The effect of a very low-calorie diet-induced weight loss on the severity of obstructive sleep apnoea and autonomic nervous function in obese patients with obstructive sleep apnoea syndrome

The aim of this study was to examine the effect of a very low-calorie diet (VLCD)-induced weight loss on the severity of obstructive sleep apnoea (OSA), blood pressure and cardiac autonomic regulation in obese patients with obstructive sleep apnoea syndrome (OSAS). A total of 15 overweight patients (14 men and one woman, body weight 114 +/- 20 kg, age 52 +/- 9 years, range 39-67 years) with OSAS were studied prospectively. They were advised to follow a 2.51-3.35 MJ (600-800 kcal) diet daily for a 3-month period. In the beginning of the study, the patients underwent nocturnal sleep studies, autonomic function tests and 24-h electrocardiograph (ECG) recording. In addition, 15 age-matched, normal-weight subjects were studied. They underwent the Valsalva test, the deep-breathing test and assessment of heart rate variability at rest. The sleep studies and autonomic function tests were repeated after the weight loss period. There was a significant reduction in weight (114 +/- 20 kg to 105 +/- 21 kg, P<0.001), the weight loss being 9.2 +/- 4.0 kg (range 2.3-19.5 kg). This was associated with a significant improvement in the oxygen desaturation index (ODI4) during sleep (31 +/- 20-19 +/- 18, P<0.001). Before the weight loss the OSAS patients had significantly higher blood pressure (150 +/- 18 vs. 134 +/- 20, P<0.05, for systolic blood pressure, 98 +/- 10 vs. 85 +/- 13, P<0.05, for diastolic blood pressure) and heart rate (67 +/- 10 beats min(-1) vs. 60 +/- 13, P<0.05) at rest than the control group. They had also lower baroreflex sensitivity (4.7 +/- 2.8 ms mmHg(-1) vs. 10.8 +/- 7.1 ms mmHg(-1), P<0.01). During the weight reduction, the blood pressure declined significantly, and the baroreflex sensitivity increased by 49%. In conclusion, our experience shows that weight loss with VLCD is an effective treatment for OSAS. Weight loss improved significantly sleep apnoea and had favourable effects on blood pressure and baroreflex sensitivity that may have prognostic implications.