Sleep fragmentation, awake blood pressure, and sleep-disordered breathing in a population-based study

Arousal from sleep produces transient increases in systemic blood pressure, leading to the suggestion that repeated arousals are associated with a sus tained increase in daytime blood pressure. Using data from the Wisconsin Sl eep Cohort Study, a population-based study, we tested the hypothesis that s leep fragmentation is associated with elevated awake blood pressure. Sleep, breathing, and seated blood pressure measurements from 1,021 participants (age 42 +/- 8 yr; 590 males) were analyzed. Sleep fragmentation was defined as the total number of awakenings and shifts to Stage 1 sleep divided by t he total sleep time (sleep fragmentation index: SFI). To reduce the confoun ding influence of sleep-disordered breathing, which is related to both incr eased daytime blood pressure and sleep fragmentation, all participants with an apnea-hypopnea index (AHI) greater than or equal to 1 were analyzed sep arately. Accounting for the influences of sex, age, body mass index, and an tihypertensive medication use, the SFI was significantly associated with hi gher levels of awake systolic blood pressure in people with an AHI < 1; a 2 standard deviation increase in the SFI was associated with a 3.1 mm Hg ris e in awake systolic: blood pressure. in participants with an AHI <greater t han or equal to> 1, there was no independent association between the SFI an d awake blood pressure after controlling for the influence of the AHI.