Assessing improvements in survival for stroke patients in the Northern Territory 1992-2013: a marginal structural analysis.

OBJECTIVE: The aim of the present study was to investigate changes in stroke survival among Indigenous and non-Indigenous patients in the Northern Territory (NT). METHODS: A longitudinal study was undertaken of stroke patients admitted to NT public hospitals between 1992 and 2013. The Kaplan-Meier method and proportional hazards regression were used for survival analysis. A marginal structural model was applied to adjust for time-dependent confounders and informative censoring. RESULTS; There were 4754 stroke in-patients over the period, with 3540 new cases and 837 stroke deaths. Mean age of onset for Indigenous patients (51.7 years) was 12.3 years younger than that for non-Indigenous patients. After adjustments for confounders and loss to follow-up, in-hospital deaths were more likely among Indigenous patients (hazard ratio (HR) = 1.56; P < 0.01) and less likely among males (HR = 0.86; P < 0.05) and patients from remote areas (HR = 0.72; P < 0.01). There was a 3% decrease annually in mortality hazard from 1992 to 2013. Renal disease, cancer and chronic obstructive pulmonary disease had deleterious effects on stroke survival. CONCLUSIONS: Stroke survival has improved in the NT over the past two decades. The marginal structural models provide a powerful methodological tool that can be applied to hospital administrative data to assess changes in quality of care and the impact of interventions.

Health inequity in the Northern Territory, Australia.

INTRODUCTION: Understanding health inequity is necessary for addressing the disparities in health outcomes in many populations, including the health gap between Indigenous and non-Indigenous Australians. This report investigates the links between Indigenous health outcomes and socioeconomic disadvantage in the Northern Territory of Australia (NT). METHODS: Data sources include deaths, public hospital admissions between 2005 and 2007, and Socio-Economic Indexes for Areas from the 2006 Census. Age-sex standardisation, standardised rate ratio, concentration index and Poisson regression model are used for statistical analysis. RESULTS: There was a strong inverse association between socioeconomic status (SES) and both mortality and morbidity rates. Mortality and morbidity rates in the low SES group were approximately twice those in the medium SES group, which were, in turn, 50% higher than those in the high SES group. The gradient was present for most disease categories for both deaths and hospital admissions. Residents in remote and very remote areas experienced higher mortality and hospital morbidity than non-remote areas. Approximately 25-30% of the NT Indigenous health disparity may be explained by socioeconomic disadvantage. CONCLUSIONS: Socioeconomic disadvantage is a shared common denominator for the main causes of deaths and principal diagnoses of hospitalisations for the NT population. Closing the gap in health outcomes between Indigenous and non-Indigenous populations will require improving the socioeconomic conditions of Indigenous Australians.

A multilevel analysis on the relationship between neighbourhood poverty and public hospital utilization: is the high Indigenous morbidity avoidable?

BACKGROUND: The estimated life expectancy at birth for Indigenous Australians is 10-11 years less than the general Australian population. The mean family income for Indigenous people is also significantly lower than for non-Indigenous people. In this paper we examine poverty or socioeconomic disadvantage as an explanation for the Indigenous health gap in hospital morbidity in Australia. METHODS: We utilised a cross-sectional and ecological design using the Northern Territory public hospitalisation data from 1 July 2004 to 30 June 2008 and socio-economic indexes for areas (SEIFA) from the 2006 census. Multilevel logistic regression models were used to estimate odds ratios and confidence intervals. Both total and potentially avoidable hospitalisations were investigated. RESULTS: This study indicated that lifting SEIFA scores for family income and education/occupation by two quintile categories for low socio-economic Indigenous groups was sufficient to overcome the excess hospital utilisation among the Indigenous population compared with the non-Indigenous population. The results support a reframing of the Indigenous health gap as being a consequence of poverty and not simplistically of ethnicity. CONCLUSIONS: Socio-economic disadvantage is a likely explanation for a substantial proportion of the hospital morbidity gap between Indigenous and non-Indigenous populations. Efforts to improve Indigenous health outcomes should recognise poverty as an underlying determinant of the health gap.

Projecting demands for renal replacement therapy in the Northern Territory: a stochastic Markov model.

