Trends in Cardiovascular Risk Factors by Income among Japanese Adults Aged 30-49 Years from 2017-2020: A nationwide longitudinal cohort study

Abstract

Objective: Income is a major social determinant of cardiovascular health. However, individual-level evidence regarding the trends in cardiovascular risk factors by income level among young working-age adults is limited. We thus aimed to examine the trends in cardiovascular risk factors among men and women aged 30-49 years by their income levels. Methods: This nationwide longitudinal study included Japanese adults aged 30-49 years, who annually participated in the national health screening program from 2017 to 2020. Modified Poisson regression models were used to investigate trends in the prevalence of cardiovascular risk factors (obesity, hypertension, diabetes, and dyslipidemia) according to tertiles of individuals’ annual income, adjusting for potential confounders. Results: Among 58 814 adults, 50 024 (85%) were men; the mean (SD) age was 42.1 (5.4) years. Over the study period, the low-income group consistently showed a higher prevalence of obesity, hypertension, and diabetes than the high-income group. The difference in the prevalence of these diseases, particularly hypertension, across income groups increased from 2017 to 2020 among both men (low-income vs high-income: +5.73% [95% CI, 4.72-6.73] in 2017 and +8.26% [95% CI, 7.11-9.41] in 2020) and women (low-income vs high-income: +2.53% [95% CI, 0.99-4.06] in 2017 and +3.83% [95% CI, 1.93-5.73] in 2020). Conclusion: Among adults aged 30-49 years in Japan, a country with a universal healthcare coverage system, we found an increase in the gap of cardiovascular risk factors by income levels over the last 4 years. Careful monitoring of the increasing social disparities is needed to achieve cardiovascular health equity at this life stage.