Studies Link Health Issues to Sleep Apnea
Reported January 28, 2009
(Ivanhoe Newswire) — Using newer, more accurate measuring tools, researchers have discovered a link between sleep apnea and pre-diabetic changes in insulin production and glucose metabolism.
In previous studies, researchers used body mass index to measure body fat, but scientists now believe that method is prone to errors. For this study, Naresh Punjabi, M.D., Ph.D., and colleagues used 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 person’s insulin sensitivity over time rather than a simple snapshot at a specific moment.
Scientists recruited 118 patients, including 39 who had no sleep disordered breathing (SDB) and 79 who were newly diagnosed with SDB but who had not been treated. Each person underwent a sleep study to assess their level of SDB, 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 [obesity],” Punjabi said.
He said this research shows that SDB is characterized by multiple physiological deficits that increase the predisposition for type 2 diabetes.
In a separate study, researchers at Johns Hopkins Bayview Medical Center Bariatric Surgery Clinic found that the chronic intermittent hypoxia — a lack of adequate oxygen supply — that often characterizes obstructive sleep apnea (OSA) is also independently linked to the progression of liver disease.
Researchers recruited 90 severely obese patients who were preparing to undergo gastric bypass surgery but did not have known diagnoses of OSA, a common form of SDB. Each person underwent a sleep study and blood tests for markers of liver function, insulin resistance and systemic inflammation.
A link was found between OSA and insulin resistance and further linked it to the level of hypoxemia experienced during the night versus simply the number of apneic events.
Researchers said their findings were clear: obesity and obstructive sleep apnea exert separate and perhaps additive negative effects on insulin resistance and the liver.
In a separate study, Canadian researchers found yet another risk factor common to obesity and OSA: prolonged daytime sitting or standing. In fact, even when a sedentary lifestyle does not lead to obesity, it may still lead to OSA and its health risks.
This is caused by a daytime fluid build-up in the calves, caused by prolonged inactivity, shifting to the upper body at night when a person lies in bed.
“It is therefore plausible that some of the displaced fluid might reach the neck and predispose to upper airway constriction,” researchers said.
SOURCE: American Journal of Respiratory and Critical Care Medicine, February 2009