U-shaped association between blood pressure and all-cause mortality in older adults: the Shizuoka study.

Low blood pressure (BP) is suggested to be associated with all-cause mortality in older adults. The aim of this study is to validate the relationship in older adults and to examine the possible involvement of clinical characteristics, namely functional disability, comorbidities, antihypertensive treatment, and reverse causation, in the relationship using insurance claims data including annual health checkup data. The study participants were 337,975 individuals aged ≥65 years. The earliest day of participation in the annual health checkup from 2012 to 2020 was determined at baseline. Data on comorbidities, functional disability levels, prescribed antihypertensive medications, and incidence of stroke, myocardial infarction and all-cause mortality were obtained from the insurance claims. During a mean follow-up period of 5.3 years, there were 27,495 cases of all-cause mortality, 9000 cases of stroke and 1640 cases of myocardial infarction. A U-shaped association was observed between systolic BP and all-cause mortality in participants aged ≥75 years and the hazard ratio calculated systolic BP 120-129 mmHg as reference was 1.14 for <110 mmHg and 1.16 for ≥150 mmHg (all P < 0.001). The U-shaped association remained significant in the sub-analyses of individuals without severe comorbidities, antihypertensive treatment, or functional disability. Similar results were observed in the analysis excluding early-mortality cases. In contrast, the risk of stroke and myocardial infarction increased linearly with increasing BP. Low BP was associated with all-cause mortality in older adults. The U-shaped association may not be solely attributed to the previously suggested factors, including antihypertensive treatment, potential comorbidities, and functional disability.