Seasonal variations of blood pressure in adults: Tehran lipid and glucose study.

There is no comprehensive report on seasonal variations in individuals' blood pressure (BP) in Iranian subjects. The aim of this study is to evaluate individuals' BP during the four seasons of the year in a large number of adults in Tehran. In a population-based study in Tehran, over a period of ten years (from 1998 to 2011) during the follow up of the four phases of the TLGS, data from a total of 29777 participants aged 20-80 years (42.29% male and 57.71% female) were collected. The participants' systolic and diastolic BP (SBP and DBP) were measured in every season, and adjusted for weight, age, sex, body mass index, and ambient temperature, history of diabetes mellitus and anti-hypertensive drugs, and their mean SBPs and DBPs were compared. Mean SBP and DBP was 116.79 and 75.29 in spring, 116.11 and 74.81 in summer, 117.45 and 75.95 in fall and 119.03 and 76.28 mmHg in winter. There was a statistically significant difference between mean SBP in summer and winter (P < 0.010). The difference between mean SBP in winter and spring and the difference of mean DBP in winter and summer were near significance level (P = 0.058 and 0.086, respectively). Compared to summer and spring, the individuals' SBP was higher during winter and their DBP in winter was also higher compared to summer. More attention should be paid to BP measurement in epidemiological studies.