Patients recruited in the ESADA have been referred to a sleep center due to suspected obstructive sleep apnea (OSA). Enrolment is consecutive and the inclusion criteria enable essentially all new untreated patients independent of comorbidity, concomitant medication and degree of sleepiness.

A unique feature of the ESADA is a specifically designed web-based data collection format constructed for transfer of data to a central database located and coordinated at the Gothenburg University. A uniform clinical report format (CRF) module containing some 8 pages is used for registration of clinical data including anthropometrics, medical history, sleep data, clinical symptoms, limited clinical chemistry and medication. Recruited patients will generate a base cohort representing the various participating European Sleep Centres.

All patients referred to the participating laboratories are considered for inclusion into the cohort. Data from patients fulfilling all inclusion criteria are consecutively transferred to the centralized data base by use of a web based clinical report format (CRF) module.

A patient included into the data base is labelled only by a unique patient identification number. A detailed patient identification log is established at each study site. Blood samples for a future joint genetic analysis are kept under coded conditions at the discretion of each participating center. The CRF uses predefined modules in order to enable repeated entries into the data base for registration of consecutive follow up data, gathered according to local clinical routines. The ESADA also enables new and specific CRF modules for specific substudy (eg. specific patient groups, interventional trials, health economy evaluations) that may be initiated by initiatives between various centers within the network. These specific CRF modules are only accessible by those centres opting to participate in a specific substudy protocol

ESADA has appointed study monitors in order to provide education and instructions related to completion of the CRF modules. The monitors are responsible for continuous quality assurance of data entered into the data base and provide feed back to centres not complying with the minimal standard of study data entry. The initial term of the monitors is at least one year and has included at least one initiating site visit at each of the participating centres. Data are collectively owned by all participating and contributing centres. A joint study group consisting of 2 appointed representatives from each centre constitute the board of the foundation. Additional adjunct members from the different centres, without the right to vote at the board meeting, may be appointed by the board pending the specific research issues to be addressed. The ESADA network has received support from the COST action B26 and seeding grants from the CPAP industry for establishment of the organisation and the data base. The intention is to seek further economical support for the maintenece and expansion of the cohort from the European Framework Program (FP7). 

The first cross sectional analysis was planned at approximately 3,500 patients and a final recruitment goal is set at 7,000 patients with sleep disordered breathing. Beside the scientific opportunities offered, the ESADA will generate possibilities to achieve local and cross national sleep laboratory standardization within the EU, improvement of quality of care as well as increased scientific and clinical exchange of ideas and practices between different European sleep centers.