If you're middle age and sleep five or less hours a night, you may be increasing your risk of developing high blood pressure, according to a study released by Columbia University's Mailman School of Public Health and the College of Physicians and Surgeons, and reported in Hypertension: Journal of the American Heart Association.
"Sleep allows the heart to slow down and blood pressure to drop for a significant part of the day," said James E. Gangwisch, PhD, lead author of the study and post-doctoral fellow in the psychiatric epidemiology training (PET) program at the Mailman School. "However, people who sleep for only short durations raise their average 24-hour blood pressure and heart rate. This may set up the cardiovascular system to operate at an elevated pressure."
Dr. Gangwisch said that 24 percent of people ages 32 to 59 who slept for five or fewer hours a night developed hypertension versus 12 percent of those who got seven or eight hours of sleep. Subjects who slept five or fewer 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.
The researchers conducted a longitudinal analysis of data from the Epidemiologic Follow-up Studies of the first National Health and Nutrition Examination Study (NHANES I). The analysis is based on NHANES I data from 4,810 people ages 32 to 86 who did not have high blood pressure at baseline. The 1982-84 follow-up survey asked participants how many hours they slept at night. During eight to 10 years of follow-up, 647 of the 4,810 participants were diagnosed with hypertension. Compared to people who slept seven or eight hours a night, people who slept five or fewer hours a night also exercised less and were more likely to have a higher body mass index. (BMI is a measurement used to assess body fatness). They were also more likely to have diabetes and depression, and to report daytime sleepiness.
"We had hypothesized that both BMI and a history of diabetes would mediate the relationship between sleep and blood pressure, and the results were consistent with this," Dr. Gangwisch said.
Sleep deprivation has been shown previously to increase appetite and compromise insulin sensitivity.
Short sleep duration was linked to a new diagnosis of high blood pressure among middle-aged participants, but the association was not observed among people age 60 or older, he said. Dr. Gangwisch said 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.
Among study limitations, researchers found that high blood pressure often goes undetected. An analysis of NHANES III data showed that over 30 percent of people who had high blood pressure didn't know they had it.
Since the study is based on observational data, Dr. Gangwisch said more research is needed to confirm the association between short sleep duration and high blood pressure. "We need to investigate the biological mechanisms and, if confirmed, design interventions that will help people modify sleep behavior," he said.
Dr. Gangwisch said the study's main message is clear: "A good night's sleep is very important for good health."
Co-authors of the study include Andrew G. Rundle, DrPH, assistant professor of Epidemiology at the Mailman School of Public Health; and Columbia University Medical Center's Steven B. Heymsfield, MD; Bernadette Boden-Albala, DrPH; Ruud M. Buijs, PhD; Felix Kreier, PhD; Thomas G. Pickering, MD, DPhil; Gary K. Zammit, PhD; and Dolores Malaspina, MD. Support for the study was provided by a National Research Service Award by the National Institute of Mental Health.
Women weight gain
Women who sleep 5 hours or less per night weigh more on average than those who sleep 7 hours, according to a study to be presented at the American Thoracic Society International Conference on May 23rd.
The study found that women who slept for 5 hours per night were 32% more likely to experience major weight gain (defined as an increase of 33 pounds or more) and 15% more likely to become obese over the course of the 16-year study compared with women who slept 7 hours. Women who slept for 6 hours were 12% more likely to have major weight gain and 6% more likely to become obese compared with women who slept 7 hours a night.
The study included 68,183 middle-aged women who were enrolled in the Nurses Health Study. They were asked in 1986 about their typical night's sleep, and were then asked to report their weight every 2 years for 16 years.
On average, women who slept 5 hours or less per night weighed 5.4 pounds more at the beginning of the study than those sleeping 7 hours and gained an additional 1.6 pounds more over the next 10 years.
"That may not sound like much, but it is an average amount--some women gained much more than that, and even a small difference in weight can increase a person's risk of health problems such as diabetes and hypertension," said lead researcher Sanjay Patel, M.D., Assistant Professor of Medicine at Case Western Reserve University in Cleveland, OH.
Dr. Patel noted that this is by far the largest study to track the effect of sleep habits on weight gain over time. "There have been a number of studies that have shown that at one point in time, people who sleep less weigh more, but this is one of the first studies to show reduced sleep increases the risk of gaining weight over time."
