The seasonal changes of office and ambulatory blood pressure (BP) in hypertensive patients are well-known. At the same time, the information concerning seasonal changes of 24-hour characteristics of BP profile is limited. The investigation of BP variability (BPV) is important due to its independent prognostic role and association with neural and humoral mechanisms of BP regulation. The aim of the study was to assess the dynamics of 24-hour BPV (winter vs. summer) in two sites of the Russian Federation – Ivanovo (relative north) and Saratov (relative south).Design and method:
We included patients from the general population who visited ambulatory clinics for various reasons. The main inclusion criterion was office BP 130/85–139/89 mmHg or long-term antihypertensive therapy. The ambulatory blood pressure monitoring (ABPM) was performed with the BPLab device twice in each patient: in winter (December-February 2012–2014) and in summer (June-August 2012–2014). The interval between ABPMs was 6 months ± 7 days. The selection criterion for ABPM records was the quality adequate for sophisticated analyses: duration>23.5 hours, absence of data gaps>1 hour, >55 readings per 24 hours. BPV was calculated as day and night SD and ARV24. The data analysis was adjusted for age, sex, treatment status and average BP.Results:
1766 patients were enrolled, and 782 of them completed both visits - 513 from Ivanovo (mean age 52 ± 10 years, 185 men), and 269 from Saratov (mean age 54 ± 11 years, 151 men). We found no seasonal changes of BPV in Saratov. BPV in Ivanovo was higher in winter than in summer (mean ARV24 of systolic BP (SBP) 10.0 ± 1.3 vs. 9.8 ± 1.3 respectively, p < 0.05). We found a substantial difference in BPV between sites: mean ARV24 of SBP in winter was 9.8 ± 1.3 in Ivanovo and 10.6 ± 1.4 in Saratov, in summer – 9.6 ± 1.3 and 10.5 ± 1.4 respectively, p < 0.0001.Conclusions:
The higher BPV levels in winter in Ivanovo could reflect insufficient BP control in the cohort with tendency to masked hypertension. The difference in BPV between sites may be explained, among other reasons, by specific kind of continental climate in Saratov. ARV24 appears to be a promising method of BPV assessment.