As long as records have been kept, women have lived longer than men in almost every country. In industrialized countries, women live five to ten years longer than men. Nearly 85% of people over 100 years old are women. The reasons for this difference are undoubtedly related to a large number of sociological and biologic differences. This week, in an early online edition of the journal Gender Medicine, researchers reviewed current scientific knowledge on this gender gap.
Several biological reasons for men dying before women exist. Importantly, men have quicker telomere attrition or unwinding of their DNA, higher cortisol or stress hormone levels and a greater degree of cellular damage with stress. Women have heart attacks and strokes later in life than men possibly due to differences in hormone levels (estrogen and testosterone) earlier in life. The fact that women have two X chromosomes while men only have one X chromosome also may provide a survival advantage. If harmful genetic information is present on the single male X chromosome it is generally expressed in men. However, damage to one of two female X chromosomes may be hidden by the expression of that gene from the normal X chromosome. Mitrochondria (the energy producers within cells) are normally exclusively inherited or passed down from a mother as mitochondria from sperm is destroyed after an egg is fertilized. Because of this inheritance pattern, mutations in mitochondria tend to be weeded out if they harm females but are retained if they harm males.
Sociologic reasons for men dying earlier include more trauma, more physical activity, more risk taking, and the relative different roles men and women take in many societies. Men also tend to smoke more and eat more poorly than women – factors that have only come into play in recent centuries.
The authors point out that it is difficult to weigh the relative importance for each difference between a man and woman’s life expectancy. They concluded that further research into these differences may help develop strategies for healthy aging on both men and women.