Aging is a complex process that does not only encompass biology. Environmental factors also change over time, which may be particularly important to persons with SCI, because they not only face physical limitations associated with their SCI, but also injury-related social and economic changes (Krause & Coker 2006). For example, in a series of papers reporting on the same cohort at different time points over a period of 30 years, there were significant improvements with satisfaction with employment and finances over time (Crewe & Krause 1990; Krause 1992; Krause 1998; Krause & Broderick 2005; Krause & Coker 2006), whereas satisfaction with both social and sexual relationships decreased (Krause 1997; Krause & Broderick 2005; Krause & Coker 2006). Similarly, Bushnik & Charlifue (2005) observed changes related to economics and technology, but not related to SCI or aging per se. For example, letter writing, which probably included emails, increased in the sample over time because home computing had likely become more common. Although not significant, the high percentage of persons who switched to a portable ventilator or pneumobelt from a fixed ventilator may have improved community reintegration for these individuals. As well, the finding that economic self-sufficiency steadily improved with time (e.g. Charlifue & Gerhart 2004a; Krause & Broderick 2005; Krause & Coker 2006) supports Bushnik’s (2002) speculation that increased economic standing may improve community reintegration. In the case of Bushnik’s (2002) sample, improved financial status enabled better access to adaptive equipment (e.g. modified vans).
Conversely, level of community reintegration for Charlifue & Gerhart’s (2004a) sample did not significantly change over time, but this may have been due to sample differences between the studies and that the time between data collection intervals in the other studies reviewed were further apart. As well, the individuals in Charlifue and Gerhart’s (2004a) study were at least 20 years post-injury when they entered the study. At 20 years post-injury, it is likely that routines and strategies for community participation have been well-established, and are not likely to dramatically change over 3 year periods. However, an understanding of environmental factors is important for assessing QoL since there is evidence that an individual’s adjustment over time is influenced by corresponding environmental changes (Krause & Sternberg 1997).
With regards to change in activity patterns, Bushnik and Charlifue (2005) attributed the changes to the natural progression of time utilization from external social activities associated with youth (e.g. card games with friends) to other activities (e.g. spending time with family). Further, the reported declines in activity by the SCI cohorts as they aged (e.g., Bushnik 2002, Charlifue and Gerhart 2004a, and Krause & Broderick 2005) might be similar to declines in activity patterns in the general population (Christensen et al. 1996; Bukov et al. 2002).
One of the main strengths of the studies by Krause (1997), Krause and Broderick (2005), and Krause and Coker (2006) is they assessed whether there were any differences between their current sample and those who were lost to follow-up. Based on these analyses, clear survivor effects emerged in both studies as the characteristics of respondents (persons who participated in both data collection periods) at Time 1 were younger, younger at age of SCI-onset, were less years post-injury, had higher levels of education, more likely to have cervical injuries, greater sitting tolerance, and had more social outings than non-respondents (persons who only participated in the first data collection period). These findings highlight that some care should be taken when interpreting the findings from these studies as it may only reflect survivors, and those who continued to participate.
The findings appear to provide some mixed evidence regarding the stability of QoL/life satisfaction over time. In some cases QoL/life satisfaction remained stable (i.e., Charlifue et al. 1998; Charlifue et al. 1999; Charlifue & Gerhart 2004b; Savic et al. 2010; Pershouse et al. 2012), or decreased over time (i.e., Krause 1997; Charlifue et al. 1998). Similarly, Mitchell & Adkins 2010 that aging has greater negative influence on self-rated health in people with SCI than on those without a SCI over time. In other studies QOL/ life satisfaction improved with over (Stensman 1994; Kemp & Krause 1999; Bushnik 2002; Putzke et al. 2002b; Bushnik & Charlifue 2005; Krause & Coker 2006; van Koppenhagen et al. 2009; DeVivo & Chen 2011; Kalpakjian et al. 2011; van Leeuwen et al. 2011). Likewise, mental health has also been reported to improve longitudinally (van Leeuwen et al. 2012).
The discrepancies in these studies may potentially be attributed to theoretical and methodological differences. For instance, the study by Charlifue et al. (1998) was the only study that explicitly provided a theoretical model for assessing life satisfaction. Specifically, Charlifue and colleagues (1998) framed aging with SCI within a global thesis of function, which took into account physical, psychological, and environmental factors. Several studies with lower levels of evidence predicting life satisfaction have used other models that incorporate a variety of domains thought to impact on QoL (i.e., Pierce et al. 1999; Richards et al. 1999; Tonack et al. 2008). Unfortunately, Charlifue et al. (1998) did not provide a clear rationale for including specific predictor variables in their models. A larger theoretical concern is the issue of response shift (also known as recalibration, reprioritization, and reconceptualization; Schwartz & Spangers 2000), which refers to a dynamic process where an individual undergoes simultaneous changes in their internal standards, values, and conceptualizations of QoL in response to health and physical functioning changes (Tate et al. 2002). Ambiguous or paradoxical findings can occur because of differences among people or changes within people regarding internal standards, values, or conceptualization of health-related QoL (Schwartz et al. 2007). As a result, the psychometric properties (e.g., validity and reliability) of measurement tools can be affected (Schwartz et al. 2007).
