Explaining socioeconomic inequality in mortality among South Koreans: an examination of multiple pathways in a nationally representative longitudinal study.

BACKGROUND: South Korea has a different cause-specific structure of mortality compared with North America and northern European countries where studies on pathways to socioeconomic mortality inequalities have been performed. We examined the ability of multiple pathways to explain socioeconomic differentials in all-cause mortality in South Korea.
METHODS: The 1998 National Health and Nutrition Survey data of South Korea were linked to data on mortality. The socioeconomic position (SEP) indicator was household income. Twelve variables represented biological risk factors (body mass index, systolic blood pressure, cholesterol, and glucose), health behaviours (smoking, alcohol consumption, and regular exercise), psychosocial factors (feelings of sadness and depression, perceived level of stress, and marital status), and early life exposures (education and adulthood height).
RESULTS: Mortality differentials by income level did not decrease after exclusion of subjects with severe chronic illness or functional limitation. Biological risk factors, health behaviours, and psychosocial factors caused minor reductions in relative risk for income levels. The ability of early life exposures to explain socioeconomic differentials in mortality was greater than that of biological risk factors, health behaviours, and psychosocial factors.
CONCLUSIONS: The contribution of multiple pathways to socioeconomic differentials in all-cause mortality may vary in place with the different cause-specific structure of mortality. Future studies with specific pathway variables and specific disease outcomes would provide better understanding of causal mechanisms between SEP and health.