Trends in stroke incidence in Auckland, New Zealand, during 1981 to 2003

Background and Purpose - Long-term trends in stroke incidence in different populations have not been well characterized, largely as a result of the complexities associated with population-based stroke surveillance. Methods - We assessed temporal trends in stroke incidence using standard diagnostic criteria and community-wide surveillance procedures in the population (approximate to 1 million) of Auckland, New Zealand, over 12-month calendar periods in 1981 - 1982, 1991 - 1992, and 2002-2003. Age-adjusted first-ever (incident) and total (attack) rates, and temporal trends, were reported with 95% confidence intervals (CIs). Rates were analyzed by sex and major age groups. Results - From 1981 to 1982, stroke rates were stable in 1991 - 1992 and then declined in 2002 - 2003, to produce overall modest declines in standardized incidence (11%; 95% CI, 1 to 19%) and attack rates (9%; 95% CI, 0 to 16%) between the first and last study periods. Some favorable downward trends in vascular risk factors such as cigarette smoking were counterbalanced by increasing age and body mass index, and frequency of diabetes, in patients with stroke. Conclusions - There has been a modest decline in stroke incidence in Auckland over the last 2 decades, mainly during 1991 to 2003, in association with divergent trends in major risk factors.