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A large cross-sectional study published this month in JAMA Network Open found that extreme heat was associated with small, short-term reductions in blood pressure among adults receiving outpatient care. The analysis included 2,554 community health centers across 40 states, examining more than 4.2 million summer encounters from 2019–2023. On days of extreme heat, patients’ recorded adjusted systolic blood pressure was 0.7 mm Hg lower and diastolic blood pressure was 0.3 mm Hg lower than the blood pressure measured during comparable ambulatory encounters on days that were not classified as extreme heat days (and after the researchers adjusted for factors such as age, sex, race and ethnicity, hypertension and medication status, comorbidities, year, geographic region, and time of day). The effect was greater among patients aged 65 years or older, whose systolic and diastolic pressures were lower by 1.1 mm Hg and 0.8 mm Hg, respectively, compared with reductions of 0.6 mm Hg and 0.3 mm Hg among younger adults. Blood pressure reductions were greatest on the day of heat exposure and the following day—ultimately diminishing by day 3. The authors state: “These findings suggest physiologic responses to heat that may be relevant for clinical [blood pressure] measurement and cardiovascular risk assessment in outpatient settings.”
Symptom check: Although the average changes were unlikely to be clinically meaningful for individual patients, according to the authors, patients with symptomatic hypotension, dehydration, or heat-related illness may be more likely to seek urgent or emergency care.
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