Attending to the effects of outdoor temperature on blood pressure: multicenter study based on ambulatory monitoring

Abstract

Sudden fluctuations in blood pressure (BP) over a short period may trigger cardiovascular events, and outdoor temperature may be a risk factor. There is a lack of conclusive observational evidence linked hourly temperature with ambulatory BP indicators. We aimed to explore the effects of hourly outdoor temperature on ambulatory BP, BP variability and load. A large-scale, multicenter study among 31,838 adults from 7 Chinese cities was conducted between March, 2016 and November, 2020. Hourly temperature was obtained from the nearest weather stations. We collected ambulatory systolic (SBP), diastolic blood pressure (DBP), the BP variability and load of the day, and used linear mixed-effect model combined with distributed lag models to analyze data. Outdoor temperature was inversely associated with most ambulatory BP indicators. The effects of low temperature on BP appeared and peaked at the concurrent hour, then gradually attenuated and disappeared around at lag 20h. Compared to the referent temperature (P₉₉), exposure to low temperature (P₁) was associated with cumulative increments (over lag 0 to 20 h) of 9.71 mmHg, 4.85 mmHg and 20.58 mmHg for 24-hour, nighttime and morning SBP, respectively, as well as 8.71 mmHg, 4.72 mmHg and 14.32 mmHg for 24-hour, nighttime and morning DBP. Furthermore, there were significant associations between decreasing temperature and increased BP variability and load at lag 0 d. Our study provides compelling evidence that low temperature can elevate BP-related indicators, underscoring the necessity of flexible treatment strategies and targeted public health interventions, especially for susceptible populations during the cold season.