Marriage may help to protect people against developing heart disease or having a stroke, according to research.
Single, divorced, and widowed people are at a heightened risk of developing the health problems, a study involving universities in the UK, the US and Australia has found.
Experts believe the additional social and emotional support provided by a spouse could be a factor behind the results.
They further suggest that marital status should be included as a risk factor for heart disease and stroke.
The study, led by Keele University in collaboration with the Universities of Aberdeen, Arizona and Macquarie University, found that 80% of cases of cardiovascular disease can be attributed to well known risk factors: age; sex; high blood pressure; high cholesterol; smoking; and diabetes.
It is not, however, clear what influences the remaining 20%, researchers said.
Their work drew on 34 studies, published between 1963 and 2015, involving more than two million people around the world aged between 42 and 77.
Analysis of the data showed that, compared with people who were married, those who were divorced, widowed or had never married had a 42% higher risk of developing cardiovascular disease and a 16% higher risk of coronary artery heart disease.
Not being married was also associated with a heightened risk of dying from both coronary heart disease (42%) and stroke (55%), the teams said.
Further analysis showed that divorce was associated with a 35% higher risk of developing heart disease for both men and women, while widowers of both sexes were 16% 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.
Possible explanations for the findings include people within marriages having earlier recognition of health problems; better adherence to medication; better financial security; enhanced wellbeing and better friendship networks, experts said.
Lead researcher, Chun Wai Wong of Keele University, said: "Our analysis showed that compared to married individuals, being unmarried was associated with increased coronary heart disease and both cardiovascular heart disease and stroke mortality in the general population.
"Our findings suggest that marriage has a protective effect on cardiovascular diseases, however, this could be attributed to the additional social and emotional support provided by having a spouse."
University of Aberdeen contributor Professor Phyo Kyaw Myint said: "There are several possible mechanisms that may explain why people who are married had reduced risk of heart disease.
"They may adopt balanced diet and lifestyle for example, through encouraging their partner to lose weight, do more physical activities or simply encouragement to go and see a doctor for seemingly minor ailments such as heartburn which can be due to heart disease."
There was no information on same sex partnerships, or on the quality of the marriages, and the potential role of living with someone, as opposed to being married to them, was not explored.
The study, also in collaboration with University Hospitals of North Midlands NHS Trust (UHNM) and the King Fahd Armed Forces Hospital, is published in the journal Heart.
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