Introduction:
Type 2 diabetes (T2DM) and obstructive sleep apnoea (OSA) are improved by weight-loss and may enter remission.1-7 The use of a very-low energy diet (VLED) rapidly improves glycaemic control, and can achieve remission in patients with short and long duration of diabetes.1,2 However, it has been suggested that obese patients with OSA may be refractory to the acute beneficial metabolic effects of a VLED.8
Method:
Obese participants with T2DM and either treated OSA on continuous positive airway pressure therapy (CPAP n=8) or without known OSA (non-CPAP n=8) underwent 12-weeks of VLED (450-880kcal/day). Metabolic parameters were assessed at baseline and 12-weeks. Sleep studies were performed in participants with positive screening scores, or known OSA.
Results:
Baseline characteristics of the two groups demonstrated equivalent glycaemic control (HbA1c 7.4%), but a higher BMI (53.9±3.1kg/m2 vs. 44.8±1.0kg/m2; p=0.008), body-weight (149.7±8.2kg vs. 120.3±120.3kg; p=0.002) and waist circumference (148.6±2.6cm vs. 131.0±4.1cm; p=0.001) in the group treated with CPAP. Undiagnosed moderate-severe OSA (Apneoa Hypopnoea index: AHI≥15) was identified in 3/8 untreated participants. Similar improvement was observed in both CPAP and non-CPAP groups for weight-loss (-17.4±2.5kg vs. -15.4±2.6kg; p=0.3), waist circumference (-12.6±1.9cm vs. -13.3±2.0cm; p=0.4) and HbA1c (-1.5±0.4% vs. -1.4±0.5%; p=0.4) despite reduction in insulin doses (-35%). The AHI remained unchanged in the participants on CPAP (22.1 to 25.3 events/hour measured without CPAP; p=0.31) and the non-CPAP group (31.5 to 26.1 events/hour; p=0.53). The VLED was equally effective in patients with mild OSA (AHI<15; n=6) compared to moderate-severe OSA (n=7) in reducing body-weight (-18.5±2.6kg vs -17±2.2kg; p=0.3); waist circumference (-13.3±2.1cm vs -12.4±2.3cm; p=0.4) and HbA1c (-1.4±0.5% vs -1.6±0.4%; p=0.4).
Conclusion:
Weight-loss using a VLED is an effective means of improving glycaemic control and reducing insulin requirements in patients with T2DM. This metabolic benefit is seen in obese patients irrespective of severity of OSA or treatment with CPAP.