The risk for cardiovascular disease and all-cause mortality have been correlated with income drops and volatility, according to a study published in Circulation.
Among those with 15 years of volatile income, this risk was nearly doubled in the subsequent decade, underscoring the need for further research given increasingly volatile income in the current economic age.
This prospective cohort study included 3937 participants (47.6% black, 23 to 35 years old at baseline in 1990; 56.2% women). The study was conducted in Oakland, California; Birmingham, Alabama; Chicago, Illinois; and Minneapolis, Minnesota, from 1990 to 2005 (income tracking period) and from 2005 to 2015 (cardiovascular outcome period). Follow-up took place over 30 years, with 6-month check-ins on contact information and vital status and yearly check-ins on cardiovascular health.
A decrease of at least 25% between visits that was below the average income during the study period constituted an income drop. Data on fatal and nonfatal cardiovascular events, as well as all-cause mortality, were gathered through a variety of methods including phone calls, death certificates, and medical records. Incidence density rates for cardiovascular events and all-cause mortality were computed per 1000 person-years, stratified by economic predictor category, whereas their risk was computed using Cox proportional hazards models stratified by economic predictors.
Between 2005 and 2015, there were 106 cardiovascular events (2.76 per 1000 person-years) and 164 all-cause deaths (3.66 per 1000 person-years), with higher rates among those with higher income volatility and the number of income drops (P <.01 for both). High-income volatility correlated with being black and female, having low education, being a current smoker, and being unemployed and unmarried. Higher cardiovascular risk was associated with greater income volatility (hazard ratio [HR], 2.07 for high vs low volatility; 95% CI, 1.1-3.9) and a greater number of income drops (HR, 2.54 for ≥2 vs no income drops; 95% CI, 1.24-5.19). All-cause mortality was similarly associated with greater income volatility (HR, 1.78; 95% CI, 1.03-3.09) and greater number of income drops (HR, 1.92; 95% CI, 1.07-3.44).
Limitations to this study included ethnic/racial sampling confined to blacks and whites, a relatively young sample, and the potential for reverse causation to influence the interpretation of results.
The study findings “reinforce the urgency and growing public health threat associated with income volatility in the United States,” the authors concluded. “Our findings show that high- vs low-income volatility from 1990 through 2005 is associated with a nearly twofold risk of [cardiovascular disease] and all-cause mortality in the subsequent 10 years. Given the current economic environment of increasing income instability, understanding how income volatility is associated with health has become increasingly important.”
Elfassy T, Swift SL, Glymour MM, et al. Associations of income volatility with incident cardiovascular disease and all-cause mortality in a US cohort: 1990 to 2015 [published online January 7, 2019]. Circulation. doi: 10.1161/CIRCULATIONAHA.118.035521