The effect of ambient temperature and barometric pressure on ambulatory blood pressure variability.

BACKGROUND The effect of ambient temperature on cardiovascular disease has previously been studied. Less known are the effects of climate on blood pressure (BP) regulation, specifically, the role of temperature on BP variability. METHODS We investigated the effect of temperature and barometric pressure on ambulatory BP variability in 333 men and women with above-optimal BP or stage 1 hypertension participating in the Dietary Approaches to Stop Hypertension (DASH) multicenter feeding trial. Each subject consumed the same diet for 3 weeks. Daytime, nighttime, and 24-h BP were recorded by ambulatory BP monitoring (ABPM). Climatologic data were obtained from local meteorologic centers. RESULTS After adjustment for body mass index (BMI), age, sex, baseline clinic systolic BP, and clinical center, systolic BP variability was inversely associated with 24-h temperature (P =.005) and daytime temperature (P =.006). There was no observed association between BP variability and barometric pressure. There was a significant trend of increasing nighttime systolic BP and diastolic BP with increasing temperature, but these results did not persist after adjustment for confounding variables. CONCLUSIONS During periods of cold weather, an increase in BP variability may complicate the diagnosis and management of hypertension and may contribute to the high cardiovascular mortality observed in the winter.