Declining trends in incidence, case-fatality and mortality of stroke in three geographic areas of Finland during 1983-1989. Results from the FINMONICA stroke register.

Stroke mortality has decreased during the last decade in many industrialized countries, but there has been no clear evidence for a decline in the incidence of stroke. The present study analyzes the trends in the incidence, mortality and case-fatality of stroke in Finland from 1983 to 1989. We used data from the FINMONICA stroke register, a community based register collecting information on all suspected stroke cases aged 25-74 in three geographical areas of Finland. Annual attack rate, incidence, mortality and case-fatality rates were calculated for all strokes and for different subcategories of stroke. A linear regression model was applied to calculate the yearly trends of these rates. In men, the attack rate of stroke was 336/100,000 in 1983 and 310/100,000 in 1989 (-8% during the observation period); incidence declined from 269/100,000 in 1983 to 236/100,000 in 1989 (-12%); mortality declined from 82/100,000 to 64/100,000 (-22%), and case-fatality declined from 25% to 21% (-18%). Also among women similar declining trends were observed (-11%, -13%, -16%, and -10% respectively), but they were not statistically significant. In both incidence and mortality of stroke, the decline was seen in all age groups. Incidence and mortality of cerebral infarction declined similarly to all strokes. A large fall in the incidence (-24% in both men and women) and mortality (-38% in men and -27% in women) of subarachnoid haemorrhage was also observed. An increasing trend, although not significant, was instead observed for cerebral haemorrhage. First stroke and especially first cerebral infarction contributed most to the decline in case-fatality. The availability of computerized brain tomography improved from 18% in 1983 to 60% in 1989. We observed a fall in the incidence, mortality, and case-fatality of stroke during 1983-1989. Among the subtypes of stroke, cerebral infarction contributed most to the decline, but the data suggested also a declining trend in the incidence and mortality of subarachnoid haemorrhage, observed now for the first time in Finland since the 1960s. The fall in the incidence of stroke was not as steep during the 1980s as it was during the 1970s; Finland is anyhow the only European country which has reported a decreasing trend in stroke incidence during the 1980s. We need now to investigate how much the decline in the classical risk factors for stroke observed in Finland during the last two decades predicts the observed trends.