In terms of methodological differences, because the samples in each of the studies had different mean ages and YPI it is not surprising that there are discrepancies in reported QoL. However, when examining the QoL results by an aging parameter, YPI for example, a common finding was that regardless of age, individuals with relatively new SCI (i.e.≤5 YPI) are more likely to experience improvements to their QoL (Stensman 1994; Kemp & Krause 1999; Bushnik 2002; Putzke et al. 2002b; Bushnik & Charlifue 2005; Krause & Coker 2006; van Koppenhagen et al. 2009; DeVivo & Chen 2011; Kalpakjian et al. 2011; van Leeuwen et al. 2011) than individuals with longer term SCI (i.e., ≥6 YPI) who consistently report high and stable QoL levels (i.e., Charlifue et al. 1998; Charlifue et al. 1999; Charlifue & Gerhart 2004b; Savic et al. 2010). That is, after sustaining a traumatic SCI, the QoL of these individuals may be low and have more room to improve than those individuals with longer term SCI. In fact, Dijkers (2005) noted that the wellbeing after SCI reaches a plateau at the end of the adjustment period, which is estimated to last from two to five years (Dijkers 2005). Similarly, Whalley-Hammell (2007) reported that after a four year adjustment period, individuals with SCI feel as though as they live a normal life, and have the same problems as everyone else (Whalley-Hammell 2007). In this review, there one study however that observed no changes in QoL among individuals with ≤5 YPI (Mortenson et al. 2010). Mortenson et al. (2010) argued that the individuals may have already adjusted and experienced a response shift prior to the baseline assessment.
Although age of SCI onset does not appear to limit the potential high QoL, there are likely age-related factors that may potentially influence QoL. For example, in studies with samples with mean ages in the 20s, individuals were found to have greater improvements in life satisfaction and QoL if they were students, lived independently, had a lower level injury, had overcome past medical problems, and if they had accessible vans for transportation (Barker et al. 2009; Sakakibara et al. 2012). Among individuals in their 30s, both Putzke et al. (2002b) and Stensman (1994) found QoL to be influenced by amount of pain and interference with pain (Putzke et al. 2002b; Stensman 1994),and Kalpakjian et al. (2011) found the relationship between life satisfaction and YPI to vary depending on marital status and gender (Kalpakjian et al. 2011).
Furthermore, the nature of the control group can lead to different interpretations of the results. A strength of Kemp and Krause‟s (1999) was the use of an able-bodied, and a control group with disability (i.e., polio) when examining issues of QoL after SCI as it provides some context to the extent of some problems for persons post-SCI (i.e. levels of depression). However, the characteristics of the control groups were significantly different to the group with SCI on some key factors. For instance, the able-bodied and polio groups were significantly older (p< 0.01) and had higher levels of education than the group with SCI (p< 0.05). As well, the polio group was comprised mostly of females, had a mean pediatric age of onset, was 50.9 years post-polio, and 90% were Caucasian, whereas the SCI group was comprised of mostly males from culturally diverse backgrounds, and who had an adult age of onset, and were only 14.5 years post-injury. This limitation was addressed in the study, but highlights that the findings should be interpreted with caution since many socio-demographic and historical factors may have influenced levels of depression and life satisfaction. Nonetheless, the finding that persons with SCI have lower QoL compared to the able-bodied population is consistent with other studies that did not meet the SCIRE inclusion criteria (Kemp & Ettelson 2001).
