Coronary heart disease and migration : management, prognosis and health equity

Abstract

Background and aim: Coronary heart disease (CHD), the most common form of which is myocardial infarction (MI), is a significant health problem. In Sweden circulatory diseases account for 50% of total mortality; half of these are associated with CHD. The percentage of foreign-born in Sweden is about 16 % of the total population. Ethnic differences in disease and its outcomes have been widely reported internationally. This thesis was to increase understanding of the differences in utilization of health care by exploring the incidence and recurrence of MI, drug consumption after MI, prognosis after MI and coronary artery bypass graft (CABG) in relation to country of birth, socio-economic position (SEP) and gender.

Materials and methods: The data used in this thesis are from newly established Migration and Health Cohort specifically designed to address health status among immigrants in Sweden. The cohort is a linkage of several national registers. There were four studies. The study periods were 1987–2008 (Study I), 2006–2008 (Study II), 1987–2007 (Study III) and 1995 – 2007 (Study IV). The study populations were the total Swedish population (Study I), all first MI patients (Studies I, II and III) and all individuals who underwent a first isolated CABG (Study IV). The outcomes were incidence of and mortality after MI (Study I), drug use after MI (Study II), recurrent MI (Study III) and mortality after CABG respectively (Study IV). The potential confounders were age, sex, education, comorbidities, calendar years of follow-up, marital status and waiting time for surgery. We calculated incidence rate ratios (IRRs) and hazard ratios (HRs) (Studies I, III and IV) and odds ratios (ORs) (Study II) with 95% confidence intervals (CIs) in multivariable adjusted models using Poisson, Cox, and logistic regression models, respectively.

Results: We observed downward trends in first-time MI incidence and case fatality after day 28 for both sexes regardless of country of birth. The trends were, however, less pronounced among female and foreign-born subjects. Among those who did not used cardiovascular drugs before MI, we found no difference in drug use after MI by migration status in an adjusted model (OR 1.00, 95 % CI 0.89–1.12). Among those who used some but not all recommended cardiovascular drugs before MI, foreign-born cases had a non-significant slightly lower use of recommended drugs in the adjusted model (OR 0.92, 95 % CI 0.83–1.03). Among those with the lowest education level, foreign-born patients had a slightly lower use of recommended drug compared to Sweden-born patients. Women with a low SEP used fewer drugs after MI irrespective of country of birth (Study II). A downward trend in risk of second MI was found. However, regardless of country of birth, men had a higher risk of second MI than women (HR 1.14, 95% CI 1.12–1.55). Foreign-born men and women had a slightly increased HR than their Sweden- born counterparts. Foreign-born patients who had lived in Sweden for less than 35 years had a higher risk than those who had lived there for 35 years or longer (Study III). There was no significant difference in overall early or late mortality after CABG between foreign-born and Sweden-born patients in both sexes. However, all-cause mortality differed between some countries and was highest in foreign-born men from Eastern Africa (HR 3.80, 95% CI 1.58–9.17), China (HR 3.61, 95% CI 1.50–8.69) and Chile (HR 2.12, 95% CI 1.01–4.47) (Study IV). Patients with a low level of education had higher incidence of MI and worse prognosis after MI and CABG compared to those with longer than 12 years of education irrespective of sex and country of birth (Studies I, III and IV). This difference was more pronounced among foreign-born women.

Conclusion: A slightly increased incidence of and mortality after first MI, and risk of recurrent MI was found among foreign-born compared to Sweden-born individuals. Although the incidence of and mortality after first-time MI, and risk of recurrent MI, continued to decrease over time, low SEP, measured in terms of education level, independent of country of birth and sex, remained an important risk indicator for these events. There were no apparent differences in drug prescription after MI between foreign-born and Sweden-born patients. There were no differences in early and late mortality after isolated CABG. However, there was inequity in adequate secondary prevention therapy after MI between education groups regardless of country of birth.