WASHINGTON: A recent study has revealed that short sleep times in patients with chronic medical diagnoses increases the risk of obesity.

The researchers surveyed 200 patients attending internal medicine clinics about their sleep habits, lifestyle characteristics, and medical diagnoses.

The findings revealed people with a sleep time of less than seven hours had a notably increased possibility of obesity defined by a body mass index compared to the reference group of eight to nine hours.

The researchers believe that there is a U-shaped relationship between obesity and sleep time in women suggesting that woman who had both short and long sleep times were more likely to be obese.

The patients included young age (18 to 49 years), not smoking, drinking alcohol, hypertension, diabetes, and sleep apnea.

Kenneth Nugent, MD, of Texas Tech University and lead author of the study said short sleep times have an association with obesity in adults with chronic medical problems.

"Our study demonstrates that short sleep times have an association with obesity in adults with chronic medical problems and that chronic disease and attendant therapies and/or changes in physical activities do not obscure this relationship," said Nugent.

"This study suggests that adults should sleep eight to nine hours per night to maintain optimal weight, he added.

The weight and obstructive sleep apnea (OSA), makes the neck thicker thereby increasing the level of fat in the back of the throat and narrowing the airway.

With more fat in the throat the airway is more likely to be blocked.

People with OSA are obese and have a neck size of more than 17 inches. Many people with OSA also have high blood pressure.

It is believed that four percent of men and two percent of women have OSA.

The study is published in the December 15 issue of the Journal of Clinical Sleep Medicine (JCSM).