News Author: Laurie Barclay, MD

April 6, 2006 — Sleeping less than 6 hours per night increases the risk for hypertension, according to the results of a longitudinal study reported in the April 3 Online First issue of Hypertension.

"Depriving healthy subjects of sleep has been shown to acutely increase blood pressure and sympathetic nervous system activity," write James E. Gangwisch, MD, from the College of Physicians and Surgeons at Columbia University in New York, NY, and colleagues. "Prolonged short sleep durations could lead to hypertension through extended exposure to raised 24-hour blood pressure and heart rate, elevated sympathetic nervous system activity, and increased salt retention. Such forces could lead to structural adaptations and the entrainment of the cardiovascular system to operate at an elevated pressure equilibrium."

The investigators conducted longitudinal analyses of the first National Health and Nutrition Examination Survey (n = 4810), using Cox proportional hazards models and controlling for covariates. During the 8- to 10-year follow-up period between 1982 and 1992, there were 647 cases of hypertension, determined by physician diagnosis, hospital record, or cause of death.

In subjects between the ages of 32 and 59 years, sleep durations of less than 6 hours per night were associated with more than double the risk for hypertension (hazard ratio, 2.10; 95% confidence interval [CI], 1.58 - 2.79). Controlling for potential confounding variables only partially reduced this relationship. The increased risk continued to be significant after controlling for obesity and diabetes, consistent with the hypothesis that these variables would act as partial mediators.

"Short sleep duration could, therefore, be a significant risk factor for hypertension," the authors write. "Further research is needed to investigate the biological mechanisms that link short sleep duration and high blood pressure. If short sleep duration functions to increase blood pressure, then interventions that increase the amount and quality of sleep could potentially serve as treatments and as primary preventative measures for hypertension."

Study limitations include relatively low sample size for older subjects; inability to determine whether short self-reported sleep durations indicated sleep deprivation or normal variability between individuals in required sleep durations; inability to rule out reverse causation or uncontrolled confounders; use of self-reported sleep durations; lack of repeated measures of sleep duration; possible underdiagnosis of hypertension; possible bias arising from loss to follow-up; and missing data on baseline risk variables.

"In results from the National Sleep Foundation 2002 Sleep in America Poll, not getting enough sleep was associated with irritability, impatience, pessimism, and feeling tired and stressed," the authors point out. "It would seem that these feelings and emotional states would function to lessen one's resolve and willpower to follow dietary or exercise regimens that would be protective against hypertension."