What accounts for the remaining 20 percent? An international team of researchers wanted to see whether one's marital status influences their risk of developing heart disease.
The researchers were led by Chun Wai Wong, who is a cardiovascular researcher at the University of Keele and the Academic Department of Cardiology at the Royal Stoke Hospital in Stoke-on-Trent, both in the United Kingdom.
The findings were published in the journal Heart.
A 42 percent higher risk for single people
To find out the influence of marital status on heart disease incidence, Wong and team examined 34 studies, summing up over 2 million participants, aged 42–77, from across the globe.
The researchers carried out a pooled analysis of these studies. The results showed that people who had never married, were divorced, or had been widowed were 42 percent more likely to develop cardiovascular disease than married participants.
Also, the single, divorced, and widowed participants had a 16 percent higher risk of coronary artery disease, as well as a 42 percent higher chance of dying from it. These participants were also 55 percent more likely to die from a stroke.
A more detailed analysis of the data revealed that going through a divorce heightened the risk of heart disease by 35 percent for both men and women, and being widowed increased chances of having a stroke by 16 percent.
Finally, never marrying raised the risk of dying after a heart attack by 42 percent. However, no statistical difference was noted in the case of survival after a stroke.
Strengths and limitations of the study
The authors note some strengths and limitations to their study. They claim that this is the largest study of its kind to date, and that having access to the participants' ethnicity and age makes the findings widely applicable.
However, the researchers admit that they had no information on same-sex civil partnerships or marriages, and that the quality of the marriage was not considered.
Also, it could be the case that simply living with someone, rather than being married to them, is what benefits heart health. Another weakness is that the studies examined varied greatly in the methods they used.
Finally, because the research is observational, it cannot draw any conclusions about the causal mechanisms behind the associations found.
The authors speculate on a few potential reasons why marriage might protect heart health.
These include improved financial security, overall higher well-being, stronger adherence to medication, and a prompter recognition of health problems and taking appropriate action.
Wong and colleagues conclude:
"Future research should focus around whether marital status is a surrogate marker for other adverse health behavior or cardiovascular risk profiles that underlies our reported findings or whether marital status should be considered as a risk factor by itself."