Does social participation reduce the risk of functional disability among older adults in China? A survival analysis using the 2005–2011 waves of the CLHLS data

The influence of social participation on functional ability has been widely discussed in developed countries. According to social integration theory, social engagement gives meaning to an individual’s life by enabling him or her to participate in it fully, to be obligated, to feel attached to one’s community, and to feel fulfilled, which are all beneficial to health. Social relationship can also shape health-related resources that are available and increase motivation and social pressure to take good care of one’s health [14, 15].

In support of social integration theory, existing studies in developed countries consistently show that extensive engagement in social activities is associated with a low likelihood of functional disability among older adults [16‐19]. For instance, a study on older Japanese reveals that membership in multiple social organizations is associated with a reduced risk of having incident functional disability possibly because participation in various social activities enables older people to take on multiple social roles [17]. Moreover, these studies indicate that social participation benefits the functional ability of older adults through psychosocial, behavioral, and physiological pathways. First, engagements in social activities may benefit the health of older adults by helping them find social and spiritual supports, thereby reducing mental health problems. Studies provide sufficient evidence that high levels of social participation reduce the likelihood of having mental health problems [20] and self-destructive habits [21], and that mental distress has negative effects on physical health. Moreover, involvement in social activities can help older adults lower the risk of functional disability by maintaining cognitive ability [15]. Second, the underlying linkage between social participation and one’s functional health can be explained by engaging in protective health behaviors [22]. For instance, participation in community voluntary works can benefit the functional health of older adults by staying physically active [23]. Third, social participation may exert direct physiological benefits, such as buffering stress, boosting host resistance, and lowering the biomarkers of disease risks [24].

While most studies use an aggregated indicator of social participation (i.e., number of social activities) [25] or focus on one of its particular types, recent studies have also shown that the relationship between social participation and functional decline differs by types of social activities probably because different social activities play different roles in health prevention [17]. Engagement in leisure-time activities may encourage people to stay physically active and reduce the risk of developing functional disabilities [26]. In addition, participating in organized social activities, such as church attendance and group voluntary activities, could confer health-enhancing benefits through psychosocial pathways, such as having considerable chances to socialize with others aside from family members and obtaining a sense of motivation, inner direction, and purposefulness [27]. A longitudinal study indicates that older adults who engage in volunteering activities have good self-rated health, few depressive symptoms, and good functional abilities possibly because volunteering provides them a chance to take on new roles that are psychologically rewarding [28]. Furthermore, participating in productive activities, such as paid work, is negatively related to the onset of functional decline probably by preserving one's physical and cognitive abilities [29]. Engagement in paid work also means having considerable individual/social resources, which may help in maintaining good health [30]. Although the empirical investigations into the mechanisms through which different types of social participation affect the risk of functional disability among older adults can provide evidence for health promotion, this important issue is understudied in the existing literature.

Research on the relationship between social participation and functional disability among Chinese older adults is limited. A cross-sectional study based on the nationally representative data reveals that the frequency of participation in various social activities, such as interacting with friends, playing mahjong, volunteering, and other activities, is positively related to the functional ability of older adults. Positive social interactions gained from involving in these activities may provide one of the explanations for the beneficial effects of social participation on functional ability [13]. Another cross-sectional study contends that re-entering into the labor force after retirement is positively related to the functional health of Chinese older adults [31]. These studies provide important evidence for the relationship between social participation and functional health among Chinese older adults, but research based on cross-sectional data may have the problem of reverse causality. Losses in physical function and self-care capacities may lead to reduced social participation; hence, social participation may be more of a consequence of functional disability than it is a cause.

The social and structural contexts of social participation among older adults in China are different from those in developed countries, and the observed relationship between various types of social participation and functional disability in developed countries may not be applicable to Chinese older adults. The Chinese cultural tradition of familism encourages bonds within family and kinship. Thus, informal social interactions among immediate family members and relatives are the most important aspects of social relationships for Chinese older adults. Civil society is still at its early stage of development such that voluntary activities organized by social organizations or self-help groups are rather limited. Cultural and leisure-time activities, such as group dancing, singing, and playing cards/mahjong that are organized by older adults themselves, and formal social or voluntary activities, such as health lectures, trainings on using smartphones, and security patrols organized by residential committees, are the major forms of social activities that Chinese older adults are involved in [32]. Although participation in paid work is an indispensable part of social participation among Chinese older adults, their level of participation in the paid employment is low. China has an early mandatory retirement age such that men retire at 60 years old and women retire between 50 and 55 years old. The opportunities for relocating paid jobs are rather limited among retirees. Although some studies show that participation in paid job is beneficial to health among older adults in China, other studies indicate that Chinese older adults who remain in the paid job after retirement tend to have insufficient financial support and poor health conditions [33, 34]. Older adults who participate in paid jobs available to them after retirement are likely to experience burnout that offsets the beneficial effects of employment on health. On the basis of the existing literature and Chinese social and cultural backgrounds, the present study hypothesized that informal social interactions, group leisure-time activities, and organized social activities are negatively related to functional decline and that paid work is not related to functional ability among Chinese older adults. We also anticipated that extensive social participation has a strong negative relationship with functional decline because taking on multiple social roles may have overlapping health benefits.

