Background
Humans are living much longer today than they did 100 years ago; this great achievement in human development is accompanied by new challenges [
1]. Chronic diseases pose an increasing global problem [
2], and older adults are more vulnerable to such conditions (e.g. cardiovascular diseases, diabetes and lung diseases) [
3].
China has the largest ageing population in the world, and the rate of ageing in this country has accelerated over recent years [
4]. At the end of 2018, the population of China included more than 249.49 million (about 17.9%) people aged ≥60 years [
5]. Approximately 150 million of these older adults have at least one chronic illness [
6]. For decades, research has consistently shown that people with chronic conditions are at greater risk of worse quality of life [
7‐
9] and health outcomes [
10] than are those without chronic disease. Thus, the identification of modifiable factors to prevent the deterioration of health and quality of life among chronically ill older adults is crucial in a time of ageing societies.
Considerable evidence shows that healthy lifestyle habits, such as physical activity and maintenance of a healthy diet, can slow the deterioration of cognitive function, quality of life and physical function in chronically ill (older) populations [
11‐
16]. For example, physical activity has been associated with better cognitive function among older adults with hypertension [
16], and has been found to enhance the quality of life of patients with type 2 diabetes [
12‐
15] and heart failure [
11,
12].
Not only traditional health behaviours (i.e. physical activity, maintenance of a healthy diet and not smoking), but also older people’s ability to stay socially active and connected to others is essential for health and quality of life outcomes. Social participation is considered to be a critical element of active ageing [
17] and has been incorporated into many theoretical models of successful ageing [
18]. It has been associated with longevity [
19], self-rated health [
6], quality of life [
20,
21] and functional ability [
22]. Notably, the positive influence of social participation on health was found to be greatest among older adults [
23]. For example, the association between social participation and cognitive function was shown to be stronger among older adults than among younger persons [
22]. A possible explanation is that active engagement in social activities gives older people opportunities to experience more dynamic environments, which is considered to be beneficial for the maintenance of cognition by stimulating neurogenesis, even at older ages [
22].
Less attention has been paid to whether chronically ill older adults can benefit from social participation [
24,
25]. Several studies have shown that social participation affects the (health-related) quality of life of older adults with arthritis [
26,
27] and post-stroke [
28]. Research on chronically ill older Chinese adults, however, is limited. In the first study of its kind, Hu and colleagues [
29] found no association between social participation and quality of life among older Chinese adults with diabetes. However, their measurement of social participation focused mainly on formal organisations (e.g. sports clubs), which might have led to underestimation and contributed to inaccurate estimation of this association; in China, joining formal social organisations, such as sports clubs and culture associations, is not common [
29], whereas activities such as public square dancing (guang chang wu in Mandarin) [
30], group tai chi practice [
31] and group singing in parks [
32] are common. Furthermore, Hu and colleagues’ [
29] findings were not generalisable to the whole country because of the sampling strategy used.
More importantly, although previous research has identified the importance of traditional health behaviours and social participation separately, no study to date has incorporated social participation as a health behaviour in addition to physical activity, maintenance of a healthy diet and not smoking. Thus, the purpose of this study was to investigate the associations of social participation and these traditional health behaviours with health and quality-of-life outcomes among chronically ill older adults in China, using a large nationally representative dataset.
Discussion
Previous studies have linked social participation to various quality of life and health outcomes among older adults [
20,
21], but not specifically among chronically ill older adults. Moreover, they did not involve the investigation of social participation as a health behaviour in addition to traditional health behaviours (i.e. physical activity, maintenance of a healthy diet and not smoking). In this study, we thus examined the associations of social participation and traditional health behaviours with quality of life and health outcomes among chronically ill older people in China.
We found that the health behaviour social participation was associated significantly with all health and quality of life outcomes examined, which was not the case for traditional health behaviours (smoking, healthy diet, and physical activity). Among all health behaviours, social participation showed the strongest association with better quality of life. In contrast, Hu and colleagues [
29] failed to find an association between social participation and quality of life among older Chinese adults with type 2 diabetes. However, they focused mainly on participation in formal organisations, such as sports clubs, which is not common among older Chinese adults and may have contributed to the lack of association [
29]. In the current study, we incorporated broader aspects of social participation (e.g. working with other neighbourhood residents to fix or improve something and participation in social events in other neighbourhoods), which are more common among older Chinese adults. Our findings extend our understanding of the importance of social participation as an additional health behaviour in chronically ill older populations. Health promotion and lifestyle programmes for such populations should thus address social participation as well as traditional health behaviours.
