Coronary Mortality in South Asians: Aetiologic and Prognostic Effects (CALIBER)

Coronary death rates among first-generation migrants from South Asia are higher than those of the White majority population. Understanding the relative contribution of incidence and case fatality to overall coronary death rates allows preventive interventions to be targeted where they are likely to be more efficacious.

We seek to do this by meta-analysing new data with previously published work identified after systematic review of published literature. We will combine studies spanning different modes of presentation with coronary disease from 'normal' populations to suspected stable angina to higher-risk patients diagnosed with ACS within a national registry [MINAP].

Initially we will undertake retrospective cohort studies using four new databases (The aetiologic healthy population study, the Whitehall II Study; The chest pain clinic cohort with new-onset chest pain; the coronary angiography cohort (ACRE) and an acute coronary syndrome cohort, the Myocardial Infarction National Audit Project (MINAP).

We will define ethnicity according to the UK Office for National Statistics 1991 census categories. All four cohorts are flagged for mortality with the Office for National Statistics.

We will use a combined non-fatal outcome (non-fatal myocardial infarction and admission with angina) in the aetiologic cohort, as well as risk of coronary death. We will assess risk of coronary death in the chest pain clinic and coronary angiogram cohorts and all-cause death in the acute coronary syndrome cohort as cause-specific death is unavailable. We will assess prognosis for coronary death in Whitehall-II among those who had had typical angina at baseline. We will perform Cox proportional hazards regression adjusted for age (as a continuous variable), sex, hypertension, blood cholesterol, smoking and diabetes in all cohorts. We will then stratify these analyses in our prognostic studies by age, diabetes, ACS type, deprivation, smoking and secondary prevention management and formally examine whether a statistical difference exists between the hazard ratio of strata with the Bland-Altman two-tailed test of interaction.

We will combine results of new and older studies and calculate pooled odds ratios, weights, and 95% confidence intervals using a random effects model. Heterogeneity will be examined using the I2 statistic.