Abstract
Income volatility is on the rise and presents a growing public health problem. Because in many epidemiological studies income is measured at a single point in time, the association of long-term income volatility with incident cardiovascular disease (CVD) and mortality has not been adequately explored. The goal of this study was to examine associations of income volatility from 1990 to 2005 with incident CVD and all-cause mortality in the subsequent 10 years.
The Coronary Artery Risk Development in Young Adults Study is an ongoing prospective cohort study conducted within urban field centers in Birmingham, AL; Chicago, IL; Minneapolis, MN; and Oakland, CA. We studied 3937 black and white participants 23 to 35 years of age in 1990 (our study baseline). Income volatility was defined as the intraindividual SD of the percent change in income across 5 assessments from 1990 to 2005. An income drop was defined as a decrease of ≥25% from the previous visit and less than the participant's average income from 1990 to 2005. CVD events (fatal and nonfatal) and all-cause mortality between 2005 and 2015 were adjudicated with the use of medical records and death certificates. CVD included primarily acute events related to heart disease and stroke.
A total of 106 CVD events and 164 deaths occurred between 2005 and 2015 (incident rate, 2.76 and 3.66 per 1000 person-years, respectively). From Cox models adjusted for sociodemographic, behavioral, and CVD risk factors, higher income volatility and more income drops were associated with greater CVD risk (high versus low volatility: hazard ratio, 2.07; 95% CI, 1.10-3.90; ≥2 versus 0 income drops: hazard ratio, 2.54; 95% CI, 1.24-5.19) and all-cause mortality (high versus low volatility: hazard ratio, 1.78; 95% CI,1.03-3.09; ≥2 versus 0 income drops: hazard ratio, 1.92; 95% CI, 1.07-3.44).
In a cohort of relatively young adults, income volatility and drops during a 15-year period of formative earning years were independently associated with a nearly 2-fold risk of CVD and all-cause mortality.
