Subarachnoid hemorrhage (SAH) has a different epidemiological profile from other types of stroke and a different etiology. Although there has been a general decline in overall stroke incidence since the 1950s, secular trends for SAH have been modest. In contrast to other stroke types, changes in incidence over the last few decades have been less clear. The purpose of this study was to estimate hospitalization and case-fatality rates of SAH according to age, sex, calendar year, and season.
Data were obtained for each of Canada's 10 provinces for the 10 fiscal years 1982 through 1991. All hospitalizations of persons 15 years of age or older with a primary diagnosis at discharge coded 430 according to the International Classification of Diseases, 9th Revision, were included. Rates of SAH per 100,000 population were calculated for men and women for 5-year age groups, by calendar year, and by season. Annual age- and sex-specific (hospital) case-fatality rates up to 30 days were also calculated. Additionally, hospital deaths from this study were related to national SAH mortality statistics.
A total of 14145 women and 8995 men were discharged with a primary diagnosis of SAH during the 10-year period. In contrast to other types of stroke, the rates of SAH were higher for women than for men at all ages. The age-standardized rates of SAH in 1991-1992 were 11.2 per 100000 women and 8.0 per 100000 men. For women, there was a 6% (95% confidence interval [CI], -12% to 0%) decline in hospitalization rates over that period; for men, the decline was 15% (95% CI, -21% to -8%). The peak season for SAH among women was winter; for men the peaks were in the fall and spring. For both sexes, the lowest occurrence was in the summer. Over this period, 30-day case-fatality rates declined somewhat (statistically significant only in the age group of 35 to 44 years). The number of deaths enumerated from hospital discharges was 20% to 50% lower than the number recorded on national mortality statistics, indicating that a proportion of SAH deaths occurred before (or after) the hospital stay.
Although rates of hospitalization for SAH declined over this period, SAH remains an important neurological event affecting individuals at relatively young ages. The rates were higher for women than for men at all ages. Total (in-hospital) case-fatality rate remains high.