[Age and gender difference in circadian rhythm in blood pressure]

In order to evaluate the effect of gender and aging on the diurnal rhythm of blood pressure (BP), we performed ambulatory BP monitoring in 267 normotensive volunteers (mean age +/- SD 52.1 +/- 24.6 years, range 16-93 years, 114 men, 153 women). Ambulatory 24-hour BP was recorded every 30 minutes with an oscillometric method by ABPM630 (Nippon-Kolin, Japan). Circadian rhythm was determined by fitting the 24-hour cosine function curve. Subjects were divided into three age groups, consisting of the Y group (age < 30), M group (age > or = 30 but < 60), and E group (age > or = 60). Highest normal values of the 24-hour mean BP (90 percentile of the values) were 126/75 mmHg in the Y group, 126/76 mmHg in the M group, and 154/85 mmHg in the E group in men. They were 117/67 mmHg, 125/77 mmHg 151/79 mmHg respectively in women. The MESOR of SBP increased with age in women, though it was significantly higher only in the E group among men. The amplitude of SBP decreased with age significantly only in men. The acrophase of SBP shifted to an earlier time of day with aging in both men and women. The trends in the circadian rhythm of DBP with age were similar to those of SBP. In conclusion, the circadian rhythm of blood pressure varies with gender and aging. The 24-hour blood pressure values should be considered with evaluating sex-age matched reference values.