Modifiable risk factors of inequalities in hypertension: analysis of 100 million health checkups recipients.

Inequalities in health behaviors are thought to contribute to inequalities in hypertension. This study examined the extent to which modifiable mediating factors explain income inequalities in hypertension. This repeated cross-sectional study used data from National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB) from 2009 to 2015. Those aged between 40 and 74 were enrollees in the Specific Health Checkups. Hypertension was defined as systolic blood pressure ≥140 mmHg or diastolic blood pressure ≥90, or the use of antihypertensive medication. The mediating effects of exercise, obesity, smoking, and alcohol drinking on the association between income, as an indicator of SES, and hypertension were determined by the Karlson-Holm-Breen (KHB) method. The mean age of the 68,684,025 men and 59,118,221 women was 54.7 (SD = 9.6) and 56.7 (SD = 10.0) years, respectively. Prevalence of hypertension was higher in the lowest income group (48.6% for men, 40.2% for women) than in the highest income group (33.3% for men, 21.5% for women). Inequalities tended to increase over time. Inequalities were larger among those who did not use antihypertensive medication. Modifiable risks explained 10.6% of the association between income and hypertension for men and 15.1% for women. In men, drinking and obesity explained 8.8% and 5.5% of the inequalities in hypertension, respectively. In women, obesity explained 18.8%. Exercise increased the proportion mediated over time. Smoking explained 5.5% among women taking antihypertensive medication. There were health inequalities in hypertension among Japanese adults, and the modifiable risk factors partially explained the inequalities.