospital phase, survival (chapter 2)
In 2010, 30 of the 159 patients with new traumatic SCI died during their initial hospital stay in the Netherlands. Deceased patients were considerably older and had more comorbidities than patients who survived. Furthermore, their injuries were more fre-quently high cervical and motor complete. End-of life decisions (ELDs) were reported in the majority of deaths (19/30, 63.3%) and all consisted of non-treatment decisions. There were no cases of euthanasia or physician-assisted suicide.
Rehabilitation phase, functional outcome (chapter 3)
Persons with non-traumatic SCI formed a majority in the Dutch and Flemish SCI population between 2002 and 2007, and showed a more even gender distribution, a more advanced age and less severe lesion characteristics than the group of persons with traumatic SCI. Aetiology was a weak independent determinant of LOS, but was not an independent determinant of functional outcome of the inpatient rehabilitation. Age, injury characteristics and the functional status on admission were independent predictors of functional outcome.
Rehabilitation and post rehabilitation phase, survival (chapter 4)
A high number of persons with traumatic and non-traumatic SCI who had survived the acute hospital phase died during the 6.2 year follow up (12%, standardized mortal-ity ratio (SMR) 5.3) in a cohort of wheelchair dependent persons with SCI, aged less than 65 years. Cardiovascular and pulmonary diseases were the major causes of death (65%). Persons with non-traumatic SCI, with a higher age at injury and a history of other medical conditions had a higher risk of dying in the first few years after injury.
Post rehabilitation phase, functional outcome (chapter 5 and 6)
In a cross-sectional study in persons with long-standing SCI we found no differences in functional independence measured with the SCIM III between strata of time since injury (TSI) (10-19, 20-29, 30+ years) in persons under 65 years of age with a motor complete SCI in the Netherlands. The level of injury was the strongest determinant, and TSI nor age were associated with long-term functioning. Waist circumference was
another weak, but independent determinant. Aetiology was not a determinant of long-term functioning.
In a cross-sectional study in persons with long-standing SCI we found that a higher POpeak was related to better participation levels in persons with a long-standing SCI after controlling for relevant confounders. Functional independence was the only confounder.
The findings of this thesis add information to existing literature on survival and func-tioning after SCI. The results also contribute to describing and understanding epide-miological trends within the field of SCI. Three epideepide-miological trends are addressed in the introduction of this thesis. Since these trends have a considerable impact on the characteristics of the SCI population, and consequently on determinants of outcomes, the interpretation of the results of this thesis will be further discussed in three themes according to changing characteristics of the SCI population (sections 2-4). These themes are respectively 1) increasing number of persons with non-traumatic SCI, 2) chang-ing personal and injury characteristics of persons with new SCI, and 3) an increaschang-ing number of persons aging with SCI.
Each section starts with a paragraph on the theme in general and the contribution of our results to the theme. The subsequent paragraphs of the section describe important aspects of our results on outcomes in relation to these themes.
2 NON-TRaumaTIC SCI
2.1 Increasing number of persons with non-traumatic SCI
The results of chapter 3 showed that the majority (54.7%) of persons with SCI admitted to rehabilitation centres in the Netherlands and Flanders had a non-traumatic SCI. As there are no incidence figures of persons with non-traumatic SCI in the Netherlands, the finding of chapter 3 gives a useful indication of the high proportion of non-traumatic aetiology of SCI in the Netherlands. The finding is in line with more recently described incidence rates of non-traumatic SCI in developed countries, which were also found to be higher than that of traumatic SCI.1,2
Two comments can be made regarding these findings. First, the registry used in chapter
3 was not population-based and did only include persons admitted to SCI specialized
rehabilitation centres for first inpatient rehabilitation. These centres may admit more severely injured and more younger patients than nursing homes.3 Further, the study
population of chapter 3 also included persons with tumors. It is however suspected that the majority of persons with (malignant) tumors is not referred to a rehabilitation centre in the Netherlands, as there may be a unfavorable overall prognosis and a risk of
neurological deterioration.4 However, reliable data on the incidence of tumor related
SCI is sparse and the proportion of tumor related non-traumatic SCI in rehabilitation centres in chapter 3 (28%) is more or less in line with other studies (20.1-36.4%).5-12
An increase of the proportion of non-traumatic SCI in rehabilitation centres in the Netherlands can be observed when comparing the results of chapter 3 (54.7%) with the results of a single-centre study performed in 1982-1993 (52%)13 and a study in
2015 (65.5%).14 It has been estimated that about half of the cases of non-traumatic
SCI are age related.9 As a result of aging of the general population it is expected that
the incidence of non-traumatic SCI will increase dramatically.1 So far, most research
is performed with persons with traumatic SCI.15 Considering the anticipated growth
of the non-traumatic SCI population, insight into characteristics and outcomes of this population remains important for health care planning.
