The effect of multimorbidity on the gap between global and age-comparative self-rated health scores among the Korean elderly

Most of the behavior change models regard perceived health status as a motivation for healthy behaviors or chronic disease self-management. The aim of this study was to examine the association between the number of chronic diseases and the difference between global and age-comparative self-rated health scores (GSRH and ASRH). We used national representative survey data pertaining to the elderly in 2011 from the Korea Institute for Health and Social Affairs. In total, 10,003 participants (≥60 years old) were selected from those who had completed the survey in 2008. Multinomial logistic regression was used to estimate relative risk ratios (RRR) with 95% confidence intervals. Demographic factors, socioeconomic status, social connection, and healthy life style were adjusted. Individuals with many chronic diseases were more likely to have a positive gap, resulting in a better ASRH score relative to GSRH (p for trend <0.001): 1-2 diseases (RRR = 1.30, 95% CI = 1.07-1.57), 3-4 diseases (RRR = 1.90, 95% CI = 1.55-2.32), and ≥5 diseases (RRR = 1.75, 95% CI = 1.39-2.20). In addition, the association between the number of chronic diseases and a positive gap varied by sex and living area. Our results suggest that a positive gap between GSRH and ASRH that indicates an overestimated age-comparative health, was associated with the number of chronic diseases. Female or urban-living people had stronger associations. Further research is needed to understand how the gap between GSRH and ASRH could be an alternative measure of SRH and a predictor of major health outcomes.