SDB in Mildly Obese Men Associated with Glucose Intolerance and Insulin Resistance

March 30, 2002

Researchers studying a community sample of 135 healthy but mildly obese men found that moderate to severe sleep-disordered breathing (SDB), as measured by a sleep test, was associated with glucose intolerance and insulin resistance.

In the first issue for March of the American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine, Naresh M. Punjabi, M.D., Ph.D., of the Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, along with six associates, reported that SDB was relatively common in the study group (originally 150 men) with a 40 to 60 percent prevalence for abnormal breathing events during sleep. However, when investigators used a more stringent SDB definition involving associated objective daytime sleepiness, this criterion lowered the range to 20 to 30 percent of the individuals in the sample.

The authors said that the SDB was associated with impaired glucose tolerance and insulin resistance independent of obesity. They categorized their population as "relatively healthy" since the selection process excluded those with existing diabetes and cardiovascular disease.

In insulin resistance, the body produces antibodies to insulin which interfere with its activity. In glucose intolerance, a glucose tolerance test assesses the ability of the body to metabolize its principal blood sugar.

Although the researchers did not find a relationship between fasting glucose and insulin levels and the severity of SDB, they saw a significant association between the apnea-hypopnea index and 2-hour glucose and insulin
levels.

SDB is recognized as a chronic condition characterized by recurring episodes of partial or complete cessation of airflow during sleep. These respiratory disturbances often are accompanied by a fall in the amount of oxygen in the blood (hypoxia) and brief arousal from sleep.

In this study, apnea was defined as a complete cessation of airflow for at least 10 seconds. Hypopnea was defined either as a reduction in airflow of at least 10 seconds duration associated with electronencephalogic arousal or a 4 percent drop in oxygen saturation in the blood.

Among the study group, polysomnography revealed an average apnea-hypopnea index (AHI) of 17.4 events per hour.

According to the authors, an AHI of over 5 events per hour was associated with worsening glucose tolerance, after adjusting for body mass index and percent of bodily fat.

The results of the oral glucose tolerance test showed that 63 subjects (46.7 percent) had a normal response, 54 individuals (40 percent) had an impaired response, and 18 persons (13.3 percent) showed a diabetic reading.

"Our data demonstrate a dose-response relationship between the severity of sleep-disordered breathing and degree of metabolic dysfunction," said Dr. Punjabi. "Thus, these data suggest that early metabolic dysfunction occurs with sleep-disordered breathing before overt clinical manifestations of underlying disease."

They noted that impaired glucose tolerance and worsening insulin resistance can lead to further weight gain, exacerbating the severity of disordered breathing during sleep.

They urge that early identification of SDB be considered in the mildly obese, particularly those who complain of sleep-related symptoms.

Contact

Naresh M. Punjabi, M.D., Ph.D., Division of Pulmonary and Critical
Care Medicine, Johns Hopkins Asthma and Allergy Center, 5501 Hopkins Bayview Circle
Baltimore, Maryland 21224
Telephone: (410) 550-5405
Fax: (410) 550-2612
E-mail: naresh@jhmi.edu