Positive Income Shocks and Accidental Deaths Among Cherokee Indians
A Natural Experiment
Published in: International Journal of Epidemiology, v. 40, no. 4, Aug. 2011, p. 1083-1090
BACKGROUND: Several studies in low-income populations report the somewhat counterintuitive finding that positive income gains adversely affect adult health. The literature posits that receipt of a large portion of annual income increases, in the short term, risk-taking behaviour and/or the consumption of health-damaging goods. This work implies the hypothesis that persons with an unexpected gain in income will exhibit an elevated risk of accidental death—the fifth leading cause of death in the USA. We test this hypothesis directly by capitalizing on a natural experiment in which Cherokee Indians in rural North Carolina received discrete lump sum payments from a new casino. METHODS: We applied Poisson regression to the monthly count of accidental deaths among Cherokee Indians over 204 months spanning 1990–2006. We controlled for temporal patterns in accidental deaths (e.g. seasonality and trend) as well as changes in population size. RESULTS: As hypothesized, the risk of accidental death rises above expected levels during months of the large casino payments (relative risk = 2.62; 95% confidence interval = 1.54–4.47). Exploratory analyses of ethnographic interviews and behavioural surveys support that increased vehicular travel and consumption of health-damaging goods may account for the rise in accident proneness. CONCLUSIONS: Although long-term income gains may improve health in this population, our findings indicate that acute responses to large income gains, in the short term, increase risk-taking and accident proneness. We encourage further investigation of natural experiments to identify causal economic antecedents of population health.