Socioeconomic Inequality in mortality using 12-year follow-up data from nationally representative surveys in South Korea

BACKGROUND Investigations into socioeconomic inequalities in mortality have rarely used long-term mortality follow-up data from nationally representative samples in Asian countries. A limited subset of indicators for socioeconomic position was employed in prior studies on socioeconomic inequalities in mortality. We examined socioeconomic inequalities in mortality using follow-up 12-year mortality data from nationally representative samples of South Koreans. METHODS A total of 10,137 individuals who took part in the 1998 and 2001 Korea National Health and Nutrition Examination Surveys were linked to mortality data from Statistics Korea. Of those individuals, 1,219 (12.1 %) had died as of December 2012. Cox proportional hazard models were used to estimate the relative risks of mortality according to a wide range of socioeconomic position (SEP) indicators after taking into account primary sampling units, stratification, and sample weights. RESULTS Our analysis showed strong evidence that individuals with disadvantaged SEP indicators had greater all-cause mortality risks than their counterparts. The magnitude of the association varied according to gender, age group, and specific SEP indicators. Cause-specific analyses using equivalized income quintiles showed that the magnitude of mortality inequalities tended to be greater for cardiovascular disease and external causes than for cancer. CONCLUSION Inequalities in mortality exist in every aspect of SEP indicators, both genders, and age groups, and four broad causes of deaths. The South Korean economic development, previously described as effective in both economic growth and relatively equitable income distribution, should be scrutinized regarding its impact on socioeconomic mortality inequalities. Policy measures to reduce inequalities in mortality should be implemented in South Korea.