The WA Sleep Health Study

Obstructive sleep apnoea (OSA) is a common disorder in Australia associated with substantial social and economic costs globally due to its high prevalence in the community, marked effects on cognitive and general function, and the increased risk of adverse health complications (including hypertension, myocardial infarction and stroke). OSA is characterized by sleep-induced partial and/or complete obstruction of the pharyngeal airway resulting in repetitive arousal from sleep, hypoxia and hypercapnoea. The presence and severity of OSA is most commonly diagnosed using physiological data obtained from overnight polysomnography (PSG). OSA most likely results from multiple interacting genetic and environmental factors. Despite the rising incidence and serious complications of OSA, its natural history and aetiology remain poorly defined. In part, this is because there have been few large, population-based epidemiological or genetic studies internationally. Currently no clinic-based, whole population longitudinal cohorts exist for OSA. The lack of large, population-based samples with which to undertake epidemiological and genetic research is currently a critical limiting factor for aetiological studies of OSA.

Aim

The primary aim of this project is to establish a population-based database resource and linked biospecimen resource (DNA plus sera) in order to investigate the clinical and genetic epidemiology of OSA.

Specific Aims

1. To collate and enter all of the extant sleep-associated data obtained in Western Australia since 1988 (including historical paper records) into a core database - The WA Sleep Health Study (WASHS) database.
2. To establish a WASHS biospecimen bank of DNA and sera from all consenting OSA patients in WA.
3. To investigate the aetiology, natural history and prognosis of patients with OSA in WA using the WASHS database.
4. To investigate the inter-relationship of OSA to other diseases, including cardiovascular disease, cerebrovascular disease, diabetes and obesity using the WASHS database and the core WA Data Linkage System.
5. To investigate the familial aggregation of OSA and associated conditions using the core WA Data Linkage System, specifically the Family Connections resource.

Methods

Data from all sleep studies performed in WA since 1988 (~34,000 studies) will be entered to create the WASHS database. A total of ~29,000 historical sleep studies will need to be transferred from paper to electronic media. We also plan to collect a total of 10,000 DNA and serum samples for the WASHS Biospecimen Bank. Past clinic patients (n=5,000) will be approached by mail to request donation of a specimen. An additional 5,000 consenting patients will have blood drawn during the course of this study (2006-2008). The stored DNA from consenting patients will enable future molecular genetic studies (funding to be sought separately).

Significance

The WASHS resource will be an important tool to increase our understanding of the aetiology, mechanisms and prognosis of OSA and may therefore lead to improved treatment and preventive strategies for OSA. The WASHS resource will represent the only population-based PSG dataset with complete ascertainment in the world, and will also comprise the largest single DNA resource for the molecular genetic investigation of OSA in the world. A unique and important advantage of creating this database in WA is the potential to link the WASHS database to the core WA Data Linkage System which includes population-based health data on all deaths, hospitalisations, and medication use. Therefore, it will be possible to investigate the changing roles of environment and genes in OSA and related disorders over the entire life span. WASHS will enable the investigation of the effect of OSA therapy (e.g., CPAP) on morbidity and mortality, and an accurate estimate of the incidence and prevalence of physician-diagnosed OSA. WASHS will also foster international and national collaboration between researchers from a number of disciplines (eg sleep physicians, cardiologists, endocrinologists, epidemiologists, psychiatrists, neurologists, and physiologists).