Season of Blood Pressure Measurement Screening and All-Cause Mortality: A Community-Based Prospective Cohort Study.

BACKGROUND The association between season of screening blood pressure (BP) measurement and adverse outcomes has not been examined among populations without prior physician-diagnosed hypertension. We aimed to investigate the association between the season of screening clinic BP measurement and the risk of all-cause mortality. METHODS This was a prospective cohort study, and data were analyzed from an ongoing community hypertension screening program in Shanghai between 2018 and 2024. In this study, 166 670 participants aged 35 to 89 years who were free of prior physician-diagnosed hypertension were included and had their BP measured with an automated office BP platform in Shanghai community health centers. Participants were categorized into 4 groups by season of screening BP measurement: spring, summer, autumn, and winter. Deaths were ascertained from linkage to the Shanghai Vital Statistics Registry with follow-up until September 30, 2024. Cox regression models were used to examine the association between seasons of BP measurement and risk of all-cause mortality. RESULTS During a median follow-up of 1.6 years, 1850 (1.1% of participants) all-cause deaths occurred. The incidence rate of all-cause mortality was 5.0 per 1000 person-years and was higher in participants with screening BP measured in summer (5.4 per 1000 person-years) than in other seasons (4.4, 5.3, and 4.9 per 1000 person-years in spring, autumn, and winter, respectively). After adjustment for age, sex, residential region, and systolic and diastolic BP, the hazard ratio for the risk of all-cause mortality in participants with screening BP measured in summer relative to the overall population was 1.14 (95% CI, 1.05-1.24). There was no any significant interaction between the season of screening BP measurement and sex, age, and hypertension status in relation to the risk of all-cause mortality (all P≥0.05). CONCLUSIONS Screening for raised BP in summer was associated with significantly higher risks of all-cause mortality, though the mean systolic/diastolic BP was lowest in summer. The findings imply that if only clinic BP is measured for hypertension screening in 4-season countries and regions, repeated BP measurements, preferably in different seasons, might be needed.