Changes in long-term survival after stroke in Auckland, New Zealand between 1981 and 1991, amongst those alive at 3 months

Abstract

Background. The Auckland Stroke Studies have previously demonstrated that differences in 3-month survival after stroke between 1981 and 1991 were explained by reduced severity at stroke onset. Long-term differences in stroke survival have not been adequately described. Method. Two large population-based studies of stroke in Auckland were conducted, with follow-up to 6 years. Long-term survival in those alive at 3 months was analysed using proportional hazards analysis, adjusted for demographics, severity, pre-stroke conditions and other factors, to explore the association of post-stroke survival with post-stroke care. Comparison with population-based data is also made. Results. Median survival time after stroke improved from 1.4 years in the 1981 cohort to 3.1 years in 1991. This is evident in a 43% reduced hazard (HR50.57, 95%CI 0.51 to 0.64) in 1991 even after adjustment for stroke severity and other factors. In those alive at 3 months, non-haemorrhagic stroke, demographic factors (increasing age, female sex, Maori or pacific ethnicity) and pre-stroke conditions (diabetes, and dependence in self-care) are the main non-modifiable predictors of death. Cigarette smoking is associated with 23% increased hazard (HR51.23, 95%CI 1.07 to 1.41). Referral to a neurologist is associated with 31% improved long-term survival (HR50.69, 95%CI 0.56 to 0.86). Discussion. Predictors of death early after stroke are different from those associated with later death. Reduced severity and changes in early care do not adequately account for the remaining improvement. Increased mean population life expectancy of 1.1 years over the same 10-year interval explains only part of the observed improvement in survival.