The researchers looked at the women's diets and exercise habits to see if they could account for part of the findings. "Prior studies have shown that after just a few days of sleep restriction, the hormones that control appetite cause people to become hungrier, so we thought that women who slept less might eat more. But in fact they ate less," Dr. Patel said. "That suggests that appetite and diet are not accounting for the weight gain in women who sleep less."
The researchers also asked women about how much they participated in exercise activities such as running, jogging or playing tennis. But they didn't find any differences in physical activity that could explain why women who slept less weighed more.
"We don't have an answer from this study about why reduced sleep causes weight gain, but there are some possibilities that deserve further study," Dr. Patel said. "Sleeping less may affect changes in a person's basal metabolic rate (the number of calories you burn when you rest). Another contributor to weight regulation that has recently been discovered is called non-exercise associated thermogenesis, or NEAT, which refers to involuntary activity, such as fidgeting or standing instead of sitting. It may be that if you sleep less, you move around less, too, and therefore burn up fewer calories."
Both short and long sleeping times predict an increased risk of future body weight and fat gain in adults, according to a new study. The study, authored by Jean-Philippe Chaput, of Laval University in Quebec, Canada, focused on 276 adults between 21-64 years of age, whose body composition measurements and self-reported sleep duration were determined. Changes in fatty indices were compared between short (five to six hours), average (seven to eight hours) and long (nine to 10 hours) duration sleeper groups.
According to the results, after adjustment for age, sex, and baseline body mass index, short duration sleepers gained 1.98 kg more and long duration sleepers gained 1.58 kg more than did average duration sleepers over six years.
Short and long duration sleepers were 35 percent and 25 percent more likely to experience a 5 kg weight gain, respectively, as compared with average duration sleepers over six years. The risk of developing obesity was elevated for short and long duration sleepers as compared with average duration sleepers, with 27 percent and 21 percent increases in risk, respectively.
"Our study provides evidence that both short and long sleeping times predict an increased risk of future body weight and fat gain in adults. Furthermore, these results emphasize the need to add sleep duration to the list of environmental factors that are prevalent in our society and that contribute to weight gain and obesity. Since preventing obesity is important, a pragmatic approach adding sleep hygiene advice to encouragement towards a healthy diet and physical activity may help manage the obesity epidemic," said Chaput.
It is recommended that adults get between seven and eight hours of nightly sleep.
The American Academy of Sleep Medicine offers the following tips on how to get a good night's sleep:
- Follow a consistent bedtime routine.
- Establish a relaxing setting at bedtime.
- Get a full night's sleep every night.
- Avoid foods or drinks that contain caffeine, as well as any medicine that has a stimulant, prior to bedtime.
- Do not bring your worries to bed with you.
- Do not go to bed hungry, but don't eat a big meal before bedtime either.
- Avoid any rigorous exercise within six hours of your bedtime.
- Make your bedroom quiet, dark and a little bit cool.
- Get up at the same time every morning.
The study, authored by Martica H. Hall, PhD, associate professor of psychiatry at the University of Pittsburgh School of Medicine, and colleagues, focused on 1,214 adults between 30-54 years of age.
According to the results, the odds for having the metabolic syndrome increased by more than 45 percent in both short and long sleepers. Short sleep duration was common, with 20 percent of the sample reporting sleep durations of less than six hours per night. In contrast, only eight percent of the sample reported sleep durations of longer than eight hours per night.
"This relationship was strongest in the group of men and women who slept less than six hours per night. On average, the odds of having the metabolic syndrome were nearly doubled in men and women who slept less than six hours, compared to those who slept between seven and eight hours per night," said Dr. Hall.
Experts recommend that adults get between seven and eight hours of nightly sleep.
Too many hours
Don't hit the snooze alarm too many times: Too many hours in bed can cause as many sleep problems as too few, according to a new study.
"Long" sleepers who slumber more than eight hours a night and "short" sleepers who get fewer than seven hours of shuteye both report more sleep complaints than people who sleep in the "just right" zone of seven to eight hours, say Michael A. Grandner, B.A., and Daniel F. Kripke, M.D., of the University of California, San Diego. Their study appears in the journal Psychosomatic Medicine.
"Although it is unclear why long and short sleepers should have similar types of sleep complaints, these data challenge the assumption that more than seven or eight hours of sleep is associated with increased health and well-being," Grandner says.
Scientists know a lot more about problems associated with lack of sleep than they know about too much sleep, although some studies have shown a correlation between too much sleep and an increased risk of death in certain groups of people, according to Grandner and Kripke.
