It is well known that is a risk factor for obstructive sleep apnoea (OSA). is an effective treatment for OSA, but the optimal timing of weight loss intervention is unknown. The aim of this study was to investigate whether a 12-month weight loss intervention delivered early (6 months after diagnosis of OSA) or late (12 months after diagnosis of OSA) was more effective in reducing OSA severity.

One hundred and fifty adults with OSA were randomly assigned to either an early or late intervention group. The intervention consisted of a 12-month programme of lifestyle modification, including dietary advice and physical activity. The primary outcome measure was the apnoea-hypopnoea index (AHI), a measure of OSA severity.

The results showed that the early intervention group had a significantly greater reduction in AHI than the late weight loss intervention group (-17.9 vs. -10.7, p=0.002). There was also a trend for greater reductions in body mass index (BMI) and waist circumference in the early weight loss intervention group compared to the late weight loss intervention group (-3.4 vs. -2.1 kg/m2, p=0.054 and -7.8 vs. -4.9 cm, p=0.051, respectively).

These findings suggest that a 12-month intervention delivered early (6 months after diagnosis of OSA) is more effective in reducing OSA severity than a weight loss intervention delivered late (12 months after diagnosis of OSA). This is likely due to the greater weight loss achieved in the early intervention group. These findings have important implications for the clinical management of OSA.