SEASONAL BLOOD PRESSURE VARIATION ASSESSED BY DIFFERENT MEASUREMENT METHODS

Abstract

Objective: Seasonal changes in blood pressure (BP) in response to changes in environmental temperature appear to be a common and global phenomenon. This study aimed to review the published evidence on the seasonal changes in BP assessed using different measurement methods. Design and method: A systematic PubMed search was performed for studies assessing seasonal changes in office (OBP), home (HBP) and ambulatory BP (ABP). Prospective and cross-sectional studies were included fulfilling the following criteria: (i) report of ambulatory and/or home BP data; (ii) sample size >1,000 for studies reporting only OBP data. Results: Among 596 initially retrieved studies, 47 fulfilled the criteria and were included (856,539 participants, weighted age 49.7 ± 4.8 years, 42.7% treated for hypertension). Random effects meta-analysis of these studies showed that summer minus winter systolic/diastolic BP differences (pooled estimate with 95% confidence intervals) were: OBP (27 studies) −5.8 (−7.5, −4.2)/−3.4 (−4.1, −2.7) mmHg; daytime ABP (15 studies) −3.4 (−4.4, −2.4)/−2.1 (−2.8, −1.4) mmHg; night-time ABP 1.3 (0.2, 2.3)/0.5 (−0.2, 1.2); HBP (9 studies) −6.1 (−7, −5.1)/−3.1 (−3.5, −2.6) mmHg. 28 of these studies (N = 5,278) were prospective and examined the same individuals during different seasons. Sensitivity analyses including only the 28 prospective studies provided similar findings with seasonal systolic/diastolic BP difference: OBP −6.4/−4.2 mmHg; daytime ABP −3.9/−2.7 mmHg, nighttime ABP 0.5/−0.5 mmHg, HBP −6.4/−3.3 mmHg. Meta-regression analysis of prospective studies showed that seasonal systolic daytime ABP difference was related to the percentage of treated hypertensives across studies (p = 0.02) and borderline to age (p = 0.06), whereas gender, body mass index, summer temperature, seasonal difference in temperature, and winter BP levels had no significant effect (p = NS). Conclusions: The current evidence indicates that seasonal BP changes are evident in all measurement methods except for nighttime ABP, with average BP decline in summer at about 5/3 (systolic/diastolic) mmHg. The seasonal BP changes appear to be larger in older subjects and in treated hypertensives.