This is despite the fact that marriage makes no difference to women's chances of developing heart disease in the first place, researchers said.
The reasons for this difference are not known, but Dr Sarah Floud and colleagues at Oxford University's Cancer Epidemiology Unit suggest one explanation could be that the partners of married women may encourage them to seek early medical treatment for symptoms.
The researchers say there may be other possible explanations too.
For example, other studies have shown that partners tend to encourage their spouses to take medication and make changes in unhealthy lifestyles.
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Researchers found that married women, or those living with a partner, had the same risk of developing heart disease as unmarried women (this included single, widowed and divorced women). But the chance of dying from heart disease was 28 per cent lower.
The study took many factors into account that could have influenced the results, such as age, socio-economic status and lifestyle, but the lower risk of death from heart disease remained.
"This means that, over 30 years, about three in 100 married women would die from heart disease compared with about four in 100 women who are not married or living with a partner," said Floud.