Nocturnal sleep and blood pressure in essential hypertension.

Blood pressure and sleep-wakefulness patterns were monitored in the sleep laboratory over four consecutive nights in six patients with mild hypertension and six age- and sex-matched controls. In both hypertensives and normals, blood pressure levels decreased during sleep compared with presleep levels by 16.6 and 8.4%, respectively; levels for hypertensives, however, remained significantly above those for the normals. The nocturnal drop in blood pressure for both groups appeared to be related primarily to the general state of sleep rather than to any specific sleep stage. Nocturnal patterns of sleep stages and sleep cycling were almost identical for the two groups. Nocturnal blood pressure fluctuation was correlated positively with the distribution of nocturnal wakefulness in hypertensives but not in normotensives. This suggests that with hypertension there is some diminution of the dampening effect of sleep itself upon blood pressure which normally carries over into periods of nocturnal wakefulness. This alteration in patients with mild hypertension may reflect a decrease in the sensitivity of the baroreceptor reflex or some other pathophysiological process.