Data for this study were obtained from the 2005, 2008, and 2011 waves of the Chinese Longitudinal Healthy Longevity Survey (CLHLS). The CLHLS is a randomly selected sample of rural and urban older adults in 631 countries/cities of 22 provinces, which represents 85% of the total population in China. A detailed description of the sampling design and data quality of the CLHLS has been reported elsewhere [35]. The 1998 baseline and 2000 follow-up surveys of the CLHLS included approximately 10,000 respondents aged 80 years and over. The CLHLS started to interview younger-old persons in 2002. At each wave, survivors were re-interviewed, and the deceased interviewees were replaced by additional participants. The CLHLS collected information on socio-demographic characteristics, physical and mental health status, chronic diseases, family and social supports, and health behaviors.

This study used the fourth, fifth, and sixth waves because the wording of the questions on social participation and functional ability was consistent in the three waves. The CLHLS conducted face-to-face interviews with 15,638, 16,540, and 9765 individuals in 2005 (baseline), 2008 (Time 2), and 2011 (Time 3), respectively. To select an initially nondisabled group, we excluded 25 respondents whose age was below 65 and 3929 respondents who reported having problems with at least one activity of daily living in 2005. We also dropped 840 cases with missing information for independent and dependent variables, leaving a baseline sample of 10,844. After merging the baseline data with 2008 and 2011 waves, the number of respondents who survived and were surveyed in all three waves was 3731 (38.6% of the baseline sample). Compared with those who dropped out of the sample, the remaining participants were significantly more likely to be younger and married, reside in rural areas, have more children, have better education and cognitive and emotional conditions, and engage in all types of social activities and informal social interactions more actively (results shown in Appendix). Therefore, the observed association between social participation and functional disability in the present study may be underestimated.

The survival analysis method was used given its advantage in predicting the influence of social participation on the onset of functional disability. The 7-year follow-up period was divided into 3-month intervals, and the respondents who did not have incident functional disability during the period were censored. First, a description of sample characteristics was presented. Second, we estimated the bivariate association between the different types of social participation and the onset of functional disability using life table analyses. Third, given that the dependent variable (i.e., time for the onset of functional disability) was a dichotomous measure, we used discrete hazard models to estimate the effect of social participation on the onset of functional disability after adjusting for the mediating factors and other covariates. A nested modeling approach was used to assess the mediating effect of the behavioral and psychosocial factors in the relationship between social participation and functional decline. We sequentially added behavioral and psychosocial factors in models 3 and 4 to identify the changes in HR estimates associated with various types of social participation. Finally, we calculated the mediating effects by using Sobel’s test. The proportion of risk reduction for the onset of functional disability that was explained by each potential mediating factor was computed as follows: [(HR_{basic model} − HR_{adjusted model}) / (HR_{basic model} − 1)] * 100% [38]. Given the possible reciprocal relationship between social participation and functional disability, social participation, behavioral and psychosocial mediating factors, and some covariates were treated as time-varying variables, which can provide accurate prediction for the relationship between social participation and functional decline.

Table 1 presents the distribution of sample characteristics. Respondents aged 80 years or older accounted for 44.6% of the entire sample. More than half of the respondents were women (51.7%), unmarried (51.2%), and residents of rural areas (53.2%). A total of 44.2% of the older adults were illiterate. Most of the respondents perceived their economic conditions as “fair” (68%), whereas 16% considered their economic status as “poor.” The average number of living children was 3.9. The respondents reported having 1.2 diagnosed chronic diseases on average.