To find out if long sleepers have as many sleep complaints as the sleep-deprived, the researchers used data from nearly 100 adults interviewed in the National Sleep Foundation's 2001 Sleep in America Poll. The participants were asked how many hours they slept on a typical workday, not including naps, and whether they had any complaints about the quality of their sleep and sleep's effect on their daily activities.
Long sleepers reported more problems with falling asleep, waking up during the night, awaking too early, feeling "unrefreshed" upon waking up, and feeling sleepy during the day than those who slept seven or eight hours, the researchers found.
Sleep complaints were more common in both long and short sleepers than in those who got seven to eight hours of sleep a night. Women were more apt to be long sleepers than men were.
A new study is the first attempt to quantify the strength of the cross-sectional relationships between duration of sleep and obesity in both children and adults. Cross-sectional studies from around the world show a consistent increased risk of obesity among short sleepers in children and adults, the study found.
Francesco P. Cappuccio, MD, of Warwick Medical School in the United Kingdom, and colleagues performed a systematic search of publications on the relationship between short sleep duration and obesity risk. Criteria for inclusion were: report of duration of sleep as exposure, body mass index (BMI) as continuous outcome and prevalence of obesity as categorical outcome, number of participants, age and gender.
Of the 696 studies identified from the search, 12 studies on children and 17 studies on adults met the inclusion criteria.
For the children, 13 population samples from the 12 studies were included in the pool analysis, for a total of 30,002 participants from around the world. The subjects' age ranged from two to 20 years. Seven of 11 studies reported a significant association between short sleep duration and obesity.
For the adults, 22 population samples from the 17 studies were included in the pool analysis, for a total of 604,509 worldwide participants. The subjects' age ranged from 15-102 years. Seventeen population samples showed a significant association between short duration of sleep and obesity. Unlike studies in children, all studies in adults showed a consistent and significant negative association between hours of sleep and BMI.
According to Dr. Cappuccio, this study showed a consistent pattern of increased odds of being a short sleeper if you are obese, both in childhood and adulthood.
"By appraising the world literature, we were able to show some heterogeneity amongst studies in the world. However, there is a striking consistent overall association, in that both obese children and adults had a significantly increased risk of being short sleepers compared to normal weight individuals. The size of the association was comparable (1.89-fold increase in children and 1.55-fold increase in adults). This study is important as it confirms that this association is strong and might be of public health relevance. However, it also raises the unanswered question yet of whether this is a cause-effect association. Only prospective longitudinal studies will be able to address the outstanding question," said Dr. Cappuccio.
While an increasing number of adults are considered overweight, the number of overweight children is also on the rise. According to the National Heart, Lung and Blood Institute, the percentage of overweight children and teens has more than doubled in the past 30 years. Today, about 17 percent of American children aged two to 19 are overweight. An estimated 61 percent of U.S. adults aged 20-74 years are either overweight or obese. About 34 percent of these people are overweight and 27 percent or 50 million people are obese. While eating healthy and exercising regularly are important precautions to take to reduce one's chances of being overweight, getting enough sleep is equally as important.
Being overweight can lead to cardiovascular disease and type two diabetes, and can also increase the risk for developing obstructive sleep apnea (OSA), a sleep-related breathing disorder that causes your body to stop breathing during sleep. OSA, which can disturb your sleep numerous times on any given night, can result in daytime sleepiness, as well as elevate the risk for stroke, diabetes and heart disease. OSA is a serious sleep disorder that can be harmful, or even fatal, if left untreated. OSA occurs in about two percent of young children, four percent of men and two percent of women.
Snoring is a sound made in the upper airway of your throat as you sleep. It normally occurs as you breathe in air. It is a sign that your airway is being partially blocked. About one-half of people who snore loudly have OSA. OSA happens when the tissue in the back of the throat collapses to block the entire airway. This keeps air from getting in to the lungs. Almost everyone is likely to snore at one time or another. It has been found in all age groups. Estimates of snoring vary widely based on how it is defined. The rate of snoring in children is reported to be 10 to 12 percent, and in about 24 percent of adult women and 40 percent of adult men.
It is recommended that infants (three to 11 months) get 14 to 15 hours of nightly sleep, while toddlers get 12 to 14 hours, children in pre-school 11-13 hours and school-aged children between 10-11 hours. Adolescents are advised to get nine hours of nightly sleep and adults seven to eight hours.
The article, entitled, "Meta-analysis of Short Sleep Duration and Obesity in Children and Adults", was published in the May 1 issue of Sleep.
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