Objective The aim of the present study was to evaluate the potential effects of different health intervention strategies on demand for renal replacement therapy (RRT) services in the Northern Territory (NT). Methods A Markov chain simulation model was developed to estimate demand for haemodialysis (HD) and kidney transplantation (Tx) over the next 10 years, based on RRT registry data between 2002 and 2013. Four policy-relevant scenarios were evaluated: (1) increased Tx; (2) increased self-care dialysis; (3) reduced incidence of end-stage kidney disease (ESKD); and (4) reduced mortality. Results There were 957 new cases of ESKD during the study period, with most patients being Indigenous people (85%). The median age was 50 years at onset and 57 years at death, 12 and 13 years younger respectively than Australian medians. The prevalence of RRT increased 5.6% annually, 20% higher than the national rate (4.7%). If current trends continue (baseline scenario), the demand for facility-based HD (FHD) would approach 100000 treatments (95% confidence interval 75000-121000) in 2023, a 5% annual increase. Increasing Tx (0.3%), increasing self-care (5%) and reducing incidence (5%) each attenuate demand for FHD to ~70000 annually by 2023. Conclusions The present study demonstrates the effects of changing service patterns to increase Tx, self-care and prevention, all of which will substantially attenuate the growth in FHD requirements in the NT. What is known about the topic? The burden of ESKD is projected to increase in the NT, with demand for FHD doubling every 15 years. Little is known about the potential effect of changes in health policy and clinical practice on demand. What does this paper add? This study assessed the usefulness of a stochastic Markov model to evaluate the effects of potential policy changes on FHD demand. What are the implications for practitioners? The scenarios simulated by the stochastic Markov models suggest that changes in current ESKD management practices would have a large effect on future demand for FHD.

Stroke incidence and case-fatality among Indigenous and non-Indigenous populations in the Northern Territory of Australia, 1999-2011.

BACKGROUND: Stroke is a leading cause of death and disability in Australia. The impact of stroke on the Australia Indigenous people is, however, unclear. AIM: This study describes hospital-based stroke incidence and case fatality in the Northern Territory population in Australia. METHODS: Retrospective study of Northern Territory residents with a first-ever stroke episode and case fatality among Northern Territory residents in 1999-2011. RESULTS: The rate ratio of age-adjusted stroke incidence between Indigenous and non-Indigenous populations was 2·8 for men and 2·7 for women, similar to those reported elsewhere in Australia. The rate ratio increased to 3·8 (95% confidence interval: 3·4-4·3) after adjusting for multiple risk factors. There was no change in annual incidence between 1999 and 2011 for either non-Indigenous (incidence rate ratio per year 1·01, 95% confidence interval: 1·00-1·03) or Indigenous people (incidence rate ratio: 1·00, 95% confidence interval: 0·98-1·02), although incidence did increase for non-Indigenous people in the 15-39 year age group (incidence rate ratio: 1·09, 95% confidence interval: 1·02-1·17) and for Indigenous people in the 40-64 year age group (incidence rate ratio: 1·03, 95% confidence interva1·00-1·06). The case fatality rate decreased from 22% in 1999 to 12% in 2011. In-hospital deaths were more common among; older and Indigenous people, for those with other chronic diseases, and from haemorrhagic stroke compared with ischemic stroke. CONCLUSIONS: In the Northern Territory, as elsewhere in Australia, Indigenous Australians are more likely than other Australians to suffer a stroke. Lack of falling in incidence in the Northern Territory population highlights the importance for ongoing comprehensive primary and acute care in reducing risk factors and managing stroke patients.

Adverse outcome after incident stroke hospitalization for Indigenous and non-Indigenous Australians in the Northern Territory.

BACKGROUND: Survival after a stroke is lower for Indigenous than other stroke patients in Australia. It is not known whether recurrence is more common for Indigenous patients, or whether their higher prevalence of comorbidity affects their lower survival. AIMS: This study aimed to investigate the stroke recurrence and role of comorbidities in adverse stroke outcomes (recurrence and death) for Indigenous compared with other Australians. METHODS: A retrospective cohort study of first hospitalization for stroke (n = 2105) recorded in Northern Territory hospital inpatient data between 1996 and 2011 was conducted. For the multivariable analyses of adverse outcomes, logistic regression was used for case fatality and competing risk analysis for recurrent stroke and long-term death. Comorbidities (identified from inpatient diagnosis data) were analyzed using the Charlson Comorbidity Index (modified for stroke outcomes). RESULTS: Prevalence of comorbidities, case fatality, incidence of re-hospitalization for recurrent stroke, and long-term death rate were higher for Indigenous than non-Indigenous stroke patients. Adjustment for comorbidity in multivariable analyses considerably reduced Indigenous patients' excess risk for case fatality (odds ratio: 1·25, 0·88-1·78) and long-term death (standard hazard ratio: 1·27, 1·01-1·61) (but not recurrence), implying that their excess risk of death was in part due to higher comorbidity prevalence. CONCLUSION: Indigenous stroke patients have higher prevalence of comorbidities than non-Indigenous stroke patients, which explained part of the disparity in both case fatality and long-term survival but did not explain the disparity in stroke recurrence at all.

