Nocturnal hypoxia and sleep apnoea in asymptomatic obese men

A disorder of breathing during sleep with a fall in arterial oxygen saturation (%SaO2) and apnoea is reported in association with obesity. In obese women an increased severity of oxygen desaturation and the appearance of sleep apnoea is often seen after the menopause whereas the factors influencing sleep-breathing patterns in obese men are uncertain. We investigated this by studying respiration during sleep in 20 asymptomatic obese men (mean wt 125 kg, age range 18-59 y) and 20 control men of normal weight (mean wt 67 kg, age range 19-67 y). In the obese men the mean awake %SaO2 measured in the supine position was significantly less than controls (obese 95 +/- 0.4, controls 97 +/- 0.2, P less than 0.01) and a greater fall in %SaO2 occurred in this group during sleep (mean asleep %SaO2 obese 90.5 +/- 0.9, controls 96 +/- 0.2, P less than 0.01). In addition, the minimum asleep %SaO2 was significantly less in the obese (mean minimum %SaO2 obese 75 +/- 3, controls 93 +/- 0.9, P less than 0.001). Sleep apnoea was uncommon and infrequent in the controls but was seen in nine obese men and was frequent throughout the night in seven of them. In the obese group increasing age and increasing obesity were not significantly correlated with an increased severity of nocturnal oxygen desaturation. We conclude that disordered sleep-breathing with marked oxygen desaturation and apnoea is a common finding in extremely obese men of all ages and suggest that this results from the mechanical impedence of breathing due to abdominal adipose tissue combined with abnormal central respiratory control.