Obesity Increases Blood Pressure Variability during the Night

ABSTRACT

BACKGROUND: Previous studies have reported that obesity increases heart rate variability. Body mass index (BMI) has been reported to affect blood pressure variability (BPV) over 24 hours. However, the diurnal variation in the effect of BMI on BPV has not been evaluated. This study aimed to clarify the diurnal variation in the effect of BMI on BPV. METHODS: A total of 2,044 patients were consecutively enrolled in this study, and the data were analyzed retrospectively. All patients underwent 24-hour ambulatory blood pressure monitoring. We divided patients into two groups according to BMI (non-obese group: n = 1,145, BMI or = 25). We compared BPV during daytime and nighttime between the non-obese and obese groups. We also evaluated the impact of BMI on BPV by multivariate regression analysis. RESULTS: On univariate regression analysis, there was no significant difference in BPV during daytime (systolic BP [SBP] variability: 20.7 vs. 21.7, p = 0.511; diastolic BP [DBP] variability: 16.8 vs. 17.5, p = 0.539). However, both SBP variability (13.8 vs. 17.6, p = 0.009) and DBP variability (11.7 vs. 14.3, p = 0.042) during nighttime were affected significantly by BMI. After adjusting other compounding variables (age > 60 years, current smoking habit, hypertension, diabetes mellitus, and use of calcium channel blockers and renin-angiotensin-aldosterone system blockers), multivariate analysis showed that BMI was an independent factor associated with increase in BPV during the night (SBP variability: p = 0.039; DBP variability: p = 0.034). CONCLUSIONS: Obesity increased BPV during nighttime.