Research Ties Lack of Sleep To Risk for Hypertension
By NICHOLAS BAKALAR
Published: April 18, 2006
Getting too little sleep may be a significant risk factor for high blood pressure.
In a study of more than 4,800 men and women, people ages 32 to 59 who got five hours of sleep a night or less were about 60 percent more likely to develop hypertension than those who slept six to eight hours.
The trend was the same even after controlling for depression, alcohol consumption, smoking, pulse rate, obesity, diabetes and other variables.
The study appeared this month in the Online-First issue of the journal Hypertension.
Researchers used data from a large epidemiological study, following subjects over a 10-year period. The participants had standardized medical examinations and answered questions about their health habits, including sleep patterns. The scientists excluded from the analysis anyone who already had hypertension, and over the next 8 to 10 years, they recorded the incidence of newly diagnosed cases of high blood pressure, or in a few cases, the cause of death.
''It's been known for a long time that sleep disorders are associated with hypertension,'' said James E. Gangwisch, the lead author of the study and a postdoctoral fellow at Columbia's Mailman School of Public Health, ''but that could be for reasons besides not getting enough sleep. This is the first study that shows a relationship between short sleep duration itself and high blood pressure.''
The researchers did not find the connection between sleep deprivation and hypertension in the older group of subjects, those 60 to 86. The authors suggest that this may be because people with hypertension, obesity and diabetes are less likely to survive into their later years, or because lack of sleep in younger people is more closely associated with obesity than it is in those over 60.
Dr. Meir Stampfer, chairman of the department of epidemiology at the Harvard School of Public Health, said that the findings were of moderate interest.
''This study suggests that sleep duration may contribute to hypertension,'' Dr. Stampfer said, ''but the magnitude of the association is modest compared to dietary factors,'' especially being overweight, ''the main driver for hypertension.'' He was not involved in the study.
Getting more than the average amount of sleep had no effect, either protective or helpful. People who got nine or more hours of sleep were no less likely to have high blood pressure than those who slept six to eight hours.
While many factors contribute to high blood pressure, lack of sleep appears to be an independent cause, according to Dr. Dolores Malaspina, a co-author of the paper.
''Normally during sleep our heart rate and blood pressure are lower,'' Dr. Malaspina explained. ''In people deprived of sleep over a long period of time the average work done by the heart increases, and that can lead to irreversible changes in the heart and blood vessels.'' Dr. Malaspina is a professor of clinical psychiatry at Columbia.
Lack of sleep may also increase the effect of other hypertension risk factors, the authors suggest. It is probable, they write, that short sleep duration leads to obesity by influencing insulin sensitivity and the enzymes that control appetite.
Short sleep duration is associated with irritability, impatience, pessimism and stress -- factors that may reduce the ability to follow healthy diet and exercise regimens.
The researchers concede that the study has certain weaknesses. The sleep duration figures depend on self-reports -- not always reliable. And, the scientists were unable to rule out the possibility that lack of sleep was itself an early symptom of hypertension that was diagnosed later.
Because hypertension often goes undiagnosed, the scientists had no way of knowing whether sleep-deprived participants were more or less likely to seek treatment and get a diagnosis than those with normal sleep patterns.
Analysis of data from another large epidemiological study cited in the paper found that 30 percent of people with high blood pressure were unaware they had it.