Living longer with a greater health burden--changes in the burden of disease and injury in the Northern Territory Indigenous population between 1994-1998 and 1999-2003.

OBJECTIVE: To measure changes over time in the burden of disease for Northern Territory (NT) Indigenous and non-Indigenous population. METHODS: The numbers, and crude and age-adjusted rates of disability adjusted life years (DALY) were calculated for periods 1994-1998 and 1999-2003. A measure of information bias was developed to adjust for the tendency of years lost to disability (a component of DALY) to increase over time because of increasing data availability. The jackknife method was used for DALY uncertainty assessment. RESULTS: The all-cause DALY rate was stable for the non-Indigenous population, but increased for the Indigenous population. For both populations, the burden of premature death decreased while the burden of disability increased. For the Indigenous population, there were substantial increases in DALY rates for type 2 diabetes, depression, nephritis/nephrosis, suicide and sense organ disorders. CONCLUSIONS: The burden of disease for Indigenous people increased over the study periods, with improvement in the burden of fatal outcomes more than offset by substantial increase in the prevalence and severity of non-fatal conditions. IMPLICATIONS: The paradoxical shift of living longer with a greater health burden has not been previously reported for Indigenous Australians, and highlights the critical importance of prevention for sustaining life expectancy improvement and managing escalation of health costs. This study also demonstrated the usefulness of the DALY to monitor population health.

Incidence and survival after acute myocardial infarction in Indigenous and non-Indigenous people in the Northern Territory, 1992-2004.

OBJECTIVE: To estimate the incidence and survival rates of acute myocardial infarction (AMI) for Northern Territory Indigenous and non-Indigenous populations. DESIGN AND PARTICIPANTS: Retrospective cohort study for all new AMI cases recorded in hospital inpatient data or registered as an ischaemic heart disease (IHD) death between 1992 and 2004. MAIN OUTCOME MEASURES: Population-based incidence and survival rates by age, sex, Indigenous status, remoteness of residence and year of diagnosis. RESULTS: Over the 13-year study period, the incidence of AMI increased 60% in the NT Indigenous population (incidence rate ratio [IRR], 1.04; 95% CI, 1.02-1.06), but decreased 20% in the non-Indigenous population (IRR, 0.98; 95% CI, 0.97-1.00). Over the same period, there was an improvement in all-cases survival (ie, survival with and without hospital admission) for the NT Indigenous population due to a reduction in deaths both pre-hospital and after hospital admission (death rates reduced by 56% and 50%, respectively). The non-Indigenous all-cases death rate was reduced by 29% as a consequence of improved survival after hospital admission; there was no significant change in pre-hospital survival in this population. Important factors that affected outcome in all people after AMI were sex (better survival for women), age (survival declined with increasing age), remoteness (worse outcomes for non-Indigenous residents of remote areas), year of diagnosis and Indigenous status (hazard ratio, 1.44; 95% CI, 1.21-1.70). CONCLUSIONS: Our results show that the increasing IHD mortality in the NT Indigenous population is a consequence of a rise in AMI incidence, while at the same time there has been some improvement in Indigenous AMI survival rates. The simultaneous decrease in IHD mortality in NT non-Indigenous people was a result of reduced AMI incidence and improved survival after AMI in those admitted to hospital. Our results inform population-specific strategies for a systemwide response to AMI management.

End-stage renal disease in the Northern Territory: current and future treatment costs.

OBJECTIVE: To compare hospital costs of Aboriginal and non-Aboriginal patients having haemodialysis treatment and forecast the future treatment cost. METHODS: The costs of patients with HD in the "Top End" of Australia's Northern Territory were estimated for the financial years 1996/97 and 1997/98 using a hospital costing model. We used an Autoregression Integrated Moving Average model to predict future demand. RESULTS: 165 patients (101 Aboriginal and 64 non-Aboriginal) were treated at a total cost of $12.4 million in this two-year period. These 165 patients represented 0.7% of inpatients, 8.8% of total inpatient costs and 31.6% of total inpatient episodes of care in the Top End region. $9.5 million (77%) was spent on routine haemodialysis treatment and $2.9m (23%) on other hospitalisations. The average cost per routine haemodialysis treatment over the two-year period was $527, or $78 600 per patient treatment year. Hospitalisations for comorbidities occurred in 86% of Aboriginal and 39% of non-Aboriginal patients. Average cost per patient, number of admissions and length of hospital stays were all significantly greater for Aboriginals. We predict an average increase in the number of treatments of 12% each year over the next five years and a five-year cost of $49.8m. CONCLUSIONS: A multipronged strategy designed to reduce the prevalence and costs of renal failure is required.