2.2 Comparing non-traumatic with traumatic SCI
We showed in chapter 3 that the characteristics of persons with non-traumatic SCI differed from those of persons with traumatic SCI. Persons with non-traumatic were older, had more frequently a paraplegia and an incomplete SCI than persons with traumatic SCI. Furthermore, their gender distribution was more even. These differences are in agreement with results from other studies.5-7,11,13 A more recent population based
study in Australia confirmed the differences regarding to age, level of injury and gender distribution. The completeness of the injury was not assessed in that study.16
Although persons with non-traumatic SCI form a substantial part of the SCI population and the characteristics of non-traumatic SCI differ from traumatic SCI, few studies are performed comparing outcomes between these groups. Results of this thesis showed that non-traumatic origin of SCI was an independent determinant of mortality (chapter
4), indicating this group is more vulnerable for premature death. This result is more
recently confirmed in another study.17 The results of chapter 3 showed that persons with
non-traumatic SCI seem to benefit to more or less equally from inpatient rehabilitation as persons with traumatic SCI.10,18,19 However, there were clear differences in the
degree of functional change during rehabilitation, functional status on admission and at discharge, and functional gain per day of admission. Other studies found more or less similar results on this subject. As shown in chapter 3, persons with non-traumatic SCI had a higher functional status on admission,10,18,20,21 shorter length of stay,10,18,20,21
and higher functional status at discharge.21 Persons with traumatic SCI gained more
functional improvement during inpatient rehabilitation,18,21 but the functional gain for
each day of admissions was higher for persons with non-traumatic SCI.21 Studies have
also described a more or less similar functional status at discharge10,20 and slightly
more favourable outcomes for persons with traumatic SCI.18 This last study found a
Non-traumatic SCI was, however, not an independent determinant of functional outcome of rehabilitation (chapter 3) and also not a determinant of long-term functional independence (chapter 5). The study of chapter 3 was the first study to evaluate independent influence of aetiology (traumatic versus non-traumatic). A more recent study confirmed the result that aetiology was not an independent determinant of functional outcomes of the rehabilitation.19 The use of a self-developed scale of
functioning in chapter 3 may be considered a limitation of these findings. However, the measure was based on the well-known Functional Independence Measure and showed an excellent internal consistency.
The results on functional outcomes after SCI underpin the importance of offering persons with non-traumatic SCI rehabilitation in SCI specialized services.20 It has
been suggested that the needs of both non-traumatic SCI and traumatic SCI can be targeted with the same rehabilitation program,20 although several areas of concern for
rehabilitation of persons with non-traumatic SCI have been addressed, for example, the uncertain, variable, and possibly even gradually deteriorating neurological prognosis.22
Also the vulnerability of persons with non-traumatic SCI, when it comes to survival, should be an area of concern.
3. ChaRaCTERISTICS Of PERSONS WITh NEW SCI
3.1 Increasing age at injury
Mainly as a result of aging of the general population, the age at injury of persons with new traumatic and non-traumatic SCI has considerably increased. Non-traumatic SCI is found to be associated with increasing age.1,2,23 Concerning traumatic SCI, a study on
the incidence of traumatic SCI in the Netherlands in 2010 showed that the age at injury of persons with a new traumatic SCI has increased in the past decades. Traumatic SCI is now most commonly seen in persons older than 60 in that study.24
Concerning admissions to rehabilitation centres, chapter 3 showed that almost 47% of persons with non-traumatic and 18% of persons with traumatic SCI in the Netherlands and Flanders between 2002 and 2007 were aged 60+. Mean ages for traumatic and non-traumatic SCI were 43 and 57 years, respectively. A more recent study on the profile of patients admitted to rehabilitation centres in 2015 showed that the mean ages for persons with traumatic and non-traumatic SCI were respectively 52 and 59 years.4
As a result of further aging of the general population, it is likely that the group of persons aged 60+ with new (traumatic and non-traumatic) SCI will further increase in the future. It seems reasonable to assume that elderly with new SCI will form the
largest group of persons with SCI and will form a substantial part of admissions to rehabilitation centres in the Netherlands.
