Short-Term Effects of Personal-Level Environmental Temperature on Ambulatory Blood Pressure in Patients With Hypertension: A Multicity Panel Study.

BACKGROUND: The inverse association between blood pressure (BP) and ambient temperature is known, but evidence on personal-level environmental temperature (PET) and ambulatory BP among patients with hypertension remains limited. METHODS: This 3-phase panel study recruited 277 patients with hypertension with intermediate-to-high cardiovascular disease risk in 4 cities in China from November 2017 to August 2019. Continuous PET and ambulatory BP were recorded by personal portable monitors. We used generalized linear mixed-effect models to explore the associations of 24-hour daytime and nighttime ambulatory BP, BP variability, and circadian rhythm with PET. Generalized additive mixed models were used to fit the exposure-response curves. Subgroup analyses were stratified by BP control status, body mass index, age, and sex. RESULTS: An acute, inverse, and near-linear association of PET with ambulatory BP, especially daytime systolic BP, were observed, with a 0.61 (95% CI, 0.48-0.75) mm Hg increase per 1 °C decrease of PET on the concurrent day. BP variability was linearly correlated with PET decline across all exposure windows. Circadian indicators, including morning BP, morning BP surge, and nocturnal BP decline, were also significantly associated with PET. Stronger associations were found among women and those with uncontrolled BP. Particularly, per 1 °C decline in PET on the concurrent day resulted in elevated daytime systolic BP of 0.98 (95% CI, 0.67-1.29) mm Hg, 0.43 (95% CI, 0.30-0.56) mm Hg among those with uncontrolled and controlled BP, respectively (P for interaction=0.001). CONCLUSIONS: A decrease in short-term PET exposure could lead to adverse impacts on ambulatory BP indicators. This study highlights the beneficial role of BP control in response to temperature decline in hypertension management.