Effect of Obstructive Sleep Apnea on Glucose Control and Cognitive Function

Inclusion Criteria: * BMI ≥ 25kg/m2 * impaired glucose tolerance which defined as plasma glucose at the range of 7.8 and 11 mmol/l 2 hours after 75g oral glucose solution intake, * willing to participate in lifestyle modification program * and capable of using continuous glucose monitoring (CGM) as judged by investigator Exclusion Criteria: 1. Lactating or pregnant, 2. known diabetes, current or previous use of glucose lowering drug 3. current participation in other weight loss or lifestyle interventions, or use of weight loss drugs, 4. current use of steroids 5. uncontrolled thyrotoxicosis 6. allergy to medical grade adhesives 7. known obstructive sleep apnea on continuous positive airway pressure therapy 8. symptoms of cognitive deterioration (according to the Hong Kong Montreal Cognitive Assessment (HK-MoCA) at the score of \<21) 9. predominant central sleep apnea 10. uncontrolled hypertension (blood pressure \>140/90mmHg) or requiring more than two anti-hypertensive medication 11. history of stroke or brain injury, 12. unstable cardiovascular disease (e.g. recent unstable angina or myocardial infarction within the previous 6 months or severe left ventricular failure; neuromuscular disease affecting or potentially affecting respiratory muscles; moderate to severe respiratory disease (i.e. breathlessness affecting activities of daily living) or documented hypoxemia or awake SaO2 \<92%) 13. psychiatric disease that limits the ability to give informed consent or complete the study 14. Use of psychoactive medication.