Record linked retrospective cohort study of 4.6 million people exploring ethnic variations in disease: myocardial infarction in South Asians

Abstract

BackgroundLaw and policy in several countries require health services to demonstrate that they are promoting racial/ethnic equality. However, suitable and accurate data are usually not available. We demonstrated, using acute myocardial infarction, that linkage techniques can be ethical and potentially useful for this purpose.MethodsThe linkage was based on probability matching. Encryption of a unique national health identifier (the Community Health Index (CHI)) ensured that information about health status and census-based ethnicity could not be ascribed to an identified individual. We linked information on individual ethnic group from the 2001 Census to Scottish hospital discharge and mortality data.ResultsOverall, 94% of the 4.9 million census records were matched to a CHI record with an estimated false positive rate of less than 0.1 %, with 84.9 – 87.6% of South Asians being successfully linked. Between April 2001 and December 2003 there were 126 first episodes of acute myocardial infarction (AMI) among South Asians and 30,978 among non-South Asians. The incidence rate ratio was 1.45 (95% CI 1.17, 1.78) for South Asian compared to non-South Asian men and 1.80 (95% CI 1.31, 2.48) for South Asian women. After adjustment for age, sex and any previous admission for diabetes the hazard ratio for death following AMI was 0.59 (95% CI 0.43, 0.81), reflecting better survival among South Asians.ConclusionThe technique met ethical, professional and legal concerns about the linkage of census and health data and is transferable internationally wherever the census (or population register) contains ethnic group or race data. The outcome is a retrospective cohort study. Our results point to increased incidence rather than increased case fatality in explaining high CHD mortality rate. The findings open up new methods for researchers and health planners.

Differences between immigrants at various durations of residence and host population in all-cause mortality, Canada 1991–2006

“…First, the matching success rate of 80 per cent for the 1991 Census Mortality and Cancer Follow-up Study is consistent with matching results from other countries (e.g., Blackwell et al 2003;Borrell et al 2003;Spoerri et al 2006;Fischbacher et al 2007;Hajat et al 2010). Further, 99 per cent of the matched records in our data were determined to be valid, that is, the matching was to the correct person.…”

Outcomes After Acute Myocardial Infarction in South Asian, Chinese, and White Patients

“…5,27,39 Cardiac mortality for a population is dependent on the prevalence of cardiac disease and mortality from cardiac disease. The higher age-standardized cardiac mortality in the South Asian population is more likely driven by their higher prevalence of coronary disease and AMI 10,39 rather than a higher AMI case fatality. Furthermore, some of the studies identifying a higher cardiac mortality originate from the United Kingdom, which has a significant Pakistani and Bangladeshi South Asian population.…”

“…9 South Asian patients have a disproportionately higher burden of predisposing cardiac risk factors, including insulin resistance and dyslipidemia, and notably higher incidence rates of acute myocardial infarction (AMI). 10 International studies also document a substantially lower incidence of AMI in Chinese populations. 1 …”

Epidemiology and disease burden from allergic disease in Scotland: analyses of national databases

“…Given the lack of data on ethnicity, it is important to consider bridging this gap using the data linkage techniques recently developed by Bhopal et al, 27 which allow linkage of healthcare records with census ethnicity codes using a probabilistic matching technique. Similarly, to obtain a broader picture of costs to society associated with allergic disorders, it is important to consider, for example, the impact on school and work performance, 28 and this should also prove possible with greater investment in data-linkage techniques.…”