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According to the Centers for Disease Control and Prevention (CDC), women on average live anywhere from 5 to 7 years longer than men. There are several key factors that influence the life expectancy differences between men and women. Men and boys are more likely to be involved in risky and violent behavior than women and girls. More men die from suicide, murder, car accidents, and cardiovascular related diseases than do women. The major factor however, that influences life expectancy is genetic make-up. Women typically live longer than men because of their genes.
Key Takeaways: Why Women Live Longer Than Men
- Women typically outlive men due to differences in genetic make-up.
- Male mitochondrial DNA mutations increase the rate at which males age. However, these same mutations in females do not influence aging.
- Dual X sex chromosomes provide protection for women against X chromosome gene mutations. These mutations are always expressed in males because they only have one X chromosome.
- The female hormone estrogen provides protection for women against cardiovascular related diseases.
- Immune system function declines more slowly in women than in men.
- Men are more likely than women to be involved in dangerous activities and take greater health risks than women.
Men Age Faster Than WomenMitochondria. GUNILLA ELAM/Getty Images
Scientists believe that the key to why women live longer than men is gene mutation. DNA mutations in the mitochondria of men account largely for the differences in life expectancy between men and women. Mitochondria are cell organelles that provide the energy needed for cellular function. With the exception of red blood cells, all cells have mitochondria. Mitochondria have their own DNA, ribosomes, and can make their own proteins.
Mutations in mitochondrial DNA were found to increase the rate at which males age, thus lowering their life expectancy. These same mutations in females however, do not influence aging. During sexual reproduction, the resultant offspring receive genes from both the father and mother. Mitochondrial DNA however, is only passed on via the mother. Mutations that occur in female mitochondria are monitored through genetic variation so that only favorable genes are passed from one generation to the next. Mutations that occur in male mitochondrial genes are not monitored so the mutations accumulate over time. This causes males to age faster than females.
Sex Chromosome DifferencesThis is a scanning electron micrograph (SEM) of human sex chromosomes X and Y (Pair 23). The X chromosome is much larger than the Y chromosome. Power and Syred/Science Photo Library/Getty Images
Gene mutations in sex chromosomes also influence life expectancy. Sex cells, produced by male and female gonads, contain either an X or a Y chromosome. The fact that females have two X sex chromosomes and males only have one must be taken into account when considering how sex chromosome mutations affect males and females differently. Sex-linked gene mutations that occur on the X chromosome will be expressed in males because they only have one X chromosome. These mutations often result in diseases that lead to premature death. Since females have two X chromosomes, a gene mutation on one X chromosome can be masked as a result of genetic dominance relationships between alleles. If one allele for a trait is abnormal, its paired allele on the other X chromosome will compensate for the abnormal chromosome and the disease will not be expressed.
Sex Hormone Differences
Another contributing factor to the differences in life span between men and women has to do with sex hormone production. Male and female gonads produce sex hormones needed for the growth and development of primary and secondary reproductive system organs and structures. The male steroid hormone testosterone raises levels of low-density lipoproteins (LDL) cholesterol, which promotes plaque buildup in arteries and increases the risk of heart disease and stroke. However, the female hormone estrogen lowers LDL levels and raises high-density lipoproteins (HDL) levels, thus reducing the risk of developing cardiovascular related diseases. Women tend to develop cardiovascular diseases later in life, typically after menopause. Since men tend to develop these diseases earlier in life, they die sooner from them than do women.
Men's Immune Systems Age Faster Than Women'sThis is a colored scanning electron micrograph (SEM) of T lymphocyte cells (smaller round cells) attached to a cancer cell. T lymphocytes are a type of white blood cell and one of the components of the body's immune system. Steve Gschmeissner/Science Photo Library/Getty Images
Changes in blood cell composition influence the aging process for both men and women. Women show a slower decline in immune system function than men, resulting in longer life expectancy. For both sexes, the number of white blood cells decrease with age. Younger men tend to have higher levels of lymphocytes than women of similar age, however these levels become similar as men and women get older. As men age, the rate of decline in specific lymphocytes (B cells, T cells, and natural killer cells) is faster than in women. An increase in the rate of decline in red blood cells is also seen in men as they age, but not in women.
Men Tend to Live More Dangerously Than WomenThis man is standing under a risky balancing boulder. Nick Dolding/The Image Bank/Getty Images
Men and boys tend to take huge risks and put themselves in harms way. Their aggressive and competitive nature leads them to engage in dangerous activities, often to get the attention of females. Men are more likely than women to be involved in fights and to act aggressively with weapons. Men are also less likely than women to engage in activities that promote safety, such as wearing seats belts or helmets. In addition, men are more likely than women to take greater health risks. More men smoke, take illegal drugs, and over indulge in alcohol than women. When men refrain from engaging in risky types of behaviors, their longevity increases. For example, married men take less risks with their health and live longer than single men.
Why do men take greater risks? An increase in testosterone levels at puberty is associated with thrill seeking and greater risk taking. In addition, the size of a region of the frontal lobes in the brain contributes to risky behavior. Our frontal lobes are involved in behavior control and inhibiting impulsive responses. A specific region of the frontal lobes called the orbitofrontal cortex manages this activity. Studies have found that boys with a larger orbitofrontal cortex take more risks in relation to high testosterone levels than do girls. In girls, a larger orbitofrontal cortex is linked to reduced risk taking.
- "It's in our genes: Why women outlive men." ScienceDaily. ScienceDaily, 2 August 2012, www.sciencedaily.com/releases/2012/08/120802122503.htm.
- Peper, Jiska S., et al. “Development of Risk Taking: Contributions from Adolescent Testosterone and the Orbito-Frontal Cortex.” Journal of Cognitive Neuroscience, 1 Dec. 2013, cognet.mit.edu/journal/10.1162/jocn_a_00445.
- "Women's immune systems remain younger for longer." ScienceDaily. ScienceDaily, 15 May 2013, www.sciencedaily.com/releases/2013/05/130514213056.htm.