In this study of a community dwelling Korean adult population, SRH was independently associated with hypertension after controlling for other related factors such as age, gender, marital status, education, smoking status, alcohol consumption, physical activity and BMI. Further, there were significant gender differences in the association between SRH and hypertension. SRH was more strongly associated with hypertension in women, compared to men.
Our findings are similar to the results from previous studies suggesting an association between SRH and morbidity or mortality [1
]. According to the study, there was a dose-response relationship, which means that the prevalence of hypertension was highest for the category of very poor SRH and less for fair SRH. However, the mechanisms involved in this relation are still not clear. SRH is a summary statement concerning the ways in which various aspects of health are combined together [21
]. SRH involves subjective as well as objective measures of health and the reliability of SRH has been shown to be high [22
]. Recent studies have attempted to examine the possibility that SRH has a biological basis. While SRH may be associated with inflammatory cytokines in the elderly population, humoral immune markers may be more sensitive to poor SRH in healthy individuals [9
]. In addition, the ways of judging their health status may vary according to gender, age groups, and different social and cultural backgrounds [23
]. Since most studies have been performed in Western populations, this study may contribute to the understanding of SRH in Asian populations. In our study, the distribution of SRH was different between men and women: women were more likely to rate their health status poorer than men. Furthermore, both men and women who were older rated their SRH as poorer than the younger subjects.
Although several studies revealed that the effect of SRH on the prediction of mortality seems to be more apparent for men than women, little is known about gender differences in the association between SRH and hypertension [1
]. While men are likely to rate their health mainly by comparing their health status with the health of other men, women tend to rate their health by considering various sources including the health status of themselves and their family. Men suffer more from life-threatening conditions than women do, but women suffer more from chronic, disabling conditions [24
]. Furthermore, while men tend to reflect mainly serious and life-threatening disease in their assessment of SRH, women tend to reflect both life-threatening and non-life-threatening diseases [19
]. Therefore, poor ratings of health by men may reflect more serious conditions, but those by women may imply more chronic conditions. Women are more likely to include mild diseases in their general health assessment than men. In our study, SRH was more strongly associated with hypertension in women than in men. As hypertension is considered as one of typical examples of chronic disease, the finding may be understood in this context.
This study has several limitations. First, the study was a population-based cross-sectional survey. With this kind of study design, it is often not possible to establish a temporal relationship. To confirm this association, a prospective study needs to be done. Second, there is a possibility of reverse causality; SRH could be not the cause but the outcome for hypertension, because hypertension labeling may adversely affect SRH. Hypertension is an asymptomatic condition that affects 30% or more adults [27
] and most hypertensive individuals remain unaware of their condition [28
]. Since labeled hypertensives are more likely to report poorer SRH than normotensives, the result of this study should be interpreted in caution [12
]. Nevertheless, considering SRH is a proven predictor of mortality and it has been examined as an objective measure of health as well as a subjective measure, SRH may also be considered to be a risk factor for hypertension. Third, the relatively low response rate (41.1%) of invited participants may introduce response bias. However, this is the first report on the association of SRH with hypertension in a Korean adult population. The sample was representative of the source population using the national registration records. Furthermore, information on socio-demographic factors (age, gender, marital status, education) and health behaviors (smoking status, alcohol consumption, physical activity) were collected, and BMI and blood pressure were measured. The related factors were adjusted in logistic regression models. Previous studies have reported SRH as a predictor of mortality mostly in Western populations, but this study revealed the association between SRH and hypertension in an Asian population. In addition, although some studies dealt with SRH as an outcome of hypertension and there was no report on gender differences, this study showed the possibility of SRH as a predictor of hypertension and this association was modified by gender.