Self-rated health and mortality in a prospective Chinese elderly cohort study in Hong Kong
Introduction
Self-rated health (SRH), a subjective assessment of health status, is a powerful predictor of mortality in older persons. SRH is as an important health indicator which is easy to measure and provides a good reflection of health status (de Bruin et al., 1996). SRH may be assessed as global SRH using questions such as “What do you think of your health in general?” (Eriksson et al., 2001, Idler and Benyamini, 1997) or as comparative SRH, including age-comparative SRH (comparing oneself to other people of the same age) and self-comparative SRH (comparing oneself to one's own status a year earlier) (Alfonso et al., 2012, Fernández-Ruiz et al., 2013). In the West, measurement methods for SRH such as type of scale, wording of the question and number of options differ; both global and age-comparative SRH predict death (Fernández-Ruiz et al., 2013, Lima-Costa et al., 2012, Young et al., 2010) although comparisons are not always consistent. Sargent-Cox et al. (2010) reported that global SRH was a better predictor of all-cause mortality than age-comparative SRH while Fernández-Ruiz et al. (2013) reported that age-comparative SRH was better. However, self-comparative SRH is a weaker predictor of mortality (Bath, 2003, Fernández-Ruiz et al., 2013). The magnitude of association of SRH with mortality may vary by cause of death. SRH might be more strongly associated with diseases with a prolonged course and substantial impact on daily life, such as cardiovascular and respiratory diseases, than diseases without notable signs in the early stages which then develop rapidly such as cancer (Fernández-Ruiz et al., 2013). SRH is easy to measure, and could be a health indicator for older people given it might reveal health status before symptoms develop.
Most studies of the association of SRH with mortality relate to Western populations, where associations may vary by socioeconomic position (Burström and Fredlund, 2001, Huisman et al., 2007, Møller et al., 1996, Mossey and Shapiro, 1982). However, these observations may not generalize to other settings because of contextually-specific cause-composition of mortality, culturally-specific perceptions of health and varying social patterning of health-related attributes. In the West, cardiovascular disease is the leading cause of death, but cancer is the leading cause of death in Hong Kong (Lozano et al., 2013). Moreover, self-ratings tend to be optimistic in the West (Heistaro et al., 2001, Montlahuc et al., 2011) but other cultures may favor moderation, such as the Chinese “doctrine of the mean” (Leung, 2010, Li et al., 2004, Moore, 1967) which may make people rate their health as “normal”. Finally, socioeconomic patterning may be less entrenched in settings where economic development is recent (Maddison, 2007) and socioeconomic disadvantage has not been perpetuated over generations. Few studies have addressed the association of SRH with mortality in non-Western settings, often with short follow-up and small samples (Ho, 1991, Leung et al., 1997). We have previously reported that age-comparative SRH was more strongly associated with concurrent physical conditions than self-comparative SRH (Li et al., 2006) as well as that depression was associated with SRH and mortality (Sun et al., 2013). Here, we examined the role of SRH in predicting death from all- and specific causes in a developed non-Western setting, where cardiovascular disease is not the leading cause of death (Lozano et al., 2013), cultural preferences emphasize moderation (Leung, 2010, Moore, 1967) and universal education is recent (Johnson, 1998). We also examined whether any associations varied by socioeconomic position.
Section snippets
Source of data
Since July 1998, eighteen Elderly Health Centers (EHC) have been established by the Hong Kong Government Department of Health to offer older people screening services and medical examinations, aiming to enhance primary health care by improving self-care ability, encouraging healthy living and strengthening social integration. All residents of Hong Kong aged ≥ 65 years were encouraged to enroll for a small annual fee of HK$110 (US$1 = HK$7.8; waived for those on public social security assistance).
Results
Among 66,820 participants (22,680 men and 44,140 women) enrolled at baseline from 1998 to 2001, 66,814 (99.9%) with age- and self-comparative SRH were included here. Of 66,820 participants, 62,824 had vital status ascertained from record linkage including 19,452 deaths, 2539 had vital status obtained by telephone interview including 393 deaths, and 1457 had unknown vital status and were presumed to be alive. The mean follow-up was 10.9 years (standard deviation = 3.1). Of the 19,845 deaths, 6336
Discussion
In this understudied non-Western population, age-comparative SRH predicted death in older people after adjusting for age, sex, socioeconomic position, lifestyle, BMI, depression and objective health status, indicating that age-comparative SRH may act as a proxy of unmeasured signs or symptoms of diseases as age-comparative SRH was also strongly related to objective health status. The association was stronger for death from cardiovascular disease and respiratory disease than for death from
Conclusion
In Hong Kong, the most westernized city of China, age-comparative SRH predicted death among older people although the magnitude of association was smaller than that in Western populations, possibly because of a different cause-composition of mortality, long life expectancy or contextually specific assessments of health. Consistent with Western studies, age-comparative SRH also predicted death from cardiovascular and respiratory diseases more strongly than death from cancer. The association of
Conflict of interest
The authors declares that there is no competing interests.
Acknowledgments
We wish to thank the staff of the Elderly Health Centers and the Hospital Authority for their assistance in data collection and entry.
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