[Comparison of obstructive sleep apnea in normal weighted and obese patients]

Obesity is a well established risk factor for developing an obstructive sleep apnea syndrome (OSAS). However, normal weighted patients can suffer from OSAS, too. This study compares breathing disorders and their effect on sleep of normal weighted and obese OSAS patients.

The main sleep parameters of 32 normal weighted OSAS patients (body mass index, BMI ≤ 25 kg/m2) were compared with those of 32 obese OSAS patients (BMI ≥ 35 kg/m2) with a virtually equal apnea-hypopnea index (AHI ± 3).

The mean AHI in both groups was 27.9/h (BMI ≤ 25 kg/m2) and 28.0/h (BMI ≥ 25 kg/m2), respectively. Sleep efficiency, relative percentages of sleep phases S1-S4 and REM, mean, minimal and maximal heart rate were not significantly different in statistic analysis in normal weighted and obese patients. Normal weighted OSAS patients had a higher apnea index (11.4 vs. 6.4, p=0.040), a higher minimal (81.3% vs. 71.7, p=0.003) and mean (94.9% vs. 92.8%, p=0.007) oxygen saturation, but a smaller hypopnea index (16.5 vs. 21.6, p=0.047) and a lower index of snoring (175.2 vs. 394.1, p<0.001) than their obese counterparts.

In OSAS patients with an equal AHI, the obese have fewer apneas, but more hypopneas, and a lower minimal oxygen saturation than normal weighted patients. The effect of OSAS on the sleep architecture, however, seems not to be associated with the patients' body weight.