Sleep Apnea Linked To Insulin Resistance, Independent Of Obesity

"In the past researchers have used body mass index, or BMI, as a proxy measure for body fat, but we know this to be a variable and crude tool to assess the true percentage of body fat," said Dr. Punjabi, lead investigator. "In addition, previous studies have used surrogate measurements to assess the body's response to insulin without investigating the interaction that occurs between reduced insulin sensitivity and increased insulin production in the body."

To address the shortcomings of previous studies, Dr. Punjabi and colleagues used two tools in their investigation into the link between SDB and insulin resistance: dual-energy x-ray absorptiometry (DEXA), a highly precise technique for assessing body fat, and frequently sampled intravenous glucose tolerance test (FSIVGTT), which provides a detailed picture of the subject's insulin sensitivity over time, rather than a simple snapshot at a specific moment.

They recruited 118 subjects, 39 who had no SDB, and 79 who were newly diagnosed with SDB but who had not been treated. Each subject underwent a sleep study to assess their level of SDB, and then underwent a FSIVGGT to determine their glucose metabolism and insulin sensitivity/production the following day.

"Our major finding was that, as we suspected, SDB was strongly associated with a decrease in the three major metabolic pathways that the body uses to metabolize glucose - insulin sensitivity, glucose effectiveness, and pancreatic cell function - independent of adiposity," said Dr. Punjabi. "What our research tells us is that SDB is characterized by multiple physiological deficits that increase the predisposition for type 2 diabetes mellitus."
American Journal of Respiratory and Critical Care Medicine, Feb. 2009