Researchers at the University of Southern California (USC) seem to have found the reason why women tend to live longer than men. According to them, women live longer because of a difference in vulnerability to heart diseases.

Until last century, there was no significant difference in the mortality rates of men and women. But as infection-prevention methods, dietary changes and other lifestyle factors began to emerge, the mortality rate of males started to decline in the early 1900s. However, women showed a gradual increase in longevity.

Researchers at USC's Davis School of Gerontology found that heart-related conditions and diseases were the reason behind the disparity. "We were surprised at how the divergence in mortality between men and women, which originated as early as 1870, was concentrated in the 50-to-70 age range and faded out sharply after age 80," lead researcher Eileen Crimmins said in a statement.

The researchers examined data for nearly 1,763 people born between 1800 and 1935 in 13 developed nations. They found that for people age 40 and above, and born after 1880, the mortality rate for women declined 70 percent faster than the male mortality rate.

Smoking was identified as one of the main reasons behind greater male mortality. However, it was linked to only 30 percent of the excess deaths among men between ages 50 and 70, who were born after 1890. They found that cardiovascular illness remained the main reason for excess deaths among the males.

The greater number of deaths among the middle-aged and early older aged men due to heart-related illness has raised questions in the minds of the researchers. They now want to see if the heart disease risks differ between men and women.