Marriage may protect against the development of heart disease/stroke as well as influencing who is more likely to die of it, suggests a pooled analysis of the available data, published online in the journal Heart.
The findings prompt the researchers to suggest that marital status should be included as a risk factor for heart disease/stroke and likely survival in its own right.
Most (80%) cardiovascular disease can be attributed to well known risk factors: age; sex; high blood pressure; high cholesterol; smoking; and diabetes. But it's not clear what influences the remaining 20 per cent.
The findings of previous research on the impact of marital status have been somewhat mixed, so in a bid to clarify the issues, the authors trawled research databases for relevant published studies.
They drew on 34 out of a total of 225, all of which had been published between 1963 and 2015, and involved more than 2 million people aged between 42 and 77 from Europe, Scandinavia, North America, the Middle East, and Asia.
Pooled analysis of the data revealed that, compared with people who were married, those who weren't (never married, divorced, widowed) were at heightened risk of developing cardiovascular disease (42%) and coronary artery heart disease (16%).
Not being married was also associated with a heightened risk of dying from both coronary heart disease (42%) and stroke (55%).
When the data were broken down further, the analysis showed that divorce was associated with a 35 per cent higher risk of developing heart disease for both men and women, while widowers of both sexes were 16 per cent more likely to have a stroke.
While there was no difference in the risk of death following a stroke between the married and the unmarried, this was not the case after a heart attack, the risk of which was significantly higher (42%) among those who had never married.
The authors caution that the methods used and adjustments made for potentially influential factors varied considerably across all the studies, which may have affected the results of their analysis.
Similarly, there was no information on same sex partnerships or the quality of marriage, and the potential role of living with someone, as opposed to being married to them, was not explored.
But this is the largest study to date, with the age and ethnicity of the participants strengthening the wider applicability of the findings, the authors point out.
And there are various theories as to why marriage may be protective. These include earlier recognition of, and response to, health problems; better adherence to medication; better financial security; enhanced wellbeing; and better friendship networks.
"Future research should focus around whether marital status is a surrogate marker for other adverse health behaviour or cardiovascular risk profiles that underlies our reported findings or whether marital status should be considered as a risk factor by itself," the authors conclude.