Sleep, slow-wave sleep, and blood pressure.

There is increasing evidence that alterations in sleep continuity due to central nervous system arousal and/or reductions in deeper stages of sleep adversely affect blood pressure and contribute to hypertension. Disturbed sleep also blunts the normal nocturnal dip in blood pressure and may lead to sustained daytime hypertension as well. Nocturnal drops in blood pressure result from increased parasympathetic and reduced sympathetic activity during sleep. Slow-wave sleep, considered to be the most "restorative," is the specific sleep state associated with the largest decline in sympathetic activity. The time in slow-wave sleep declines with age as well as in association with other health problems. A reduction in the time in slow-wave sleep has recently been reported to predict increased incident hypertension. The mechanisms by which this occurs have not been well described but may include alterations in dipping patterns, sympathetic nervous system activity, corticotrophin pathways, and the renin-angiotensin system. This article reviews the overall association between sleep and hypertension, with a specific focus on slow-wave sleep, a possible novel target for future blood pressure interventions.