Insufficient Sleep Associated With Overweight And Obesity

Insufficient sleep causes neurocognitive changes such as excessive daytime sleepiness, altered mood, and increased risk for work-related injury and automotive accidents, according to background information in the article. It has been reported that the average American is currently getting less sleep than they did a century ago. With these declining sleep times there has also been an increase in the number of both obese and severely obese people in the U.S.

Robert D. Vorona, M.D., from Eastern Virginia Medical School, Norfolk, and colleagues examined patients' total sleep time per 24 hours in relation to their body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters). One thousand-one patients completed a questionnaire involving demographics, medical problems, sleep habits, and sleep disorders. The patients were classified as being of normal weight (BMI less than 25), overweight (BMI 25 – 29.9), obese (BMI 30 – 39.9), or severely obese (BMI 40 or greater). The average participant had a BMI of 30, and was 48 years old.

The researchers found that total sleep time decreased as BMI increased, except in the severely obese group. Men slept an average of 27 minutes less than women, and overweight and obese patients slept less than patients with normal BMIs. The difference in total sleep time between patients with a normal BMI and the other patients was 16 minutes per day, reaching 112 minutes, or 1.86 hours, over a week. In addition, night-shift work was associated with 42 minutes less total sleep time.

"Americans experience insufficient sleep and corpulent bodies. Clinicians are aware of the burden of obesity on patients," the authors write. "Our findings suggest that major extensions of sleep time may not be necessary, as an extra 20 minutes of sleep per night seems to be associated with a lower BMI. We caution that this study does not establish a cause-and-effect relationship between restricted sleep and obesity. Investigations demonstrating success in weight loss via extensions of sleep would help greatly to establish such a relationship."

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(Arch Intern Med. 2005; 165: 25 – 30. Available post-embargo at www.archinternmed.com)

Editor's Note: This study was supported by the Division of Sleep Medicine of the Department of Internal Medicine and the Department of Family Practice of Eastern Virginia Medical School and by the office of Dr. Feldman (co-author).

Weight, Fitness and Lifestyle Identified as Important Factors Contributing to Metabolic Syndrome

The metabolic syndrome, a group of several abnormalities, including obesity and high blood pressure, in one individual was identified in 10.4 percent of 36-year-old study participants, according to an article in the January 10 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.

According to background information in the article, the prevalence of metabolic syndrome, an important cause of cardiovascular disease, is increasing, especially in young individuals. Metabolic syndrome is identified when three or more of five risk factors are present: high blood pressure, high cholesterol, high triglyceride levels, high blood sugar levels, and a waist circumference of more than 94 cm [about 37 inches] in men and more than 80 cm [about 31.5 inches] in women. Although metabolic syndrome is believed to be caused principally by obesity, its determinants aren't completely understood.

Isabel Ferreira, Ph.D., from the Institute for Research in Extramural Medicine, VU University Medical Center, Amsterdam, the Netherlands, and colleagues analyzed to what extent specific variables determined the occurrence of the metabolic syndrome in patients from age 13 to 36 years. The researchers measured body fatness and fat distribution, cardiopulmonary fitness, and lifestyle factors in 364 participants from the Amsterdam Growth and Longitudinal Study, which began in 1977.

The prevalence of the metabolic syndrome at the age of 36 years was 10.4 percent. Participants with the metabolic syndrome, compared to those without, had a more significant increase in total body fatness and trunk fat beneath the skin; a decrease in cardiopulmonary fitness; an increase in physical activities of light-to-moderate intensity, but a decrease in more intense physical activities; a higher energy intake throughout the study; and a decreased likelihood of alcoholic beverage consumption. The metabolic syndrome was identified in 3.2 percent of the women and 18.3 percent of the men participating in the study.

"Fatness, fitness, and lifestyle are important determinants of the metabolic syndrome in young adults," the authors write. "More important, these associations were independent of each other and, therefore, represent separate potential targets for the prevention of metabolic syndrome. Our study further suggests that intervening early in life (e.g., in the period of transition from adolescence to adulthood) may be a fruitful area for prevention of the metabolic syndrome," they concluded.

(Arch Intern Med. 2005; 165: 42 – 45. Available post-embargo at www.archinternmed.com)

Editor's Note: Dr. Ferreira was supported by a joint research grant from the Foundation for Science and Technology (State Secretary of Science and Technology of Portugal) and the European Social Fund (Third European Community Framework Program).

Editorial: Sleepless in America

In an accompanying editorial, Joseph Bass, M.D., Ph.D., from Northwestern University Feinberg School of Medicine, and Fred W. Turek, M.D., Northwestern University, Evanston, Ill., commented on two obesity studies in this week's Archives of Internal Medicine.

"Obesity is a disease that, in just the past few decades, has been rising dramatically in developed countries and reached epidemic levels in the United States," the authors write. "Besides the social stigma attached to obesity, these trends are cause for concern because of the risks of secondary complications, including insulin resistance and type 2 diabetes mellitus, hyperlipidemia [high cholersterol], cardiovascular disease, hypertension [high blood pressure], stroke, cancer, and arthritis."

"In recent years, a new and unexpected 'obesity villain' has emerged, first from laboratory studies and now, as reported by Vorona et al in this issue of the ARCHIVES, in population-based studies: insufficient sleep....However, while there is a growing awareness among some sleep, metabolic, cardiovascular, and diabetes researchers that insufficient sleep could be leading to a cascade of disorders, few in the general medicine profession or in the lay public have yet made the connection."

"It is now critical to determine the importance of lack of sufficient sleep during the early formative years in putting our youth on a trajectory toward obesity and the metabolic syndrome--a trajectory that could be altered if sleep loss is indeed playing a role in this epidemic," the authors write.

(Arch Intern Med. 2005; 165: 15 – 16. Available post-embargo at www.archinternmed.com.)