Background

Self-rated health (SRH) is one of the most widely used indicators in population health research [1, 2] and is assumed to be a valid measure of the overall global assessment of a person’s current well-being [3]. Traditionally, medical examination data are considered the “gold standard” to measure health or predict disability [4]. However, it has been pointed out that SRH can sometimes be a better predictor of well-being than biological markers and SRH data can be readily collected for large numbers of individuals at minimal cost [5]. The predictive strength of SRH is its multidimensional measurement of healthy aging that incorporates a wide variety of factors [6].

Previous research has found that both chronic life stress and stress from a traumatic shock are strongly associated with poor SRH [7]. In early studies before the 1980s, the majority of research in this area focused on acute stressful life events – for example, natural disasters, combat, and physical assaults [8–11]. However, as modern life fills with increasing pressures, research has drawn attention to the influence of chronic stressors on health outcomes [12–14]. Measures of chronic life stress generally assess the impact of stressors that last for prolonged but often unspecified periods – for example, low socioeconomic status (SES), or poor working condition or long hours [15, 16].

In addition to stress factors, health behaviors have a significant impact on health and are typically measured by factors such as one’s physical activity, diet, alcohol intake, and use of tobacco products. Specifically, eating fruits and vegetables is positively linked to good health [17], while smoking and heavy use of alcohol have a negative impact on health [18]. Physical exercise promotes health by improving physical and cognitive function [19, 20] and provides a means of socializing in an environment charged with positive emotional content [21].

Chronic diseases (i.e., coronary heart disease, diabetes, and depression) tend to be prevalent among older adults and are evidenced to be closely linked with poor SRH among the elderly [22–24]. People with chronic diseases can experience pain and disability that leads to poor SRH. For example, Research has reported that the presence of chronic diseases is one of core predictors of SRH [25, 26].

SRH also has a genetic basis. Nearly a third of the variability in SRH can be attributed to genetic factors [49].

Negative health behaviors, such as lack of exercise, have been considered major factors in determining health outcomes [17, 19]. Physical activity is related to better functioning and overall health status compared with inactivity. Both cross-sectional and longitudinal studies have reported that physical activity delays the deterioration in health status or is related to a better health status compared with unhealthy behaviors [50, 51]. Some studies argue that people do take their health behaviors into consideration when they rate their overall health condition [52].

In interpreting our results, following limitations should take into account. One is that the data on chronic diseases is self-reported based on a person's own understanding of his or her health, which may not be in accordance with the appraisal of medical experts. Although the two evaluations can certainly be combined, major tension often exists between the two perspectives [53]. Another limitation of the study is the lack of neuropathologic conformation of relationships between the APOE4 allele and SRH and between the four chronic diseases and SRH. Although population-based study has sufficient capability to adjust for risk factors, such as genetic, physical, stress, and behavioral factors, general associations need to be followed up with smaller-scale basic science research. Thus, epidemiological and molecular studies are required to define the precise pathway by which the APOE4 allele and chronic disease confers risk of poor SRH and to determine how and why the relationships differ between women and men. Third, the sample size is not large, which prohibited us from examining SRH and its associated factors by subpopulation. Moreover, our analyses have a cross-sectional nature, which are less robust than those based on longitudinal data in studying SRH. Research using longitudinal datasets is thus preferable.

Conclusions

Chronic conditions and the APOE4 allele are associated with significantly increased likelihood of reporting poor health, and the associations appear differently among women and men. To better understand the mechanism on how the respondents self-assess their overall health, models of SRH need to consider chronic conditions and genetic components together with conventional factors such as life stresses or behaviors. Examining the relative associations of those factors with health and well-being could help to optimize and target resources and activities. According to our study, intervention programs should focus principally on older people who suffer from chronic diseases. Further research is also needed to examine older adults’ needs stemming from poor SRH in more depth, with a focus on discrepancies between different groups based on social, genetic, or chronic disease information.