The Tromsø study 1974-2016: 40 years of cardiovascular research.

The rapid increase of coronary heart disease mortality in Northern Norway during 1951-1970 was why the newly established University of Tromsø decided to start a study to identify major operating cardiovascular risk factors. The first Tromsø survey in 1974 suggested that the relatively high cardiovascular mortality was associated with elevated cholesterol levels and high prevalence of smoking, while high-density-lipoprotein-cholesterol (HDL-C) was identified as a preventive factor. After 1974, six more surveys including both genders (aged 20-89 years) were undertaken. The second survey (1979) revealed the cholesterol increasing effect of coffee. Echocardiographic examinations, ECG, and ultrasound of carotid arteries were introduced in later surveys, and intervention studies were established. Repeated carotid measurements showed that inflammation was involved in novel plaque formation, while HDL-C was protective. Moderate physical activity protected against atrial fibrillation but hard exercise increased the risk. Obesity, hypertension and smoking increased the risk of aortic stenosis, and diastolic dysfunction predicted development of atrial fibrillation. Dilated left atria predicted stroke, especially for individuals without known atrial fibrillation. Total cholesterol, blood pressure and smoking declined after 1974, corresponding to the subsequent decline in coronary heart disease mortality. Reduced incidence accounted for 40% of the mortality decline, while a substantial reduction in case fatality explained the remaining 60%.