[What do we know about the frequency of stroke? A review of incidence studies]

In Norway, mortality from stroke has declined during the last 30-40 years. It is unknown whether the frequency of stroke has declined. This article presents studies on incidence and trends in incidence of stroke in different countries, especially Scandinavian countries. Geographical differences in incidence are small, when the rates are compared, adjusted for age and sex. Time trend studies on incidence give conflicting results. Some studies suggest increasing incidence of stroke, others a decrease or even no change of incidence. The age-standardised incidence rate (adjusted to the Norwegian population) from six studies in people aged 55-84 years is estimated to 6-8 per 1,000 per year. Little is known about incidence and time trend in Norway. Factors of importance for primary prevention of stroke (e.g. treatment of hypertension), treatment and rehabilitation of the stroke patient and knowledge about the incidence.