Subarachnoid haemorrhage in Sweden 1987-2002: regional incidence and case fatality rates

Background: Incidence estimates of subarachnoid haemorrhage (SAH) in Sweden vary, which may be caused by regional variations. Reliable estimates of age-specific case fatality rates are lacking. We analysed regional incidence rates and case fatality rates of SAH in Sweden. Methods: The Swedish Hospital Discharge and Cause of Death Registries from 1987 to 2002 yielded data on 18 443 patients with SAH. Incidence and case fatality rates by age, gender, region and time period were calculated by Poisson regression. Results: The incidence rate was 12.4 per 100 000 person-years (95% CI 12.2 to 12.6) and increased with age, from 6.4/100 000 person-years in patients who were 30-39 years old to 25.8/100 000 person-years in patients who were older than 80 years. Incidence was higher for women (14.4 (95% CI 14.2 to 14.7)) than for men (10.3 (95% CI 10.3 to 10.6)), and higher in the north than in the south (RR 1.31 (95% CI 1.25 to 1.37)). This geographical gradient was more evident in women (RR 1.41 (95% CI 1.33 to 1.49)) than in men (RR 1.23 (95% CI 1.15 to 1.33)). The 28-day case fatality rate was 31.7% (95% CI 31.0 to 32.3). It increased with age from 18.1% (95% CI 16.0 to 20.3) in patients who were 30-39 years old to 57.6% (95% CI 55.2 to 59.9) in patients over 80 years, then levelling off. Over time (1995-2002 compared with 1987-1994), the incidence rate decreased (RR 0.93 (95% CI 0.90 to 0.96)) and case fatality rate decreased (RR 0.89 (95% CI 0.85 to 0.93)). Conclusions: SAH incidence rates in Sweden increase from south to north, more in women than in men. Octogenarians have a quadrupled incidence and a tripled case fatality compared with young adults. During 16 years, both incidence and case fatality have decreased.