The sixth survey of the Tromso Study (Tromso 6) in 2007-08: Collaborative research in the interface between clinical medicine and epidemiology: Study objectives, design, data collection procedures, and attendance in a multipurpose population-based health survey

Aims: To provide a synopsis of the sixth survey of the Tromso Study, Tromso 6, objectives and new target areas, study design, follow-up studies, data collection, attendance, and participant characteristics. Methods: The Tromso Study, initiated in 1974, is an epidemiological, prospective study of health conditions and chronic diseases, and a resource for the surveillance of disease risk factors. The purpose of Tromso 6 (2007-08) was to collect novel and repeated measurements of exposure data and to assess levels of disease risk factors. Tromso 6 included a main study that comprised two screening visits and several follow-up studies. Main study data collection: First visit (n=12,984): questionnaires, interviews, measurements of height, weight, hip and waist circumference, heart rate, blood pressure, forearm bone density, grip strength, pain sensitivity measurements, and blood and hair samples and nose and throat swab cultures. Second visit (n=7307): sampling of biological specimens (blood, urine, nose and throat swab cultures) and clinical examinations (12-lead electrocardiography, cognitive tests, visual acuity test, retinal photography, carotid ultrasound, spirometry, dual-energy X-ray absorptiometry, and echocardiography. Results: A total of 12,984 participants aged 30-87 years were examined. The attendance rate was 66%, lower than in previous Tromso Study surveys. The attendance was lowest in the youngest and oldest, those invited for the first time, and lower in men than women. Conclusions: The completion of the survey with this comprehensive data collection went satisfactorily. The decreasing attendance rate calls for new recruitment strategies and optimisation of the study organisation to facilitate attendance.