Sleep efficiency and nocturnal hemodynamic dipping in young, normotensive adults

Blunted dipping of nocturnal systolic arterial pressure (SAP) and heart rate (HR) are independent risk factors for hypertension and all-cause mortality. While several epidemiological studies report a significant association between short sleep duration and hypertension, associations between sleep efficiency and the nocturnal drop of SAP remain controversial. Moreover, relations between sleep efficiency and HR diurnal patterns have been overlooked. We hypothesized that low sleep efficiency (<85%) would be associated with blunted nocturnal SAP and HR dipping. Twenty-two normotensive subjects (13 men, 9 women; age: 18-28 yr) wore an actigraphy watch for 7 days and nights, and an ambulatory blood pressure monitor for 24 h on a nonactigraph night. There were no differences in age, sex, body mass index, mean sleep time, number of awakenings, or 24-h blood pressure between the low (n = 12) and high (n = 10) sleep efficiency groups. However, the low sleep efficiency subjects demonstrated a blunted dip of nocturnal SAP (10 +/- 1% vs. 14 +/- 1%, P = 0.04) and HR (12 +/- 3% vs. 21 +/- 3%, P = 0.03) compared with the high sleep efficiency group. The low sleep efficiency group also demonstrated a higher mean nocturnal HR (63 +/- 2 vs. 55 +/- 2 beats/min; P = 0.02). These findings support growing evidence that sleep efficiency, independent of total sleep time, may be an important cardiovascular risk factor.