17 Year Study Shows Changes in Income Can Influence the Occurrence of Cardiovascular Disease

A study led by Mr. Stephen Wang, published in JAMA Cardiology, showed that an income drop over 6 years was associated with an increased incidence of cardiovascular disease over the next 17 years. Additionally, an increase in income over 6 years was associated with a reduced incidence of cardiovascular disease over the same time period. The findings of this paper suggest that changes in income can have an effect on a person’s health.

Socioeconomic status (SES) has been known to be associated with a wide variety of diseases. Low income has previously shown to be associated with myocardial infarction, heart failure, and stroke. Additionally, a lower SES is associated with depression, another cardiovascular risk factor. While there is a lot of evidence to support the association between SES and cardiovascular disease, whether this association is causal is not known. One possible explanation is that a low income is a marker that indicates worse health-related behaviors. In order to further support the idea of the two variables being causal, changes in SES, and whether that impacts health, needs to be observed. In this study, the investigators aimed to determine whether a drop or increase in income would lead to a change in the incidence of cardiovascular disease.

The Atherosclerosis Risk in Communities (ARIC) study is a prospective cohort study that enrolled 15,792 participants between the ages of 45 and 64. Risk factors, health behaviors, and comorbidities were all assessed. Patients were followed for up to 17 years from the time of enrollment. Patients who did not complete their follow up or who had a history of myocardial infarction, stroke or heart failure at baseline were excluded. Patients reported their family income over the 12 months prior to the first visit. A change in income over the first 7 years was assessed. The investigators adjusted for various sociodemographic variables including age, sex, race/ethnicity, education level, and occupation. Patients who were retired during the initial part of the follow-up and those with missing data were excluded. The primary outcome was the occurrence of a cardiovascular event, including probably myocardial infarction, fatal cardiovascular event, incident heart failure, and probable or definite stroke.

Of the 15,792 ARIC participants, 8,989 were included in the final analysis. The mean age at enrollment was 53 years. 20% were black and 43% were men. A total of 900 (10%) experienced an income drop, 70% had incomes that were relatively unchanged, and 20% experienced a rise in income. Those with an income drop had a higher risk of a cardiovascular event when compared to those whose income was unchanged (HR 1.17, 95% CI 1.03-1.32). Those with an income rise had a lower incidence of cardiovascular events as compared to those whose income was not changed (HR 0.86, 95% CI 0.77-0.96). Finally, the authors noted that there was a significant interaction between race and income drop (p for interaction = 0.03). White participants who had a decrease in income had a higher risk of a cardiovascular event when compared to black participants. Additionally, women who had an increased income had a lower incidence of a cardiovascular event when compared to men who had an increased income.

The investigators found that patients who had a decrease in income had a higher risk of developing a cardiovascular event in the future. Additionally, those who had an increase in income had a lower risk of a subsequent cardiovascular event. When describing the potential mechanisms that could explain this, Mr. Wang noted, “An unanticipated drop in income may induce changes in health behaviors. For example, income loss has been associated with a shift toward consumption of less healthy foods, eg, foods that are more energy dense and yield more calories for a given price. Income drops may also result in loss of health insurance coverage, although we did not observe that in this study population. Large drops in income may also lead to financial stress and worry, which are in turn linked to stress-coping behaviors such as increased intensity of cigarette smoking and alcohol use.” However, this study does have its limitations. There was no standard definition for what constituted a significant change in income. Also, income is dynamic and there may have been additional changes in income that were not captured. Finally, income change was assessed over a relatively short period of time. Even when considering these limitations, the study reinforces the need to be aware of financial changes in patients’ lives and how those changes can impact health.