Prehypertension, the Elderly, Dementia, and Sleep -- How to Treat the Blood Pressure?

Linda Brookes, MSc


April 21, 2006

In This Article

Lack of Sleep Linked to Increased Risk of High Blood Pressure

People who average ≤ 5 hours of sleep a night are at increased risk of developing hypertension, according to research reported in Hypertension.[14] However, there is apparently no such association between short sleep duration and hypertension in people aged ≥ 60 years. Depriving healthy subjects of sleep has been shownto acutely increase blood pressure and sympathetic nervous systemactivity, and sleep disorders have been linked with cardiovascular disease, but this is believed to be the first time that short sleep duration has been associated with the development of hypertension in people without sleep disorders.

In a study supported by the National Institute of Mental Health, researchers from the United States, The Netherlands, and Mexico analyzed data from the epidemiologic follow-up studies of the first National Health and Nutrition Examination Study (NHANES I). The analysis was based on NHANES I data from 4810 people aged 32-86 who did not have hypertension at baseline. The 1982-84 follow-up survey asked participants how many hours they slept at night. This survey also asked about history of diabetes, age, physical activity, alcohol consumption, salt consumption, pulse rate, daytime sleepiness, depression, smoking, education, ethnicity, and gender. Depressive symptoms were also assessed.

During 8-10 years of follow-up, 647 of the 4810 participants were diagnosed with hypertension (> 140/90 mm Hg), 472 cases in subjects aged 32-59 years and 175 in subjects aged 60-86 years. Of the younger people aged 32-59 years who slept for ≤ 5 hours a night, 23.6% developed hypertension compared with 11.8% of those who got 7-8 hours of sleep. Subjects who slept ≤5 hours per night continued to be significantly more likely to be diagnosed with hypertension after controlling for factors such as obesity, diabetes, physical activity, salt and alcohol consumption, smoking, depression, age, education, gender, and ethnicity. However, among people aged 60-86 years, the incidence of hypertension was the same -- 14% -- in those who slept for ≤ 5 hours and those who slept for 7-8 hours.

Lead author James E Gangwisch, PhD (Columbia University, New York, NY), said that the differences between the younger and older subjects might be explained by the fact that advanced age is associated with difficulties falling and staying asleep. Another factor could be that subjects suffering from hypertension, diabetes, and obesity would be less likely to survive into their later years. Sleep durations of ≤ 5 hours were associated with older age, higher body mass index (BMI), lower physical activity, lower alcohol consumption, higher pulse rate, depression, daytime sleepiness, nonwhite ethnicity, and education level lower than a high school graduate.

Among study limitations, the researchers noted that hypertension often goes undetected. An analysis of NHANES III data showed that over 30% of people who had hypertension were unaware that they had the condition. In NHANES I analysis, patients with short sleep duration were not known to be more or less likely to seek or receive treatment and therefore be diagnosed with hypertension.

Since the study was based on observational data, more research is needed to confirm the association between short sleep duration and high blood pressure, say Dr Gangwisch and his colleagues. "We need to investigate the biological mechanisms and, if confirmed, design interventions that will help people modify sleep behavior." Prolonged short sleep durations could lead to hypertensionthrough extended exposure to raised 24-hour blood pressure andheart rate, elevated sympathetic nervous system activity, andincreased salt retention. Such forces could lead to structuraladaptations and the entrainment of the cardiovascular systemto operate at an elevated pressure equilibrium. If short sleep duration is confirmed as raising blood pressure, then "interventions that increase and improve the quality of sleep could potentially serve as treatments and as primary preventative measures for hypertension," the researchers suggest.

One potential mechanism linking short sleep duration to hypertension, as suggested by Brent M Egan, MD (Medical University of South Carolina, Charleston), in an accompanying editorial, is "an increased blood pressure load resulting from prolongation of higher blood pressure while awake and truncation of the blood pressure dip characteristic of sleep."[15] "A decrease in sleep duration leads to both greater blood pressure load and prolonged exposure to an activated sympathetic nervous system, which could accentuate structural remodeling and augment renal sodium retention," says Dr Egan. "Structural changes in key target organs participating in blood pressure regulation including the kidney, heart, and vasculature could serve to perpetuate and accelerate age-related increases in blood pressure, especially in those at risk."

Dr. Egan stresses the public health significance of the study's findings, noting that the average sleep time in the United States has fallen dramatically during the past century, from 9.0 hours in 1910 to 7.5 hours in 1975 and 6.8 hours in 2005. In 2005, 16% of adults in the United States reported that they got < 6 hours of sleep per night. "Short sleep duration is a risk marker and a plausible risk factor for future hypertension in addition to insulin resistance, obesity, and diabetes. Americans are attempting to fit ever more into 24 hours, and many appear willing to 'burn the candle at both ends' to accomplish that objective," Dr. Egan says. "The emerging picture suggests that a growing proportion of Americans is at increased risk for hypertension and other features of the metabolic syndrome based on short sleep duration. Of concern, many adults believe that < 6 hours of sleep allows them to function optimally, and an even larger proportion indicates they are already sleeping too much. Thus, sleep duration is likely to continue its downward trend. . ., which could continue to fuel the epidemic of metabolic-syndrome-related risk and disease." Public health messages to emphasize the health benefits of adequate (≥6 hours) sleep and the risks of short sleep duration may be useful, Dr Egan suggests. Future studies should investigate whether prescription medications will ameliorate health risks related to short sleep duration among insomniacs, he proposes.


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