Changing rates of stroke in the province of Quebec, Canada: 1981-1988

Using more than 37,000 hospital discharges attributed to hemorrhagic or occlusive stroke in the province of Quebec, Canada, we analyzed trends in stroke incidence during the period 1981-1988. There were large and statistically significant (p less than 0.05) increases in the rates of hemorrhagic stroke over this period. Dramatic increases occurred among men in the rates of both intracerebral (International Classification of Diseases--Ninth Revision [ICD9] code 431) and intracranial (ICD9 code 432) hemorrhagic strokes (40-204% depending on age). In contrast, the rates of occlusion of the precerebral arteries (ICD9 code 433) declined in younger men and women but increased substantially (107%) in older men. Rates of occlusion of the cerebral arteries (ICD9 code 434) declined in men over the age of 50 years and in women aged 50-79 years. Despite the decline in the rate of occlusion of the cerebral arteries, the rate of hemorrhagic stroke appears to have increased. Changes in the hospitalization rates for hemorrhagic stroke were not accompanied by consistent decreases in the case-fatality rate. This finding tends to support the hypothesis of an actual increase in the hospitalization rate fo hemorrhagic stroke rather than an artifactually elevated rate due to enhanced diagnosis by computed tomography.