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

Background and Purpose - Although geographical variations in stroke rates are well documented, limited data exist on temporal trends in ethnic-specific stroke incidence. Methods - We assessed trends in ethnic-specific stroke rates using standard diagnostic criteria and community-wide surveillance procedures in Auckland, New Zealand (NZ) in 1981 to 1982, 1991 to 1992, and 2002 to 2003. Indirect and direct methods were used to adjust first-ever (incident) and total (attack) rates for changes in the structure of the population and reported with 95% CIs. Ethnicity was self-defined and categorized as "NZ/ European," "Maori," " Pacific peoples," and " Asian and other." Results - Stroke attack (19%; 95% CI, 11% to 26%) and incidence rates (19%; 95% CI, 12% to 24%) declined significantly in NZ/Europeans from 1981 to 1982 to 2002 to 2003. These rates remained high or increased in other ethnic groups, particularly for Pacific peoples in whom stroke attack rates increased by 66% (95% CI; 11% to 225%) over the periods. Some favorable downward trends in vascular risk factors, such as cigarette smoking, were counterbalanced by increasing age, body mass index, and diabetes in certain ethnic groups. Conclusions - Divergent trends in ethnic-specific stroke incidence and attack rates, and of associated risk factors, have occurred in Auckland over recent decades. The findings provide mixed views as to the future burden of stroke in populations undergoing similar lifestyle and structural changes.