The Riskiest Time for the Brain

Abstract

The natural circadian rhythm of blood pressure (BP) typically includes a nocturnal decrease of 10% to 20% in BP compared with daytime, awake values.1,2 However, in as many as 25% to 35% of hypertensive patients, there is a moderate-to-marked loss of this decline in nocturnal BP, a phenomenon that has been associated with excessive cardiac,3 renal,4 and cerebrovascular5 target organ damage. In addition, patients with hypertension who exhibit a nocturnal BP increase compared with daytime BP (so-called “risers”) have the worst prognosis for future stroke and cardiac events.6 In contrast, there is also some evidence that patients with marked nocturnal BP declines (so-called “extreme dippers”) are at greater risk for ischemic strokes and silent myocardial ischemia than patients whose decline in BP during sleep is normal.7 Both the etiologies and the consequences of an elevated nocturnal BP are diverse. Since Shimada et al8 first reported a study evaluating ambulatory BP monitoring in older patients with hypertension using MRI 15 years ago, there has been an ongoing issue with our general understanding of BP variability and the brain as a target organ, because most studies have had small sample sizes and have been performed in homogenous populations. In this issue of Hypertension , Schwartz et al9 have provided us with a large cross-sectional study from Minnesota and Mississippi of 263 black and 343 white subjects who underwent clinic …