METABOLIC IMPACTS OF SLEEP APNEA
Obstructive sleep apnea (OSA) is associated with diabetes and cardiovascular disease, but mechanisms are unclear. By comparing blood samples of OSA patients asleep with or without CPAP, we discovered that OSA increases plasma free fatty acids (FFA) and glucose during sleep. Now, we are examining the underlying mechanisms and consequences of these metabolic changes, using stable isotopes to measure the flux of fat and glucose in the bloodstream.
SLEEP AT HIGH ALTITUDE
Little is known about effects of high altitude on chronic sleep health. We are studying effects of high altitude on sleep, breathing, and metabolism in inhabitants of Puno, Peru (3825 m, or 2.5 miles above sea level). In adults at high altitude we showed that hypoxia was associated with risks of metabolic syndrome and inflammation. We also found that highlanders (Puno) have a higher prevalence of sleep apnea than lowlanders (Lima, sea level) and that decreased oxygen levels while awake predicted the presence of sleep apnea at high altitude. Our current work focuses on developing inexpensive and readily deployable treatments for sleep apnea and low oxygen levels in highlanders.
TARGETED HYPOGLOSSAL STIMULATION FOR SLEEP APNEA
Many patients cannot tolerate continuous positive airway pressure (CPAP) for OSA and alternative therapies are lacking. OSA may be treated by stimulating the hypoglossal nerve, which controls the tone of the tongue muscle during sleep. Already, one such device has been tested in clinical trials. However, existing technology only stimulates the genioglossus muscle in a non-targeted manner which may limit its effectiveness. Our laboratory is examining the effects of selective stimulation of various lingual muscles, singly or in combination, on upper airway function.
EFFECTS OF DELAYED DINNER ON METABOLISM AND SLEEP
Consuming calories later in the day is associated with obesity and metabolic syndrome. We hypothesize that eating a late dinner alters metabolic function during sleep in a manner that promotes obesity. We are comparing the metabolic effects of routine dinnertime (18:00) versus late dinnertime (22:00) with a fixed sleep period (23:00-07:00) on the metabolic profile of healthy volunteers in a randomized crossover study. This study involves novel use of stable isotopes to trace fatty acid oxidation.