Study highlights:
• People who slept less than six hours a night during the work week were nearly five times more likely to develop abnormal fasting blood sugar levels over a six-year period.
• Impaired fasting blood glucose observed in these “short sleepers” is a possible precursor to type 2 diabetes.
• Researchers do not believe there is a genetic basis for their findings and hope their study leads to more research on sleep duration and its relationship to disease. 

PALM HARBOR, Fla., March 11, 2009 — People who sleep less than six hours a night appear to have a higher risk of developing impaired fasting glucose — a condition that can precede type 2 diabetes, researchers reported at the American Heart Association’s 49th Annual Conference on Cardiovascular Disease Epidemiology and Prevention.

Type 2 diabetes, the most common form of diabetes, appears most often in middle-aged adults. Adolescents and young adults, however, are developing type 2 diabetes at an alarming rate. It develops when the body makes relatively too much insulin and doesn’t efficiently use the insulin it makes (insulin resistance).

Participants who slept on average less than six hours a night during the work week, when followed over six years, were 4.56 times more likely than those getting six to eight hours of sleep to convert from normal blood sugar levels to impaired fasting glucose, researchers said.

“This study supports growing evidence of the association of inadequate sleep with adverse health issues. Sleep should be assessed in the clinical setting as part of well-care visits throughout the life cycle,” said Lisa Rafalson, Ph.D., lead author of the study and National Research Service Award fellow and research assistant professor at the University at Buffalo in New York.

“While previous studies have suggested that there may be many genes that each have a very small effect on the risk of diabetes, there is no known genetic predisposition to sleep disturbances that could explain our study’s results, especially in this limited sample size,” Rafalson said. “It is more likely that pathways involving hormones and the nervous system are involved in the impaired-sleep/fasting glucose association.”

Researchers conducted a matched, nested case-control study to address whether sleep duration at baseline predicted progression from normal to impaired fasting glucose during six years of follow-up in the Western New York Health Study. From 1,455 participants, the team identified 91 whose fasting blood glucose levels of less than 100 milligrams per deciliter (mg/dL) during baseline exams in 1996–2001 had risen to between 100 mg/dL and 125 mg/dL at follow-up exams in 2003–2004.

The 91 were matched three-to-one with 273 controls whose glucose levels were below 100 mg/dL at baseline and follow-up. Researchers also matched the groups according to gender, race/ethnicity and year of study enrollment.

Sleep duration was self-reported using the Stanford seven-day physical activity recall questionnaire, with patients categorized by their daily work week (Sunday through Thursday) sleep duration: short-sleepers (less than six hours, 25 participants), long-sleepers (more than eight hours, 24 participants) and mid-sleepers (six-to-eight-hour sleepers, 314 participants). Sleep data was unavailable on one person.

After adjusting for age, body mass index, glucose and insulin concentrations, heart rate, high blood pressure, family history of diabetes and symptoms of depression, the researchers found a significantly increased risk of developing impaired fasting glucose among short-sleepers compared to the mid-sleepers. Compared to the mid-sleepers, long-sleepers showed no association with impaired fasting glucose, the researchers report.

“Our findings will hopefully spur additional research into this very complex area of sleep and illness,” Rafalson said.

Co-authors are: Richard P. Donahue, Ph.D., M.P.H.; Michael LaMonte, Ph.D., M.P.H.; Joan Dorn, Ph.D.; Maurizio Trevisan, M.D., M.S.; Saverio Stranges, M.D., Ph.D.; and Jacek Dmochowski, Ph.D. Individual author disclosures are available on the abstract.

The study was funded by the National Institutes of Health.

NR09 – 1036 (Epi09/Rafalson)

(Note: Actual presentation time is 6 p.m. ET, Wednesday, March 11, 2009)

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Abstract P119 – Researchers find link between sleep loss, high blood pressure in women
Researchers report a link between sleep duration and increased risk of high blood pressure — but only in women.

The study included 3,027 cardiovascular disease-free, middle-aged white men (43.5 percent) and women (56.5 percent). High blood pressure was defined as systolic pressure of 140 millimeters of mercury (mm Hg) and above, or diastolic pressure 90 mm Hg and above, or use of anti-hypertensive drugs.

The researchers compared short duration (less than 6 hours) to mid-level (6–8 hours) of sleep and calculated participants’ odds of developing high blood pressure, while accounting for many potential disease predictors including marital status, income, education, physical activity, smoking and others.

Researchers found:
• Short duration of sleep was associated with a significant increased risk of high blood pressure in women compared to sleeping 6–8 hours per day.
• No significant association was seen in men.
• Sleep’s effect was stronger in pre-menopausal women than post-menopausal women.

By increasing the risk of high blood pressure, sleep loss may lead to cardiovascular disease in women, researchers said. But prospective and laboratory evidence is necessary to support the association.

(Note: Actual presentation time is 6 p.m. ET, Wednesday, March 11, 2009)

Abstract P343 – Poor sleep quality may put children at risk for obesity
In a study of 967 students (430 girls, 537 boys) 9 to 14 years old, researchers gathered data on sleep behaviors and measured height and weight to calculate body mass index (BMI). Using parental questionnaires, sleep difficulties were classified as “often” or “sometimes” based on whether a child had one or more sleep problems. Standard age- and sex-specific height and weight measures determined BMI status. Overweight is defined as a BMI of 25 to less than 30 and obesity is defined as a BMI of 30 or greater.

Researchers found that among the participants:
• Childhood overweight was 22 percent.
• Childhood obesity was 10.3 percent.
• Sleep problems “often” occurred in 36 percent.
• Compared to those “never” or “sometimes” having sleeping problems, children having problems “often” had 62 percent higher odds of being obese.

Potential confounding variables included child gender, age, mother’s marital status, ethnicity and family income. No interactions were found between sleeping problems and current smoke exposure.
“Poor sleeping quality is associated with childhood obesity, but further study should focus on the direction of the association,” researchers said.
 
(Note: Actual presentation time is 5 p.m. ET, Friday, March 13, 2009.)

Abstract P370 – Stress plus poor sleep quality may increase obesity in African Americans
Psychosocial stress appears to strengthen an inverse correlation between sleep quality and obesity in African Americans, new research suggests.

In a study of 1,515 African-American residents of Atlanta, ages 30 to 65, researchers measured body mass index and computed global sleep quality scores (healthy sleep, poor sleep, chronic sleep disorder). Individual Pittsburgh Sleep Quality Index (PSQI) scores also were evaluated.

General perceived stress was derived according to a standard scale and divided into thirds to test interactions. “Covariates” included age, gender, physical activity, smoking, socioeconomic status and cardiovascular disease.

“After multivariate adjustment, sleep quality as assessed by global sleep quality score showed no association with obesity (odds ratio 1.02),” the researchers said. Nevertheless, general perceived stress “positively interacted with global sleep quality to significantly increase the likelihood of obesity in people with poor sleep quality.” Stress also interacted with two PSQI domains — “daytime dysfunction” and “sleep latency” — to increase the likelihood of obesity.

“We found that poor sleep quality increases the likelihood of obesity, and this association is positively modulated by perceived stress,” researchers said. “Previous results and ours may suggest an issue of sensitivity of the PSQI scale or of severity of sleep disease.”

(Note: Actual presentation time is 5 p.m. ET, Friday, March 13, 2009.)

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