Differences in Life Expectancy at Birth by Income and Age- and Cause-Specific Contributions: Findings from 8-Year Mortality Follow-Up Data of Nationally Representative One Million South Koreans

INTRODUCTION:  South Korea has national health insurance covering the whole population, an individual linkage system using unique personal identification numbers and a surveillance system for deaths, which provide a unique opportunity to monitor socioeconomic inequalities in life expectancy using nationally representative mortality follow-up data. This study examined differences in life expectancy at birth by income and quantified age- and cause-specific contributions to the differences.

METHODS:  We used 8-year mortality follow-up data (39810 deaths) of nationally representative 2% samples (1025123 subjects in 2002) of total South Koreans. National health insurance premiums were used as marker for income. Age- and cause-specific contributions to differences in life expectancy at birth by income were estimated using Arriaga’s decomposition method.

RESULTS:  Life expectancy at birth gradually increased with income in both genders. Differences in life expectancy at birth between the highest and the lowest income quintile were 7.22 years in men and 3.17 years in women. Most of life expectancy differentials were due to mortality differentials among those aged 40 or over. Cancer (stomach cancer and lung cancer), cardiovascular disease (stroke and ischemic heart disease), external causes (transport accident and suicide), and other causes (liver disease, chronic obstructive pulmonary disease, tuberculosis, and diabetes) were important contributors to the life expectancy inequalities in both genders. Gender differences in the magnitude of life expectancy inequalities by income were mainly due to alcoholic liver disease, stroke, suicide, diabetes, transport accident, chronic obstructive pulmonary disease, stomach cancer, liver cancer, and lung cancer.

CONCLUSIONS:  Income differentials in life expectancy at birth with national health insurance premiums and data linkage systems could provide a valuable opportunity for monitoring and prioritizing population health disparities in South Korea.