Though the difference in life expectancy between males and females has narrowed over the decades, the latter still lives longer on average. While lifestyle factors certainly play a role, a new review also shed light on an important biological difference.

According to the latest figures, life expectancy for women in the United States was found to be 4.9 years higher than that of men. The World Health Organization noted similar trends in other countries as well.

But the exact reasons behind this gender gap, which has survived numerous shifts throughout history, have remained unclear. There are, of course, external factors like the higher likelihood of risky behaviors among men. These would include smoking, alcohol consumption, working in relatively dangerous conditions, etc.

And apart from the genetic advantage, hormones can also influence longevity, as noted by Bertrand Desjardins, a researcher in the demography department of the University of Montreal.

"Estrogen, for example, facilitates the elimination of bad cholesterol and thus may offer some protection against heart disease," he wrote, adding that testosterone, on the other hand, is linked to violence and risk-taking.

In a new review, researchers are also exploring the role played by telomeres i.e. the caps at the end of each strand of DNA that protect our chromosomes. It is known that telomere length could help in predicting disease risk and how long a person will live.

Dr. Elissa Epel from the University of California in San Francisco will be presenting the review at the upcoming annual meeting of the North American Menopause Society (NAMS). She will deliver a Keynote Address entitled "Healthy Longevity and Telomeres: What Does Sex Have to Do With It?" at the San Diego event on Oct. 4.

Longer telomeres are associated with a lower risk of cardiovascular disease and even longer life for both sexes in some cases.

"Some experimental studies suggest estrogen exposure increases the activity of telomerase, the enzyme that can protect and elongate telomeres," Dr. Epel stated.

Studies published in recent times have taken to examining the factors which influence the length of telomeres and, in turn, what measures we can take to protect them and prevent shortening.

Among biological differences between the sexes, it is noted women have longer telomeres from birth. But this isn't necessarily permanent, she added, given that telomeres can be shortened prematurely due to stress or difficult childhood experiences that take a psychological toll.

In her address, Dr. Epel will include a special emphasis on female reproductive health, hormones, mental health and other such factors that could influence telomere length.

"We look forward to what promises to be a fascinating presentation with implications for slowing telomere attrition and age-related conditions," said Dr. JoAnn Pinkerton, who is the NAMS executive director.