Fitness Club

A "good night's sleep" may be more important than we think. In addition to allowing us to feel rested, energetic and clear-thinking, studies have shown that there are connections between sleep and heart health. There also has been research demonstrating that sleep may affect body weight.

The latest to shed light on the sleep-weight connection is a study presented Sunday at the American Thoracic Society's 105th International Conference in San Diego, which indicates that body mass index, or BMI, is linked to length and quality of sleep in a surprisingly consistent fashion.

Researchers at Walter Reed Army Medical Center analyzed the sleep, activity and energy expenditures of 14 nurses who had volunteered for a heart-health program, part of the Integrative Cardiac Health Project.

The program included nutritional counseling, exercise training, stress management and sleep improvement.

The subjects were categorized either as "short sleepers" or "long sleepers." The short sleepers tended to have a higher BMI, averaging 28.3, compared with the long sleepers, whose average BMI was 24.5, according to lead investigator Arn Eliasson, MD.

The short sleepers also had greater difficulty falling asleep and staying asleep, he reported.

In spite of sleeping less, the overweight individuals in the study were more active than the normal weight participants by about 25 percent, and they burned almost 1,000 more calories per day, the study found.

Dr. Eliasson suggested that stress could disrupt the length and quality of sleep, as well as increase eating and other behaviors contributing to weight gain

Also, getting less sleep appears to cause a reduction in leptin, a hormone that triggers the feeling of fullness, perhaps causing short sleepers to eat more.

Leptin's Role

That raises the possibility of using leptin supplements to curb overeating.

"It is conceivable that leptin may become an agent that can be administered to help with weight management, but we are not there yet," Dr. Eliasson told Daily News Central. "Science is still sorting out the role that leptin plays in weight management and its variation with sleep."

He compared leptin to melatonin, in terms of the current level of scientific understanding of their roles.

"Melatonin pulses at predictable times that coincide with sleepy times of the day," noted Dr. Eliasson. "However, melatonin administration is not a reliable soporific agent. So what gives? Rozerem (ramelteon, a melatonin receptor agonist) has made it to market to help with sleep but it is less reliable for regulating sleep and inducing sleep than other agents like the new benzodiazepine receptor agonists. We know even less about leptin at this time."

Given the low likelihood that any magic pill will soon hit the market to make up for the effects of short sleep on body weight, one solution might be to get the proper amount of sleep. However, it can be tricky to figure out how much sleep you actually need for optimal functioning.

Calculating Sleep Needs

"Sleep needs vary greatly by individual, and there is no single good test to measure what an individual's sleep need is," Dr. Eliasson said.

On average, adults need regular episodes of about 8 hours 15 minutes per 24-hour period -- but that's a statistical average. The range is much broader: 4 hours to 10 hours, depending on the individual. Children require about 9 hours, and teens may need a little more. By adulthood, adults generally need about 8 hours per night, according to Dr. Eliasson.

Contrary to common belief, aging in itself doesn't reduce the amount of sleep required, he noted. Other things may conspire to interfere with a regular schedule of night-time sleeping though, such as medical conditions, orthopedic issues, medications, mental health and living circumstances -- whether one has to get up at the same time each morning to go to work or is retired, for example.

The result is that older people often break up their sleep into shorter episodes at night combined with daytime napping.

If you want to pinpoint the ideal amount of sleep for you, Dr. Eliasson suggests a six-month experiment: Attempt to get very regular amounts of a certain length of sleep for a few weeks, and keep a diary recording how you feel during that period. For example, get 7 hours of sleep per night for three to four weeks, noting what time you go to bed and get up, when you nap, and how you feel. Keep those regular sleep hours on week days, weekends and holidays. Then, expand your sleep time to 7 hours 20 minutes per night for three to four weeks recording similar variables. Then, expand to 7 hours 40 minutes per night for three to four weeks, and so on. Over six months, you will be able to zero in on the amount of sleep needed to feel rested and be functioning in peak form.

"This sort of experiment takes a lot of dedication and time, and not many people are willing or able to make this happen," Dr. Eliasson observed.

Primitive Biology

James Gangwisch, a post-doctoral fellow in psychiatric epidemiology at Columbia University, led an earlier study that found a relationship between sleep and obesity. He hypothesized that sleeping less might trigger our bodies to store more fat because we're still functioning biologically like primitive humans.

Early humans may have slept less during the long days of summer when food was plentiful, Gangwisch suggested, and their bodies may have then stored extra fat in anticipation of the winter, when food would be scarce. Perhaps the bodies of short sleepers now function as though it's perpetually summer, and they're always storing as much fat as possible.

"The theory involving storing fat in the summer during periods of short sleep appeals to common sense and is a tidy way to explain why short sleep may favor weight gain," Dr. Eliasson commented. "It would be lovely to have some measurable hormones or transmitters that would put names and faces on the characters of this unfolding story. Give science another five to 10 years!"

Future Research

Dr. Eliasson intends to continue researching this subject through the Integrative Cardiac Health Project at Walter Reed Army Medical Center.

There are currently plans in the works to evaluate the impact of stress reduction on sleep. Researchers will employ mechanisms such as exercise, meditation, acupuncture and acupressure to reduce stress and assess the effect on sleep induction, sleep duration, and energy expenditure. They hope to make their findings known in the next year or two.

Work in this field goes far beyond helping people achieve the pleasant aftermath of "a good night's sleep."

A body of research over the past decade has established that sleep has "a huge impact" on heart health, Dr. Eliasson pointed out.

"The association applies to both sleep quantity and sleep quality," he said. "Not getting enough sleep makes people vulnerable to heart attacks and stroke -- perhaps mediated through impact of insufficient sleep on glucose metabolism, cholesterol levels, and stress hormones. Likewise, poor quality sleep as demonstrated by the paradigm of sleep apnea increases risks for heart disease and stroke as well.

"The statistics are staggering," Dr. Eliasson continued, "in that more than mild sleep apnea -- moderate and severe sleep apnea -- is associated with a three- to four-fold increased chance for developing heart disease and a five- to six-fold increased chance for stroke.

"Our hard-charging, on-the-go, 24/7 lifestyle carries measurable risks," Dr. Eliasson concluded. Join the discussion! Send your comments to Daily News Central.

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