3.2 Increasing number of incomplete injuries
The large proportion of older persons with a new SCI also causes changes in the profile of injury characteristics. Non-traumatic SCI usually results in an incomplete paraplegia (chapter 3), while a traumatic SCI in elderly usually results in an incomplete tetraplegia.24 With an increasing age at injury there will thus be an increasing number
of persons with incomplete injuries.
3.3 Effect of increasing age and increasing number of incomplete injuries
on outcomes
A higher mean age at injury may affect mortality figures. Age at injury has been shown to be a determinant of in-hospital mortality in traumatic SCI (chapter 2) and an independent determinant of mortality in a cohort with persons with traumatic and non-traumatic SCI who had survived the hospital phase (chapter 4). This applied to the participants of chapter 4 even when persons older than 65 and persons with malignant tumor as cause of the SCI were excluded. Age as determinant of mortality is in line with other literature.25 Besides age, the results of chapter 4 showed that a non-traumatic
cause of the SCI and the presence of comorbidities were also independent determi-nants of death. This common combination of determidetermi-nants may thus lead to a higher mortality.
Another, underexposed, mortality-related issue that seems to be related to a higher age at injury is the application of ELDs. Chapter 2 showed that ELDs played a prominent role in in-hospital mortality in the Netherlands and this mortality was strongly age-related. There is no historical data on ELDs after traumatic SCI. In patients admitted to an intensive care unit, age is found to be an independent determinant of withholding or withdrawing treatment.26 Based on increasing numbers of elderly with new traumatic
SCI, the proportion of in-hospital ELDs may increase in the future.
An increasing age at injury and a concomitant change in predominant injury characteristics towards more incomplete injuries may have important consequences regarding rehabilitation facilities, health care planning and rehabilitation outcomes. Age at injury and completeness of the injury were found to be independent determinants of functional rehabilitation outcomes (chapter 3). The influence of age on functional outcomes may be based on a reduced ability to recover and the effect of comorbidities. A similar picture is outlined in other literature. Older persons seem to benefit from rehabilitation, although less pronounced than their younger counterparts.10,27,28 In a
study in persons with a tetraplegia, older persons showed less functional improvement than younger persons and they needed more time to reach these outcomes.27 In a study
on persons aged 65+ with SCI, a higher age at injury (≥50 years) was associated with lower participation and life satisfaction scores, compared to persons with a lower age at injury (<50 years).29 Adjusting rehabilitation programs to the needs and pace of persons
with a higher age at injury may improve outcomes for this group.
The increasing number of incomplete injuries may affect rehabilitation outcomes. Functional outcomes of rehabilitation will in general be better, as shown in chapter 3. Furthermore, the number of persons with the potential to walk will increase. Finally, functional prognoses of these injuries may be less straight forward when comparing to complete injuries.
4. agINg WITh SCI
4.1 Increasing number of persons aging with SCI
As noted in chapter 1 and chapter 4, survival after SCI has considerably improved since the 1950s.25,30 In some studies, a distinction is made between survival in the first year
after injury and long-term survival (beyond the first year).31-33 Especially studies from the
U.S. have shown that the long-term survival, in contrast to the one year survival, has not improved since the 1980s.31,32,34 In other words, although more people are now aging
with their SCI, life expectancy does not seem to have improved in the past decades. In chapter 4, a selected cohort of persons with SCI in the Netherlands was followed from admission to rehabilitation up to 6 years after the injury. During this period a notable number of 27 out of 222 persons died (12.2%). The found Standardized Mortality Ratio (SMR) of 5.3, indicating that more than 5 times more persons with SCI died than their peers without SCI, is on the high end of SMRs found in recent literature (1.5-5).30 As the examined cohort in chapter 4 was small, no firm conclusions can be
drawn from this SMR.
The top 3 causes of death in chapter 4 resemble those of the general population, which fits into a trend that is found in other literature.25 Nevertheless, people with SCI
still die from SCI specific causes of death, such as pulmonary embolism or pulmonary complications. Striking in this context were three young persons with SCI who died within one year from onset of SCI due to pulmonary embolism (chapter 4).
