Genetics and Health Insurance: How Genes and Insurance Status Affect Smoking Decisions after Health Shocks

IMPORTANCE Smoking is the leading preventable cause of death in the United States. Experiencing an adverse health shock can serve as an impetus for cessation. Whether this shock can translate into actual behavior change depends on both the insurance status at the time of the shock as well as a genetic predisposition for smoking. OBJECTIVE To understand how the smoking response to a health shock varies depending on health insurance (financial risk) and genetic predisposition for smoking (genetic risk). DESIGN, SETTING, AND PARTICIPANTS Longitudinal study of 3,757 adults in the nationally representative Health and Retirement Study (HRS) who are between 60 and 70 years old, born between 1923 and 1953, observed between 1992 and 2015. Ordinary least squares regression is used to estimate the effect of health shocks for different levels of financial risk exposure and different genetic groups. The differential timing of health shocks before or after the age-based Medicare eligibility threshold for previously uninsured individuals is leveraged to estimate the causal effect of health insurance on behavior change in different genetic groups. EXPOSURES Experiencing a cardiovascular health shock (heart attack, coronary heart disease, angina, congestive heart failure, other heart problems, stroke, or transient ischemic attack), being uninsured prior to becoming eligible for Medicare at age 65, and a measure for high or low genetic risk for smoking based on a polygenic risk score (PGS) for regular smoking. MAIN OUTCOMES AND MEASURES Self-reported current smoking status, and smoking cessation rates. RESULTS For low-genetic-risk individuals (n = 1,883; 887 female; 513 baseline smokers), suffering a health shock while being uninsured decreases the probability of smoking by 32 percentage points (95% CI, -0.58 to -0.06), conditional on baseline characteristics. The effect of the same health shock experienced after age 65 is a 7 percentage point increase in the smoking probability (95% CI, 0.03 to 0.12), showing that Medicare eligibility fully neutralized the reduction in smoking following the health shock (difference: 40 percentage points, 95% CI, 0.13 to 0.67). For high-genetic-risk individuals (n = 1,874; 964 female; 528 baseline smokers), having a health shock does not significantly affect the probability of smoking, independent of the timing (effect when uninsured: -1 percentage point, 95% CI, -0.31 to 0.28; effect when eligible for Medicare: -12 percentage points, 95% CI, -0.32 to 0.09; difference: -11 percentage points, 95% CI, -0.46 to 0.25). The difference in the effect of Medicare eligibility on the smoking response to a health shock between the 2 genetic groups is 50 percentage points (95% CI, -0.94 to -0.06). CONCLUSIONS AND RELEVANCE The determinants of healthy behaviors are complex and multifaceted, and include both biological factors, such as genetic predispositions, as well as environmental factors, such as financial liquidity and health insurance status. We show how the choice of smoking after a serious health shock is jointly determined by the interaction between these biological and environmental components. We find that genetic predispositions can offset the financial incentives for smoking cessation. These results suggest that genetic heterogeneity is a factor that should be considered when evaluating the importance of health insurance policies.