Age- and cause-specific contributions to income difference in life expectancy at birth: findings from nationally representative data on one million South Koreans.

BACKGROUND Income is not frequently used to monitor health equity on a national level largely due to the lack of public data on income. Information on income allows policy makers to identify the economically disadvantaged population in a country directly. We examined differences in life expectancy (LE) at birth by income and quantified age- and cause-specific contributions to the LE differences using national health insurance data. METHODS Data from a nationally representative sample of 1 097 333 South Koreans (2% of the total population) collected between 2002 and 2010 (39 737 deaths) were used. National health insurance premiums were used to estimate income level. Age- and cause-specific contributions to differences in LE at birth by income were estimated using Arriaga's decomposition method. RESULTS LE at birth gradually increased with income in both genders. Interquintile income LE differences were 7.93 years in males and 3.82 years in females. Most of LE differentials were attributed to differences in mortality in middle-aged and older adults. Suicide and cerebrovascular accidents were the two leading causes of death contributing the most to income LE differences in both males and females. The top 10 causes of death accounted for over 50% of the total LE differences by income in both genders. Alcohol-related causes of death explained the majority of the gender differences in the income LE differentials. CONCLUSIONS Income differentials in LE at birth according to national health insurance premiums and data linkage systems could provide a valuable opportunity for monitoring and prioritizing population health inequalities in South Korea.