The predominance of causes of death after SCI that are also found in the general population, in combination with a high mortality ratio, suggest that an accelerated aging process in persons with SCI may play an important role in premature deaths. In persons aging with SCI, it is shown that the deterioration of the cardiovascular system is accelerated as result of a sedentary lifestyle. Other body systems, such as endocrine, immune, respiratory and musculoskeletal systems are also found to age prematurely
in persons with SCI35 and persons aging with SCI are found to be more susceptible for
developing SHCs.36-38
4.2 healthy aging
Most attention in research on SCI is paid to the (sub)acute phase. Since more people are now aging with their SCI, attention is increasingly being paid to healthy aging. Healthy aging is defined by the World Health Organization as the process of developing and maintaining the functional ability that enables wellbeing in older age.39 Healthy aging
and maintaining life satisfaction are subjects that apply to all aging persons, but have become increasingly important after SCI.40,41
To “maintain the functional ability that enables wellbeing in older age” is related to functioning in terms of the International Classification of Functioning, Disability and Health (ICF). Quality of life after SCI is shown to be dependent of participation, more than performing activities.42 Conform the ICF model, participation is related to
performing activities and personal and environmental factors.43,44 Considering healthy
aging, maintaining functional levels may be an important issue for persons aging with SCI. Concerning quality of life of persons aging with SCI, some decline on specific domains has been described. However, this seems to be in line with persons aging in the general population.45 Further, a review on quality of life in persons aging with SCI
showed that persons seem to be able to maintain their experienced quality of life.45
This may be partly explained by the ability to adapt to a new situation46 and the “life
span development” theory. The life span development theory is about the actual timing of an event in relation to the expected occurrence. Events that are expected to happen with aging seem to be less problematic than events that are not expected with aging.47
4.3 functional outcomes of persons aging with SCI
Aging after SCI is thought to have impact on functional outcomes.45,48 In chapter 5
functional independence of persons with long-standing motor complete SCI aged <65 was analyzed, grouped by time since injury (TSI) strata (10-19, 20-29, 30+ years). The encouraging result was found that persons in the three TSI strata functioned on a similar functional independence level based on the Spinal Cord Independence Measure III (SCIM III). In this study, age nor TSI were a determinant of long-term functioning. Due to the cross-sectional design, no conclusions can however be drawn on the true effects of aging. Some comments can be further made regarding these findings. First, the survivor effect, meaning that healthier subjects may have been more available or willing to participate, may have biased the results. Second, the SCIM III may not be sensitive enough to detect functional changes in an aging population. Finally, generalization of the results of this study is limited by the inclusion criteria. As a result of the age criteria, the persons included in the study may have not been old enough to detect changes in
functioning. Nevertheless, the results of chapter 5 suggest that wheel-chair dependent persons with SCI aged less than 65 are able to maintain their functional abilities for a long period.
Besides functional independence, participation levels of persons SCI may decrease with aging.49 A recent cross-sectional study on the same population of chapter 5 and
6 showed only a decrease in participation levels on some aspects of participation.50
4.4 The relation between body functions and functional outcomes of
persons aging with SCI
The injury characteristics are well known determinants of functioning.51 Chapter 5
showed that level of injury was the strongest independent determinant of functional independence in persons with long-standing motor complete SCI. To date, injury char-acteristics of persons with long-standing motor complete SCI are not modifiable. Other body function related determinants of outcomes in persons aging with SCI are the waist circumference and the physical capacity (chapter 5 and 6). Although weakly related, a higher waist circumference was found to be associated with lower long-term functional independence (chapter 5). This seems to confirm results of a study that found a relation between body composition and long-term mobility.52 Since waist circumference seems
to be related to a healthy lifestyle, this finding supports the importance of a healthy lifestyle.
Chapter 6 focused on the relation between physical capacity and participation in
persons with long-standing SCI. In this study, a good physical capacity (higher POpeak) was related to better participation levels after controlling for functional independence, which turned out to be the only confounder. A good physical capacity seems to be a key issue in healthy aging, as it is also found to be related to better health, performing activities and quality of life.53-56 Another study found that an increasing number of SHCs
and a need to save energy influenced participation in activities, especially exercise and social activities.57 Combining this with the results of chapter 6, a decreasing physical
capacity may thus lead to a downward spiral in functioning.
5. ClINICal ImPlICaTIONS
5.1 hospital phase
The results of this thesis show the importance of having care providers in the hospital phase with knowledge of long-term consequences of SCI. This is supported by two findings. First, aetiology (traumatic versus non-traumatic) was not a determinant of functional outcome in the rehabilitation phase, and also not a determinant of long-term functional independence. It is thus important that persons with non-traumatic
SCI are recognized as such in the hospital, that they receive realistic information on future perspectives and that they are referred to appropriate rehabilitation facilities, if applicable. Second, the substantial proportion of ELDs in in-hospital mortality also shows the importance of giving persons with SCI appropriate and realistic information on future perspectives. To facilitate this process, a standardization of the procedure of ELDs is advised.
