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 nonsignificant 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, foreignborn 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, allcause 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
