Evidence of Stable Incidence of Aneurysmal Subarachnoid Haemorrhage in Tasmania, Australia Over the Last 20 Years

Objective: There have been few studies of the changes in incidence of aneurysmal subarachnoid haemorrhage (aSAH). The most recent study, conducted in the UK, reported that incidence had not changed between 1981-84 and 2001-04. Recent changes in population distribution of risk factors for aSAH warrant updated incidence studies.

Methods: A retrospective study capturing all cases of aSAH across the island state of Tasmania, Australia (population 515,000) that has a single neurosurgical unit. Between 2010-14, potential cases of aSAH were identified using keyword medical record searches of admission and discharge lists. The 1996 Australian census population aged > 15 years was used for calculation of age standardized rates (ASR per 100, 000) and 95% confidence intervals to allow comparison with a previously published estimates of incidence from 1995-98.

Results: There were 1012 potential cases of aSAH identified from the multiple sources with 175 incident cases identified (66.9% female, Age 58.32 ± 16.14 years). The crude overall rate was 8.40 per 100,000 (5.65 in males, 11.09 in females). ASRs per 100,000 were 7.15 (95% Cl: 4.02, 10.29) overall, 4.92 (95% CI: 3.28, 5.90) in males and 9.36 (95% CI: 7.59, 11.13) in females. These were marginally lower than ASR per 100,000 reported in 1995-98: overall 8.9; males 6.7; females 10.9.

Conclusions: Incidence of aSAH has remained relatively unchanged Tasmania over 20 years, which is in contrast to other forms of stroke. This may be explained by concurrent decreases in some risk factors, such as smoking, but increases in other risk factors, such as diabetes. Efforts to reduce the incidence of aSAH should be promote, particularly given the poor outcomes associated with this disease.