Lifestyle Modification Program to Treat Obstructive Sleep Apnea Patients

Obstructive sleep apnea syndrome (OSAS) is a common form of sleep-disordered breathing (SDB) characterized by repetitive episodes of cessation of breathing during sleep due to upper airway collapse. It causes sleep fragmentation, disabling daytime sleepiness, impaired cognitive function and poor quality of life. In addition, OSAS is associated with non-fatal and fatal cardiovascular consequences including sudden death, in addition to an increased risk of road traffic accidents.

OSAS is equally common among the middle-aged male Caucasian and Hong Kong (HK) Chinese populations with prevalence rates of at least 4%. The prevalence and severity of OSAS tend to increase through adult life, peaking in the late fifties to mid sixties, after which it fails to increase or decrease. Another group of investigators reported high prevalence rates of SDB in a group aged 65-95 years of 70% for men and 56% for women, at least double those reported for middle-aged cohorts.

Risk factors for OSA include obesity, increasing age, being male, abnormal craniofacial morphology, nasal obstruction, genetic factors. OSA is associated with several cardiovascular consequences and social consequences e.g. motor vehicle accidents, impaired cognitive performance, depression. Various epidemiologic studies have shown an association between OSA and hypertension. In cross-sectional study, OSA was associated with increased prevalence of self-reported heart failure and stroke. OSA has been shown to be independently associated with coronary artery disease after adjustment for traditionally considered risk factors.

Continuous positive airway pressure (CPAP) is considered as the first-line treatment for OSA. Oral appliance has been shown to reduce the severity of sleep disordered breathing and leads to symptomatic improvement especially in mild to moderate OSA. The compliance with CPAP is low particularly in mild or moderate OSA patients and it is not a curative treatment of OSA. It has to be used in every night on a regular basis. Weight reduction has always been advocated in patients with OSA who are overweight and may lead to improvement in the severity of OSA. A population-based longitudinal study showed that a 10% weight loss predicted a 26% decrease in apnoea-hypopnoea index (AHI), a count of the number of upper airway obstructions per hour of sleep.

The existing studies about weight loss are limited by small sample size, short duration (<6 months), focus on very low calorie diet program or surgically induced weight loss program only. However, none of them have applied lifestyle modification program (LMP) which emphasizes on long term lifestyle and behavior change. Therefore, the investigators plan to conduct a randomized controlled trial among Chinese OSA patients by comparing the efficacy of LMP against usual clinical lifestyle advice alone on the improvement of OSA symptoms.

Aim of the study:

The investigators aim to test the hypothesis that LMP is superior to lifestyle advice alone in the management of Chinese patients with OSA. The primary outcome measure is the change of AHI. The secondary outcome measures are changes in quality of life, symptoms related to OSA, glucose, and insulin metabolism parameters.

Hypothesis:

The investigators hypothesize that more OSA patients in a low glycemic index dietary intervention program than patients receiving simple lifestyle advice alone will have reduction in AHI.