The aim is to investigate whether screening with long-term ECG monitoring in individuals with elevated NT-proBNP leads to a lower incidence of ischeamic stroke and death from vascular causes. The project is a sub-study within the 8th wave of the population based Tromsø Study. Information on previous diseases, medication use, and risk factors is collected through questionnaires, blood samples, and measurements of height, weight, blood pressure, and ECG. A total of 4,000 individuals with NT-proBNP levels above the median, without previously known atrial fibrillation (AF) or ongoing anticoagulation therapy, will be randomized to either long-term heart rhythm monitoring (7 days) or a control group without long-term ECG monitoring (2,000 in each group). Individuals with AF in the intervention group will be offered anticoagulation therapy in accordance with current guidelines. The intervention group and the control group will be compared with regards to incident stroke and death within a 6-year follow-up period. Information on endpoints and anticoagulation use will be obtained through linkage to national registries.