Lead author Sarah Floud of the University of Oxford in England and colleagues analyzed data collected for a large British study of women's health.
The study involved 730,000 women who were an average age of 60. Over the nine-year study period approximately 30,000 developed and 2,000 died from heart disease.
The study, published in the journal BMC Medicine, found married women or those living with a partner had the same risk of developing heart disease as unmarried women -- including single, widowed and divorced women -- but the chance of dying from heart disease was 28 percent lower.
The researchers factored in age, socioeconomic status and lifestyle, but the lower risk of death from heart disease remained, the study said.
The researchers said the reasons for the findings were not known.
The study authors suggested one reason could be that the spouses of married women might encourage them to seek early medical treatment for symptoms, but there may be other explanations. Other studies indicated partners tended to encourage their spouses to take medication and make changes in unhealthy lifestyles, Floud said.