The overall level of social participation was low with an average number of social activities participated of 0.9 out of a total score of 4 (Table 1). The mean scores for group leisure-time activities (i.e., playing cards/mahjong) and organized social activities were 0.6 and 0.4 (out of a range between 0 and 4), respectively. The level of informal social interactions was also low with an average number of siblings frequently visited of 0.7 (out of a range of 0 and 8). Only 5.8% of the respondents were involved in paid jobs. Table 1 also shows that 42.8% of the respondents engaged in physical exercise. The average scores of the cognitive ability and positive emotion indices were 20 (for a range between 0 and 23) and 11.5 (for a range between 3 and 15), respectively, reflecting good overall cognitive and emotional conditions among older adults.

Figures 1, 2, 3 and 4 provide graphical displays of cumulative survival probability for the onset of functional disability by different types of social participation among older adults over the 7-year period. The figures illustrate that the cumulative survival steeply declined among those who lack of or had low levels of social participation, and that the pattern was consistent for four types of social activities. Particularly, Figs. 1 and 2 depict that the cumulative survival for older persons who never played cards/mahjong or who did not participate in organized social activities declined more rapidly than that for those who participated in these activities frequently. Figure 3 shows that people who were not frequently visited by siblings had a higher probability of having functional disability compared with those whose siblings frequently visited. Figure 4 indicates that the cumulative survival probability for older persons who were not involved in paid jobs was smaller than that for people who were involved in paid jobs.

The results from the univariate discrete time hazard regression models were consistent with the results from life table analyses (Table 2). The first column of Table 2 shows that extensive social participation had a strong negative association with the onset of functional disability. Moreover, playing cards/mahjong, engaging in organized social activities, and being frequently visited by siblings were all significantly related to the reduced risk of having incident functional disability, whereas participation in paid jobs was not significantly associated with the risk of functional decline.

In multivariate discrete time hazard regression analyses (Table 2), extensive social participation was significantly associated with a decreased risk of functional decline after adjusting for socio-demographic characteristics, health status, and behavioral and psychosocial factors (HR = 0.92, p < 0.001) (Model 1). In Model 2, regular participation in cards/mahjong playing (HR = 0.78, p < 0.001) and organized social activities (HR = 0.78, p < 0.001) and frequent visits by several siblings (HR =0 .75, p < 0.001) were all significantly associated with decreased risks of functional decline after controlling for socio-demographic characteristics and health status. However, involving in paid jobs was not significantly related to functional decline. Model 3 indicates that, after adding physical exercise in the model, the significant association between participation in group leisure-time activities (HR = 0.79, p < 0.001) and organized social activities (HR = 0.83, p < 0.01) with functional disability still remained, but the magnitude of the associations was slightly reduced. Model 4 shows that, when cognitive ability and positive emotions were added in the model, the magnitude of the association between participation in group leisure-time activities (HR = 0.84, p < 0.001) and organized social activities (HR = 0.86, p < 0.05) with functional decline was further reduced but still remained significant. A significant inverse relationship between frequent visits by siblings (HR = 0.76, p < 0.001) and the onset of functional disability was observed even after controlling for the effects of behavioral and psychosocial factors and other covariates, and the magnitude of the association remained similar across Models 2 and 4.

Moreover, engagement in physical exercise (HR = 0.61, p < 0.001) was associated with a low risk of functional decline. Having good cognitive ability (HR = 0.92, p < 0.001) and a high degree of positive emotions (HR = 0.89, p < 0.001) were both significantly related to a reduced risk of functional disability (Model 4). Model 4 also indicates that older adults who were 70 years or older or literate (HR = 1.37, p < 0.01), who lived in urban areas (HR = 1.78, p < 0.001), or who had more chronic diseases (HR = 1.25, p < 0.001) tended to have higher risks for the onset of functional disability than those in reference groups.

We further explored the potential mediating effects of behavioral and psychosocial factors on the relationship between various types of social activities and functional decline. Table 3 reveals that cognitive ability had the strongest mediating effect for the association between playing cards/mahjong and the onset of functional disability, accounting for 18.9% of the association, followed by positive emotions (7.0%) and physical exercise (5.4%). The inverse relationship between engaging in organized social activities and the risk of functional decline was largely explained by physical exercise (25.7%) and cognitive ability (17.7%). Behavioral and psychosocial factors also had significant mediating effects for the association between the number of siblings frequently visited and the onset of functional disability, but the magnitude of the mediating effect was modest. Thus, further studies are needed to explore possible intervening factors between informal social interactions and functional disability among older adults.