5.2 Rehabilitation phase and post rehabilitation phase
Although life expectancy has considerably improved, there remains a higher risk of premature death in persons with SCI. Persons with non-traumatic SCI, with a higher age at injury and a history of other medical conditions have a higher risk of dying in the first few years after injury. Also since cardiovascular deterioration seems to play an important role in premature deaths, discussing the importance of a healthy lifestyle with patients in this group should start early and be a routine part of regular follow up after discharge of rehabilitation.
In the past years increasing attention is paid to healthy aging after SCI. Maintaining health and the physical capacity seem to be key issues in healthy aging, which can be defined as creating the environments and opportunities that enable people to be and do what they value throughout their lives.
Besides the known benefits of a good physical capacity on healthy aging, a good physical capacity in persons with long-standing SCI was related to better participation levels. Especially since persons with a SCI tend to have an inactive lifestyle, paying attention to the importance of a healthy lifestyle during rehabilitation and afterwards is important as it may improve or maintain functional levels and quality of life. Aspects that facilitate healthy aging, such as improving or maintaining the physical capacity, should be a central theme during follow-up.
6. CONSIdERaTIONS fOR fuTuRE RESEaRCh
As a result of ongoing developments in health care and demographic changes of the general population, further studies on outcomes on the level of survival and functioning after SCI are important to preserve insight into developments in the SCI population. Insight into outcomes and their determinants is essential to improve health care and ultimately outcomes after SCI. Standardized registration of information of personal and injury characteristics, survival and functional outcomes should be a basis for further research. Since SCI is a rare condition, multicenter research and international collabo-ration is important to catalyze knowledge of SCI. Further, collabocollabo-ration with patient associations is essential to be able to meet the needs of persons with SCI.
An underexposed aspect on mortality after SCI is the application of ELDs. It would be relevant to include information on ELDs in future studies on in-hospital mortality. Larger, prospective studies focusing on ELDs in more detail can further contribute to the understanding of the application of ELDs. More specifically, information on the types of ELDs, characteristics of the involved patients, considerations, the timing, the capability of the patients to make an informed decision and the content of the information provided to the patient and family would be valuable. Gaining insight into the application of ELDs across countries may lead a better understanding of mortality figures and ultimately also to a better substantiation of decisions.
Three themes on changing epidemiological characteristics are described in the discussion of this thesis. Changing epidemiological characteristics demand for different accents in research.
Firstly, although persons with non-traumatic SCI form the majority of the SCI population, most research is being conducted with persons with traumatic SCI. There is especially more need for knowledge how to improve outcomes in different subgroups of non-traumatic SCI. More basic information on survival and functional outcomes is needed to be able to adjust therapy to the individual’s needs. This seems especially necessary for persons with SCI due to a malignant tumor.58
Secondly, as a result of an increasing number of persons aged 60+ with new SCI, more insight is needed into the needs of this subgroup. Especially, more insight into the needs of this group is needed to optimize quality of life and participation levels. Further, insight into the pace of rehabilitation that is needed to optimize outcomes for this group would be valuable.
More research is needed on persons with incomplete injuries. Since there will be an increasing number of persons who are potentially able to walk, insight into physical behavior and experienced strain of persons who are able to walk is essential for determining interventions to improve walking and healthy behavior. Further, exploring interventions to improve walking seems necessary with the changing demographics.
To date, most research on outcomes after SCI is conducted in the (sub)acute phase. Little is still known on (healthy) aging after SCI. Since life expectancy does not seem to have improved since the 1980s, more research is needed on healthy aging. For example, the role of deterioration of certain body systems should be further cleared in relation to survival. Further, interventions should target on maintaining health and preserving the physical capacity, as a foundation for healthy aging.
Longitudinal studies with a lifelong follow-up seem necessary to further unravel determinants of healthy aging. The most effective way to gather relevant information seems to be a standardized registration of information on survival, ELDs, personal factors, injury factors, health parameters, the occurrence of secondary health conditions, functional outcomes and quality of life. This registration should preferably
yield information that is easy to retrieve from the Electronic Patient Files (EPF) and that is relevant for both research and clinical purposes. The EPF should preferably be pre-structured for persons with SCI. In the Netherlands, the current registry, performed with the Dutch Dataset for SCI for inpatient rehabilitation, could be extended to regular follow-up moments after inpatient rehabilitation. Large databases should provide data for comparison across institutions and countries. Information gathered with such longitudinal research should be an important foundation for identifying intervention strategies to improve outcomes, and thus for healthy aging.
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