LONG SLEEP DURATION AND AMBULATORY BLOOD PRESSURE

Abstract

Objective: Studies show a link between short sleep duration and hypertension. The mechanistic associations between sleep duration and blood pressure (BP) are less clear. We studied the association between sleep duration, blood pressure, metabolic profile as well as obstructive sleep apnoea in participants with suspected or confirmed hypertension undergoing 24 h ambulatory blood pressure measurement (ABPM). Design and method: We included 177 participants (mean age 57 ± 11 years, 67 women) referred for ABPM, with available exact time-points for bedtimes during the recording. Daytime and night-time BP values were calculated accordingly. Biochemistry included triglycerides (TG), high- and low-density lipoproteins (HDL, LDL) and total cholesterol. The HDL/TG ratio was calculated as a marker of glucose intolerance. Sleep apnoea was quantified by simultaneous ambulatory polygraphy. Results: Participants were stratified into those with short (n = 16) /normal (n = 139) /long (n = 22) sleep (< = 6 h, > 6 < = 9 h and > 9 h). There were no differences in age, body mass index (BMI) or apnoea hypopnea index (AHI) between groups. Mean office BP was 146 ± 19/89 ± 11 mmHg and mean 24 h ABPM 133 ± 14/80 ± 8 mmHg. By standard ABPM definitions 81, 86, and 77% in the short/normal/long sleep group were hypertensive, and 56, 56 and 73% were on antihypertensive medication. The long sleep group had lower 24 h diastolic BP than the short and normal sleep groups (p < 0.05 by ANOVA). TG levels and TG/HDL ratio were higher in the long sleep group than in the short sleep group (both p < 0.05 by ANOVA; not adjusted for statin treatment). No differences were found in HDL, LDL, or total cholesterol between groups. In a multiple linear regression model, longer sleep duration, older age, and female sex were all independently associated with lower 24 h ABPM diastolic BP (all p < 0.01; full model R2 = 0.25, p < 0.001) while BMI, AHI, TG, and the TG/HDL ratio were not related. Conclusions: Longer sleep duration was independently associated with lower ABPM 24 h diastolic BP together with older age and female sex. The observation with increased TG and TG/HDL ratio in the long sleep group warrants further study.