Background: Monitoring temporal changes in the incidence of pathological stroke types (ischemic stroke [IS], intracerebral haemorrhage [ICH], and subarachnoid haemorrhage [SAH]) is important given their different risk factors, management, and prognoses. We report changes in these major stroke types between two Auckland Regional Community Stroke Studies (ARCOS).
Methods: ARCOS-IV (2010-2011) and ARCOS-V (2020-2021) are population-based studies of all new strokes in the Auckland region (aged >15 years) that captured the incidence of major pathological stroke types. Age-standardised incidence rate (per 100,000) ratios (IRR) with 95% confidence intervals (CIs) were calculated to assess temporal differences between studies by stroke type and ethnicity.
Results: In ARCOS-V, 1613 (78%) first-ever strokes were IS, 329 (16%) ICH, 110 (5%) SAH, and 9 (0.004%) undetermined. Between the two ARCOS studies, the IRR of IS (1.0 [95%CI 0.93-1.08]) showed no detectable change, while increases were observed in ICH (IRR=1.30 [1.09-1.55]) and SAH (IRR=1.11 [0.83-1.49]). Ethnic disparities were also observed with greater IRRs for ICH among Māori (1.91 [0.8-4.54]) and Pacific (1.61 [1.09-2.57]) peoples, and in SAH among Asian peoples (1.52 [0.72-3.20]). In ARCOS-V, Pacific peoples had the largest incidence of IS (143 [SE 0.1], followed by Māori (123 [0.1] while ICH was highest in Pacific (47 [SE 0.1]) (3.3-fold greater than in NZ Europeans).
Conclusions: Changes in stroke incidence varied by pathological types with increased rates for ICH and SAH but not IS. Māori and Pacific peoples had the largest rates and temporal increases in IS and ICH. Culturally appropriate primary prevention may reduce these disparities.