Determinants of exaggerated difference in morning and evening home blood pressure in Japanese normotensives

The aim of this study was to evaluate factors contributing to morning-evening difference in systolic blood pressure (SBP) in Japanese normotensive subjects. A total of 605 Japanese subjects (393 men and 212 women; mean age, 38.7 years) receiving no antihypertensive agents and without diagnosed hypertension (≥140/90 mm Hg) were studied using self-measured home BP monitoring. Triplicate morning and evening measurements were performed on 7 consecutive days. The mean of the second and third measurements, as well as the mean of measurements on days 2-7 were adopted as an individuals' home BP value. The morning-evening difference in SBP ranged from -24.8 to 34.8 mm Hg. The highest quartile (Q4) group of the morning-evening difference (≥4.3 mm Hg, n=151) comprised an older age (43.6±10.2 vs. 37.1±9.8 years, P<0.01) and a higher prevalence rate of men (72.8 vs. 62.3%, P<0.05), regular alcohol drinkers (45.0 vs. 24.9%, P<0.01) and measurement after bathing at night (50.3 vs. 35.2%, P<0.01) than did the other quartile groups (Q1-Q3, n=454). In multiple logistic regression analysis, independent risk factors for the Q4 group were older age (10 years older: odds ratio (OR) 1.67, P<0.01, 95% confidence interval (CI): 1.37-2.04), regular alcohol drinking (OR 1.98, P<0.01, CI: 1.28-3.07) and post-bathing measurement at night (OR 1.97, P<0.01, CI: 1.30-2.97). In conclusion, older age, regular alcohol drinking and post-bathing measurement at night were significant determinants of an exaggerated morning-evening difference in SBP in Japanese normotensives.