Excess stroke incidence in young Aboriginal people in South Australia: Pooled results from two population-based studies.

Background Retrospective data indicate increased stroke incidence in Aboriginal/Torres Strait Islander (Indigenous) Australians, possibly with poorer outcomes. We present the first prospective population-based stroke incidence study in Indigenous Australians. Methods We pooled data from ASCEND and SEARCH, two prospective "ideal" South Australian stroke incidence studies, ASCEND conducted in urban Northwestern Adelaide (2009-2010) and SEARCH in five South Australian rural centers (2009-2011). We calculated age-standardized incidence for Aboriginal and non-Aboriginal people. Results The study population comprised 261,403 inhabitants. Among 432 first-ever strokes, 13 were in Aboriginal people (median age 51 vs. 78 years for non-Aboriginal people, p < 0.001). Age-standardized stroke incidence per 100,000 in Aboriginal patients (116, 95% CI: 95-137) was nearly two-fold that of non-Aboriginal patients (67, 95% CI: 51-84). Age-stratified excess incidence in Aboriginal people was restricted to those aged < 55 years (incidence rate ratio (IRR) 3.5, 95% CI: 2-7), particularly for intracerebral hemorrhage (IRR: 16, 95% CI: 4-61). Conclusion The excess stroke incidence in Aboriginal South Australians appears substantial, especially in those aged <55 years. Further work is required to delineate and address disparities.

Stroke Epidemiology in an Australian Rural Cohort (SEARCH).

Background Stroke rates in Australia and New Zealand have been declining since 1990 but all studies have been completed in large urban centers. Aim We report the first Australasian stroke incidence study in a rural population. Methods The authors applied the principle of complete ascertainment, used the WHO standard definition of stroke and classified ischemic stroke by the TOAST criteria. Data were collected from five rural centers defined by postcode of residence, over a 2-year period with 12 months of follow up of all cases. Results There were 217 strokes in 215 individuals in a population of 96,036 people, over 2 years, giving a crude attack rate of 113 per 100,000 per year. The 181 first-ever strokes (83% of total), standardized to the WHO world population, occurred at a rate of 50/100,000 (95% CI: 43-58). The 28-day fatality for first-ever strokes was 24% (95% CI: 18-31) and 77% (95% CI: 71-83) were classified as ischemic (140/181), 15% (95% CI: 10-21) intracerebral hemorrhage, 3% (95% CI: 1-6) due to subarachnoid hemorrhage and 5% (95% CI: 2-9) were unknown. A high proportion of first-ever ischemic strokes (44%) were cardioembolic, mostly (77%) due to atrial arrhythmias. Of the 38 with known atrial arrhythmias prior to stroke, only six (16%) were therapeutically anticoagulated. Conclusions This rural companion study of a recent Australian urban stroke incidence study confirms the downward trend of stroke incidence in Australia, and reiterates that inadequate anticoagulation of atrial arrhythmia remains a preventable cause of ischemic stroke.

Abdominal adiposity and obstructive airway disease: testing insulin resistance and sleep disordered breathing mechanisms.

BACKGROUND: This study examined associations of abdominal adiposity with lung function, asthma symptoms and current doctor-diagnosed asthma and mediation by insulin resistance (IR) and sleep disordered breathing (SDB). METHODS: A random sample of 2500 households was drawn from the community of Whyalla, South Australia (The Whyalla Intergenerational Study of Health, WISH February 2008 - July 2009). Seven-hundred twenty-two randomly selected adults (≥18 years) completed clinical protocols (32.2% response rate). Lung function was measured by spirometry. Post-bronchodilator FEV1/FVC was used to measure airway obstruction and reversibility of FEV1 was calculated. Current asthma was defined by self-reported doctor-diagnosis and evidence of currently active asthma. Symptom scores for asthma (CASS) and SDB were calculated. Intra-abdominal fat (IAF) was estimated using dual-energy x-ray absorptiometry (DXA). IR was calculated from fasting glucose and insulin concentrations. RESULTS: The prevalence of current doctor-diagnosed asthma was 19.9% (95% CI 16.7 - 23.5%). The ratio of observed to expected cases given the age and sex distribution of the population was 2.4 (95%CI 2.1, 2.9). IAF was not associated with current doctor-diagnosed asthma, FEV1/FVC or FEV1 reversibility in men or women but was positively associated with CASS independent of IR and SDB in women. A 1% increase in IAF was associated with decreases of 12 mL and 20 mL in FEV1 and FVC respectively in men, and 4 mL and 7 mL respectively in women. SDB mediated 12% and 26% of these associations respectively in men but had minimal effects in women. CONCLUSIONS: In this population with an excess of doctor-diagnosed asthma, IAF was not a major factor in airway obstruction or doctor-diagnosed asthma, although women with higher IAF perceived more severe asthma symptoms which did not correlate with lower FEV1. Higher IAF was significantly associated with lower FEV1 and FVC and in men SDB mechanisms may contribute up to one quarter of this association.