Downward trend in the risk of second myocardial infarction in Sweden, 1987-2007: breakdown by socioeconomic position, gender, and country of birth.

Background: Second myocardial infarction (SMI) is a significant health problem. There are no nationwide studies on SMI among foreign-born populations that include detailed information about country of birth.
Design: Nationwide cohort study of 331,748 men and 186,755 women aged 30-84, living in Sweden, and diagnosed with first myocardial infarction (FMI) between January 1987 and December 2007.
Methods: Trends in, and risk of, SMI after day 28 of FMI association with gender, educational level, and country of birth were analysed. A hazard ratio (HR) with a 95% confidence interval (CI) yielded a risk estimate of SMI among FMI patients based on the Cox proportional hazard model.
Results: Men had a higher risk of SMI than women (HR 1.14, 95% CI 1.12-1.55) with a downward trend over time, regardless of country of birth (p-trend <0.0001). Low educational level increased the HR of SMI irrespective of gender or country of birth. Foreign-born men and women had a slightly increased HR than Sweden-born. Men born in India, Palestine, Uganda, Algeria, and Tunisia and women born in India, Palestine, and Lebanon had approximately a 2-fold risk. Men born in the Netherlands had the lowest risk (HR 0.65, 95% CI 0.44-0.94). Foreign-born who had lived in Sweden for less than 35 years had a higher risk than those that had lived there for 35 years or longer.
Conclusions: Although the risk of SMI continued to decrease over time, low socioeconomic position independent of country of birth and gender remained an important risk indicator deserving further attention.