Finally, although a couple of studies reported declines in QoL over time (Krause 1997; Charlifue et al. 1998), subsequent papers focusing on the same cohorts at longer lengths of follow-up reported different results. For example, Charlifue et al. (1998) first reported that after 3 years of observation 76% of the sample consistently rated their overall QoL as either good or excellent, but that there were significant decreases in life satisfaction, as measured by the life satisfaction index (LSI), among older individuals, those with <30 YPI and >40 YPI, and those with complete paraplegia (Charlifue et al. 1998). At a follow up thirteen years later, Savic et al. (2010) similarly reported that 76% of the sample consistently reported overall QoL as good or excellent, with the highest life satisfaction reported at the last time point (Savic et al. 2010). Similarly, over two time points 9 years apart, Krause (1997) reported diminished satisfaction related to social and sex lives, as measured by the life situation questionnaire (LSQ)* (Krause 1997). Lower satisfaction is corroborated in papers by Krause and Broderick (2005) and Krause and Coker (2006) which used observations from the same cohort at different lengths of follow-up (Krause & Broderick 2005; Krause & Coker 2006). However, these two papers in addition to Crewe and Krause (1990), Krause (1992), and Krause (1998), all reported significant increases in satisfaction related to employment among the same cohort over various lengths of time (Crewe & Krause 1990; Krause 1992; Krause 1998). In general, the overall and common finding from studies that followed the same cohorts over time is that global QoL tends to remain high and stable over time but when considering specific areas of QoL, fluctuations exist with some domains increasing in importance (e.g. employment) and other decreasing (e.g. social and sex lives) (Krause & Bozard 2012).
*Note: Krause 1997 used a modified version of the LSQ. Using this version, the authors also observed significant declines in satisfaction related to family relationships, emotional adjustment and control over life.
There is level 2 evidence from one cohort study (Mitchell & Adkins 2010) that aging has greater influence on self-rated health in people with SCI than on those without a SCI.
There is Level 4 evidence from four longitudinal studies (Bushnik 2002; Bushnik & Charlifue 2005; Krause & Broderick 2005; Krause & Coker 2006) that changes in environmental factors over time (i.e., economics, technology) may influence QoL in persons with SCI rather than the aging process per se.
There is Level 4 evidence from three longitudinal studies (Charlifue & Gerhart 2004a; Bushnik & Charlifue 2005; Krause & Bozard 2012) that community reintegration and social participation declines with age after SCI. However, these changes in community reintegration may be similar as compared to the aging general population.
There is Level 4 evidence from seven longitudinal studies (Crewe & Krause 1990; Krause 1992; Krause 1997; Krause 1998; Krause & Broderick 2005; Krause & Coker 2006; Krause & Bozard 2012) that selected domains of life satisfaction change (i.e., social life, sex life, and health decrease, and employment, finances, and adjustment increase) as one ages with an SCI. It may be that these changes in satisfaction of certain domains are comparable to changes in the general population.
There is Level 5 evidence from one cross-sectional study (Kemp & Krause 1999) that age of SCI-onset may be an influential factor on life satisfaction.
There is Level 4 evidence from one longitudinal study (Charlifue & Gerhart 2004b) that previous perceptions of life satisfaction are predictive of later perceptions of life satisfaction.
There is Level 5 evidence from two cross-sectional studies (Kemp & Krause 1999; Barker et al. 2009) that life satisfaction is lower for persons with SCI compared to the general population.
There is Level 4 evidence from two longitudinal studies (Stensman 1994; Putzke et al. 2002a) that previous reports of pain interference after SCI, irrespective of age, are predictive of later pain interference.
There is level 4 evidence from 10 longitudinal studies that individuals with ≤5 YPI have the potential to improve their QoL (Stensman 1994; Kemp & Krause 1999; Bushnik 2002; Putzke et al. 2002b; Bushnik & Charlifue 2005; Krause & Coker 2006; van Koppenhagen et al. 2009; DeVivo & Chen 2011; Kalpakjian et al. 2011; van Leeuwen et al. 2011).
There is level 4 evidence from 4 longitudinal studies that individuals with longer term SCI (i.e., ≥6 YPI) consistently report high and stable QoL levels (Charlifue et al. 1998; Charlifue & Gerhart 2004b; Savic et al. 2010). Similarly, there is Level 4 evidence from one longitudinal study (Pershouse et al. 2012) that QoL remains stable across the lifespan even in those with long-duration SCI.
Selected domains of life satisfaction (i.e. social life and sex life) may decline as one ages with a SCI. Other domains (i.e., employment and finances) may improve as one ages with a SCI. It may be that these changes in satisfaction of certain domains are comparable to changes in the general population.
Changes in environmental factors over time (i.e. economics; technology) may influence QoL in persons with SCI rather than the aging process per se.
Community participation may decline with age after SCI. However, these changes in community participation may be similar to the aging general population.
Individuals with new SCI (i.e. ≤ 5YPI) consistently report improvements to their QoL, whereas individuals with longer term SCI consistently report high and stable QoL over time.
Age of SCI-onset may be an influential factor on life satisfaction.
Previous perceptions of life satisfaction may be predictive of later perceptions of life satisfaction.
Aging has greater influence on self-rated health in people with SCI than those without a SCI.