Physical activity was not associated with cognitive function in our study, in contrast to the previous finding of a positive association among older adults with hypertension [
16]. In an intervention study conducted with diabetic patients [
54], physical activity was related to certain aspects of cognitive function, such as memory and executive function, but was not associated with other aspects (i.e. psychomotor speed and attention/concentration). The inconsistency among findings may reflect the use of different measures of cognitive function. For instance, Frith and Loprinzi [
16] used the digit symbol substitution test, whereas we used a more comprehensive measure of cognitive function. Wu et al.’s [
54] study might partly explain the lack of association in our study because our measure of cognitive function incorporated aspects of attention and concentration, which were shown to be unrelated to physical activity.
In the present study, we observed no association between smoking and any health or quality of life outcome examined in the bivariate correlation and multivariate regression analyses. Similarly, no association has been reported among patients with diabetes [
55,
56] and hypertension [
57]. Nevertheless, in general, smoking has been associated with decreased quality of life among chronically ill patients, including those with diabetes, asthma and lung cancer [
58‐
60]. The reason for the lack of association in our study remains unknown. Research has suggested that smoking intensity (i.e. years of smoking, number of cigarettes per day) influences associations between smoking and health outcomes [
61,
62]. However, most reports do not provide information on smoking intensity, and smoking status has been classified in different ways, making comparison among studies difficult. For example, Xu and colleagues [
57] dichotomized smoking status (‘smoking’ and ‘no smoking’), Danson et al. [
60] used three categories (never, former and current smokers) and we used the most commonly employed dichotomized variable (‘daily smoker’ and ‘not a daily smoker’). Differences in controlling for confounders among studies also may have contributed to the variation in associations [
62]. For example, Danson et al. [
60] study controlled for demographic and clinical variables (e.g. long-term health problems and previous medical conditions), whereas Cataldo et al. [
63] controlled only for age, gender and depression. In addition, the higher mortality rate of heavy smokers may have biased the analyses [
64].
Study strengths and limitations
Our study has several strengths. First, it demonstrated that traditional health behaviours and social participation influenced quality of life and health outcomes in a large nationally representative sample of chronically ill older adults in China. Second, to minimise confounding bias, we included various potential confounders (e.g. socio-demographic characteristics) in the regression model. Third, although we could not assess causality, our findings show that chronically ill older adults may benefit from social participation.
Nevertheless, our findings should be viewed in light of the study’s limitations. As this study was the first to investigate health behaviours of social participation, smoking, physical activity and maintenance of a healthy diet simultaneously with health and quality of life outcomes among chronically ill older adults in China, more research is needed to support our study findings and increase their generalisability. Second, although we followed the WHO’s guideline in defining a healthy diet by measuring fruit and vegetable intake, this measure might be too general, which may have influenced the associations in our analysis. More research is needed to confirm associations with more inclusive dietary criteria, such as those for meat, dairy products, eggs, fish, poultry and soybeans, which are more commonly consumed in China [
65]. Future research also should consider the impacts of the consumption of (certain amounts) of unhealthy foods, such as fatty and high-calorie foods [
66]; diets including large amounts of unhealthy foods should not be considered to be healthy, even when they also include sufficient amounts of fruits and vegetables. Third, due to the cross-sectional design of this study, we could not examine the causality of associations of social participation and health behaviours with quality of life and health outcomes. Social participation and physical function may be reciprocally related [
67]. Future studies should investigate whether changes in social participation and health behaviours are associated with improvements in quality of life and health outcomes among chronically ill patients over time; the effects of changes in health and quality of life outcomes on social participation and health behaviours should also be explored. Finally, we do not know whether or how chronic condition severity and combinations affect health behaviours and health outcomes due to data limitations. Research has suggested that hypertension, chronic hyperglycaemia and atherosclerotic macrovascular disease have a combined effect on cognitive function in patients with type 2 diabetes [
56]. Future studies should consider the potential combined effects of multiple chronic diseases, as multimorbidity is common in older adults.
Acknowledgements
We thank Dr. Yanfei Guo, a specialist at Shanghai Municipal Centre for Disease Control, for his valuable professional explanation of the construction of the China WHO-SAGE data. We are also grateful to the WHO for making the WHO-SAGE dataset publicly available, and to the China Scholarship Council for providing a PhD fellowship for ZF (scholarship No. 201708310108). We also wish to thank Dr. Chunlin Jin, Prof. Shanlian Hu, Dr. Haiyin Wang, Dr. Hai Lin and colleagues at the Shanghai Health Development Research Center for providing support to ZF.
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