Incidence and outcome of subarachnoid haemorrhage: a retrospective population based study.

OBJECTIVES The purpose was to define the incidence and case fatality rates of subarachnoid haemorrhage in the population of Devon and Cornwall. METHODS A retrospective population based design was employed with multiple overlapping methods of case ascertainment. A strict definition of subarachnoid haemorrhage was used. Age and sex specific incidence rates and relative risks for death at different time intervals are calculated. RESULTS Eight hundred cases of first ever subarachnoid haemorrhage were identified; 77% of cases were verified by CT, 22% by necropsy, and 1% by lumbar puncture. The incidence rates are higher than those previously reported in the United Kingdom. The age standardised incidence rate (/100 000 person-years) for females was 11.9 (95% confidence interval (95% CI) 9.5-15.0), for males 7.4 (5.4-10.0), and the total rate was 9.7 (7.5-12.6). The case fatality rates at 24 hours, 1 week, and 30 days were 21 (18-24)%, 37 (33-41)%, and 44 (40-49)% respectively. The relative risk for death at 30 days for those over 60 years:under 60 years was 2.95 (2.18-3.97). CONCLUSION The incidence of subarachnoid haemorrhage in the United Kingdom is higher than previously reported. Three quarters of the mortality occurs within 3 days.