Abstract and Introduction
Abstract
Background Marriage is associated with lower risk of coronary heart disease, but it is unknown if the association depends on time since break-up with a partner. In this study we included both married and unmarried couples to study if the association between broken partnership (BP) and first time incident myocardial infarction (MI) changes with time since BP.
Methods Register study of the entire Danish population: the population was restricted to those aged 30 to 65 years with follow-up for incident MI between 1985 and 2006 with an annual record on each individual; in total 43 million records. The register data were used to identify MI events. Poisson regression was used to study associations between time since BP and MI adjusted for socio-demographic confounders and hospital admissions. Analyses were stratified by sex.
Results Compared with unexposed (no BP), the incidence rate ratio (IRR) of MI in men with BP in the same year was 0.97 [95% confidence interval (CI) 0.90–1.05], year before BP was 1.25 (95% CI 1.17–1.34), 2–3 years after BP was 1.12 (95% CI 1.06–1.18), 4–8 years after BP was 1.09 (95% CI 1.05–1.14) and 9+ years since BP was 1.09 (95% CI 1.05–1.12). In women, the IRR same year as BP was 1.45 (95% CI 1.26–1.66), the year after BP was 1.30 (95% CI 1.14–1.50), 2–3 years after BP was 1.26 (95% CI 1.13–1.39), 4–8 years after BP was 1.17 (95% CI 1.08–1.26) and 9+ years since BP was 1.24 (95% CI 1.17–1.32).
Conclusions We found both a short-term elevated risk of first time MI following BP and a weaker long-term elevated risk, in both men and women.
Introduction
During the past few decades changes in family life have lead to an increase in divorce and to more people living alone or in unmarried unions. However, although divorce has become more common and arguably more socially accepted, the difference in health between the married and the unmarried seem to have grown. Breaking up with a partner is a common experience in adult life and it is important to investigate its immediate and long-term health consequences.
Several studies have demonstrated that marriage is protective against coronary heart disease (CHD) mortality and the results almost consistently show a higher mortality among divorced and widowed people. The association between marital status and cardiovascular mortality may be due to a lower incidence among married individuals or due to better survival among the married with cardiovascular disease. Fewer studies have investigated the association between marital status and incident CHD. In a study of Finnish middle-aged men, Koskenvuo et al. found a higher incidence of CHD in the divorced and widowed compared with the married but a lower incidence in singles. In a population of Australian men, Malcolm and Dobson found that the widowed and divorced but not the never married had an increased risk of acute myocardial infarction (MI) or of sudden coronary death compared with the married. Two studies on Swedish men found excess risk of fatal and non-fatal MI in non-cohabiting men and association between being never married or divorced and non-fatal MI. However, Mendes de Leon et al. found no significant association between marital status and fatal and non-fatal MI among middle-aged men. Only one previous study on the association between marital status and incident MI included women and this study found stronger association between marital status and MI in women compared with men, which suggests that the association between divorce and MI may differ between men and women. These studies have all studied marital status as a stage which suggests that resources in marriage promote good health. An alternative approach is the stress model which would suggest that it is the change in marital status that has consequences for health. A break-up of a romantic relationship has been rated as one of the most stressful life events. Other studies have linked stressful life events to CHD and MI. Death of a spouse has been related to CHD mortality and death of a child has been related to incident MI several years after the exposure. Death of a sibling was related to MI a few years after the exposure. Broken partnership is common in adult life but it is unknown how this is related to incident MI and how this association may vary with time since broken partnership. In this paper, we set out to study the stress model and hence focus on consequences of breaking up a romantic relationship.
Most previous studies used official marital status. However, in populations (such as the Danish) where unmarried cohabitation is common, relying on official marital status would imply that many unmarried individuals who are cohabiting are misclassified as 'single'. Further, when the focus is on change in intimate relationships with a partner, it is an advantage to use change in cohabitation status, because moving apart most commonly precedes divorce. Throughout this paper we use the terms marriage, marital status and divorce when we refer to studies which used official marital status. The term broken partnership refers to breaking an intimate relationship regardless of marital status, which is the focus of the present study.
The aim of this study was to investigate if the association between broken partnership and first time incident fatal and non-fatal MI depends on time since broken partnership in a population of men and women who were initially cohabiting with a partner and free of earlier MI at baseline, and if any associations differ between men and women and in different age groups.