Seasonal variation in 24 h blood pressure profile in healthy adults- A prospective observational study.

The clinical and experimental data on seasonal variation in blood pressure is mainly from office and home blood pressure (BP) monitoring studies. There are few studies from temperate climates on seasonal changes with ambulatory blood pressure (ABP) monitoring and none from India. This is a prospective, observational study among healthy adults. ABP was measured in four different seasons in 28 subjects. Mean arterial pressure (MAP), ambulatory systolic blood pressure (SBP), and ambulatory diastolic blood pressure (DBP) were significantly higher in winter compared to summer season. 24-hour MAP was lowest in summer while highest MAP was recorded in winter (97.04 ± 8.30 and 103.89 ± 8.54, respectively). The mean difference was -6.86 mm Hg (95% CI: -10.74 to -2.97, p = 0.001). This difference was mainly due to increase in day time MAP. There was no difference in 24 h systolic and diastolic blood pressure between summer and winter. There was significant difference between summer and winter in the SBP (day time) [125.61 ± 11.44 and 131.93 ± 9.46, mean difference -6.32 (95% CI: -10.69 to -1.95, p = 0.005)] and DBP (day time) [79.57 ± 9.95 and 87.07 ± 9.9, mean difference -7.50 (95% CI: -12.49 to -2.51, p = 0.003)]. The night time systolic and diastolic BP was similar during winter and summer. Thus, BP increases significantly during winter compared to summer season. This change is primarily in the day time systolic, diastolic and mean blood pressures. Larger studies are required to further validate our findings.