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According to data from the National Center for Health Statistics, the long-term trend toward rising life expectancy in the United States has stalled in the past decade. Life expectancy at birth was 78.9 years in 2014 and has worsened every year since; it was 78.6 years in 2017. While so-called deaths of despair from drug and alcohol use and from suicide are major factors in this worsening, the decline in the age-adjusted death rate from cardiovascular disease (CVD) that began in the 1970s has stalled in the same time frame, with no statistically significant change between 2016 and 2017 and an actual increase between 2014 and 2015. Deterioration in the quality of medical care is an implausible explanation for these trends, so attention has been turned increasingly toward social determinants of health as the cause. In this view, increased risk for chronic noncommunicable illnesses, such as CVD, falls on those with lesser socioeconomic positions as judged by factors such as educational attainment, income/wealth, race/ethnicity, and political voice.1
In this issue of JAMA Cardiology, Wang et al2 provide valuable supporting evidence for this view and add nuance to our understanding of the association between socioeconomic position and health outcomes. Using data from the Atherosclerotic Risk in Communities (ARIC) study, they assessed the association of a large income change with subsequent incidence of cardiovascular disease. In the subset of 8989 ARIC individuals in their defined cohort, 10% experienced an income drop of at least 50%, and 20% had an income rise of at least 50% between the baseline (1987-1989) visit and the second follow-up visit 6 years afterwards. They were careful to exclude those with incident CVD between the visits to minimize the likelihood of confusion from reverse causation, where illness causes income drop rather than the reverse. They controlled for an inclusive set of risk factors for CVD and also for other markers of socioeconomic position including education, occupation, and race/ethnicity. They appropriately controlled for baseline income. Although there were statistically significant differences in the characteristics of those with large decreases compared with those with large increases, the differences were subtle; those experiencing income drops were slightly older, less well educated, and more likely women. Those with a large income decrease were more likely to develop myocardial infarction, stroke, heart failure, or cardiovascular death compared with those whose income did not change, while those with a large income increase were at lower risk of reaching the end point over the subsequent 17 years. In a sensitivity analysis with income shifts of 25%, the direction and magnitude of the change in risk were consistent with these findings but did not reach statistical significance. We can be confident in the veracity of the results.
This analysis extends results linking low income with CVD. Differences in health outcomes associated with low income appear to have worsened in the United States as income inequality has grown. In one example, Chetty et al3 showed for the period 2001 to 2014 that estimated life expectancy increased 2.91 years for women in the top 5% of the income distribution and only 0.04 years for women in the bottom 5%; it increased 2.34 years for men in the top 5% and only 0.32 years for men in the bottom 5%. This analysis also extends results reported by Elfassy et al4 and Pool et al5 on the associations between income change and health outcomes. Elfassy et al4 used data from the Coronary Artery Risk Development in Young Adults Study (CARDIA) to examine the association between income changes and subsequent CVD events, reporting that those with a greater number of income drops of greater than 25% and those with greater standard deviation of income over a 15-year period had a higher likelihood of CVD events. Pool et al5 examined the association between a loss of more than 75% of net wealth and all-cause mortality among individuals in the Health and Retirement Study; the adjusted hazard ratio for mortality was 1.50 compared with those who did not have large drops in wealth and was similar to those who remained continuously in poverty.
One question this article raises is why there is an association between income shift and CVD; understanding the mediators of the association is important for developing strategies to mitigate impact. There are several possibilities. First, income shift might be a marker of an event that has a more direct effect on cardiovascular health. Death of a spouse or divorce is a likely cause of an income fall while marriage might lead to an income rise. Second, chronic stress associated with a sudden change in material resources might lead to chronic activation of the sympathetic nervous system and the adrenal cortex (allostatic load), which in turn has been hypothesized to lead to CVD. Third, a fall in income might lead to a diminished ability to recruit health care resources; loss of health insurance is an obvious means for this possibility. A less obvious means is the effect of financial stress on cognitive function. In one rather striking laboratory experiment,6 participants were presented with hypothetical scenarios describing varying levels of financial stress. Participants with low income had poorer performance on a series of cognitive tasks after exposure to stressful scenarios, while upper-income participants did not have that deterioration in performance. Thus, financially stressed individuals may have more difficulty with making use of health care resources by keeping medical appointments and adhering with medications.
The broader question this article asks us is how we as physicians should respond to a societal problem that leads to illness. We have taken strong stands when societal problems have been things such as smoking or childhood obesity, but our path has been less clear when the problems veer more toward the political. Few physicians question our responsibility to advocate for public efforts to decrease smoking rates, but many would question a responsibility to advocate for greater economic security. However, the choice between plunging into political discussions and avoiding the discussions altogether is a false one. We as a profession have a responsibility to promote full understanding of the health effects of the social structure we as a society have chosen. Results, such as those put forward by Wang et al,2 are clearly a step in that direction.
Corresponding Author: Edward P. Havranek, MD, Department of Medicine, Denver Health Medical Center, 601 Broadway, Mailcode 4000, Denver, CO 80204 (firstname.lastname@example.org).
Published Online: October 9, 2019. doi:10.1001/jamacardio.2019.3802
Conflict of Interest Disclosures: None reported.
Havranek EP. The Influence of Social and Economic Factors on Heart Disease. JAMA Cardiol. 2019;4(12):1212–1213. doi:10.1001/jamacardio.2019.3802
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