Smaller families may be one reason why women now outlive men, a new study suggests.
Researchers analyzed data from 140,600 people in Utah and found that men who were born in the early to mid-1800s lived an average of two years longer than women born at the same time.
This difference gradually reversed, and women born in the early 1900s lived an average of four years longer than men, the findings showed.
At the same time, the number of children per woman fell from an average of over eight in the early 1800s to just over four in the early 1900s. In addition, the investigators found that women who had 15 children or more lived an average of six years less than those with only one child.
There was no association between the number of children fathered by men and their life span, according to the study published recently in the journal Scientific Reports.
The findings suggest that lower birth rates need to be considered when trying to determine why women tend to live longer than men, the study authors concluded.
The results highlight “the importance of considering biological factors when elucidating the causes of shifting mortality [death] patterns in human populations,” said study leader Elisabeth Bolund. She is a postdoctoral research fellow in the department of ecology and genetics at Uppsala University in Sweden.
“Our results have implications for demographic forecasts, because fertility patterns and expected life spans are continuously changing throughout the world,” Bolund explained in a university news release.
“For example, the results suggest that as more and more countries throughout the world go through the demographic transition, the overall sex differences in life span may increase,” Bolund concluded.
The U.S. Centers for Disease Control and Prevention has more on life expectancy.