INVERSE SEASONAL VARIATIONS OF AMBULATORY BLOOD PRESSURE ARE ASSOCIATED WITH CARDIOVASCULAR OUTCOMES IN HYPERTENSIVE PATIENTS

Abstract

Objective: The seasonal changes of blood pressure (BP) in hypertensive patients have been widely investigated and attracted an increasing scientific interest during the past two decades. However, it is unclear whether these BP variations are related to cardiovascular risk. Design and method: We included patients aged 40–79 years who visited ambulatory clinics for various reasons. The main inclusion criteria were office BP 130/85-139/89 mm Hg, hypertension stage 1, or long-term antihypertensive therapy. The ambulatory blood pressure monitoring (ABPM) was performed with the BPLab device (Nizhny Novgorod, Russia), twice in all patients: in winter (December-February 2012–2014) and in summer (June-August 2012–2014). The interval between ABPMs was 6 months ± 7 days. The selection criteria for ABPM records were: duration >23.5 hours, absence of data gaps >1 hour, and >55 readings per 24 hours. We analyzed the individual ambulatory and office seasonal BP differences in each patient. The participants were followed up until October 31st 2019 (mean follow-up 76.8 ± 5.1 months). The composite primary endpoint included death, myocardial infarction, stroke, transient ischemic attack, angina pectoris, and development of heart failure. The preliminary analyses included ANOVA, sensitivity analysis, and descriptive statistics. Results: 770 patients completed both visits. The outcome information was available in 528 patients: 335 from Ivanovo and 193 from Saratov (mean age 55 ± 10 years, 220 men). The endpoints were registered in 50 patients. We found the inverse mean winter-summer BP difference in the group of patients with cardiovascular outcomes (see table). In contrast, this difference was positive in the other group (see table). The sensitivity analysis (the winter-summer BP difference classified into 4 groups: inverse (<0), small (0–5 mm Hg), medium (5–10 mm Hg), and large (>10 mm Hg) variation) confirmed the hypothesis for 24-hour diastolic BP. We found no significant associations for office BP. Conclusions: The inverse seasonal BP variability may be associated with a higher risk of cardiovascular events; compared to patients with standard BP variability (BP is higher in winter, than in summer). Our data provide the tentative argument in favor of additional ambulatory BP control. The problem of seasonal BP variability warrants further investigation.