Burden of disease associated with lower levels of income among US adults aged 65 and older.

BACKGROUND: Persons aged 65 years and older represent a heterogeneous group whose prevalence in the USA is expected to markedly increase. Few investigations have examined the total burden of disease attributable to lower levels of income in a single number that accounts for morbidity and mortality.

METHODS: We ascertained respondents' health-related quality of life (HRQOL) scores and mortality status from the 2003 to 2004, 2005 to 2006, 2007 to 2008 and 2009 to 2010 cohorts of the National Health and Nutrition Examination Survey (NHANES) with mortality follow-up through 31 December 2011. A mapping algorithm based on respondents' age and answers to the 4 core Healthy Days questions was used to obtain values of a preference-based measure of HRQOL, the EuroQol five dimensions questionnaire (EQ-5D) index, which enables quality-adjusted life years (QALYs) to be calculated. We included only respondents aged 65 years and older at the baseline, yielding a total sample size of 4952. We estimated mean QALYs according to different categories of income based on the percentage of Federal Poverty Level (FPL).

RESULTS: After adjusting for age, gender and education, the remaining QALYs decreased with each successive decrement of category of income, ranging from 18.4 QALY (≥500% FPL) to 8.6 QALY (<100% FPL). Compared with participants with a mean income of ≥250% FPL, participants with an income <250% FPL had significant losses in QALY for most of the sociodemographic groups examined. In contrast, persons with a lower educational attainment did not show a corresponding loss in QALY according to income category.

CONCLUSIONS: This study confirmed the association between lower income category and greater burden of disease, as measured by QALYs lost, among the US population aged 65 years and older. Our findings provide additional evidence of the role played by other key determinants of health and how factors not traditionally addressed by the healthcare system impact the life cycle of individuals and communities.