8 surprising facts about women’s health and aging

Women live longer than men on average, but they spend 25% more time in worse health. It’s also no secret that women are still underrepresented in animal research and clinical research, despite gains since Congress passed the National Institutes of Health Revitalization Act of 1993, mandating the inclusion of women and people of color in NIH-funded research. (Even today, female animals are excluded from basic research because of the belief that cyclical fluctuations in their reproductive hormones introduce too much noise and variability to the outcomes.) Of the $45.2 billion NIH budget for 2022, only $4.6 billion was focused on women's health—and of that, only $116 million on female reproductive aging.

Even with the White House Initiative on Women’s Health Research, which launched in 2023, women’s health is woefully underfunded. According to Jennifer Garrison, Ph.D., assistant professor at the Buck Institute for Research on Aging, and co-founder and director of the Global Consortium for Reproductive Longevity and Equality, "women's health is often treated as a niche subcategory of medicine with paltry research funding, despite the fact that we are talking about half the global population. The lack of funding combined with an overreliance on male physiology from cell culture to animal models—up to and including humans—has left a gaping hole in our knowledge." 

Here are eight surprising facts about women’s health and aging, many of which science has yet to explain.

1. Older age at menopause correlates with increased longevity 

Figure: Life expectancy by age at menopause (years). Adapted from Ossewaarde, M.E., et al. Epidemiology. 2005;16(4):556-562.

The average age of menopause onset in the U.S. is 51, but can be as early as 40. It’s accompanied by lower levels of estrogen and progesterone—a change in hormone production that comes with an increased risk of adverse health outcomes. Studies demonstrate that women who undergo menopause later live longer. (One study showed that women who entered menopause after age 55 lived two years longer than those who entered menopause before age 40.) The age at menopause appears to be strongly influenced by genetics, in particular those genes involved in DNA repair.

2. Brothers of women who go through menopause later also live longer

Women who go through menopause later in life tend to live longer—and so do their brothers. Using two historical sources of data on sibships before the introduction of birth control, one study found that relative survival after age 50 was greater for men with a late-fertile sister. Why the survival advantage for brothers? The study suggests there are likely common genetic variants underlying both late menopause and longevity.

3. Women spend 25% more of their lives in poor health than men

The life expectancy of women globally is 73.8 years, compared with 68.4 years for men. Sounds rosy, but the reality is women spend 25% more of their lives in poor health and disability compared to men. Why the gap? A report by the World Economic Forum and the McKinsey Global Health Institute cites these four factors: research bias that favors male biology, poor data about women’s health, barriers to care, and lack of investment in women’s health conditions. 

4. Females are born with all the eggs they will ever have 

The female ovaries produce eggs and hormones—but they aren’t capable of making new eggs. A female fetus at 20 weeks of gestation contains six to seven million immature eggs (oocytes) in her developing ovaries. As women age, the number of eggs drastically declines. When a female baby is born, she has only one to two million oocytes, which further declines to about 300,000-400,000 by puberty. Only about 12% of eggs remain by age 30, and 3% by age 40. “The ovary is probably the only organ that loses its function prior to its first use,” according to Francesca Duncan, Ph.D., assistant professor of obstetrics and gynecology at Northwestern University Feinberg School of Medicine.

5. Ovaries age much faster than other tissues

The ovary is the first organ to age, and it happens roughly 2.5 times faster than the rest of the body. Ovarian aging contributes to infertility and a loss of endocrine function. Because of this rapid decline and the important role hormones play in our overall health, this means women experience an erratic decline in the health and function of their other organs, in contrast to men who experience a more gradual decline. In fact, research shows that hormonal changes associated with menopause accelerate biological aging in the rest of the body by 6%. Previously regarded as reproductive organs, the ovaries are now thought of as “architects of health in female bodies.”

6. Menopause has a profound negative effect on women's health

Menopause marks the point in time when a woman has not experienced a menstrual cycle for 12 months. Many people are familiar with some of the symptoms—hot flashes, sleep problems, mood changes—but the truth is that menopause has far-reaching effects on the female body. The culprit is ovarian aging and the associated decline in estrogen. According to research, estrogen deficiency impacts tissues and organs with estrogen receptors, including the ovary, endometrium, vaginal epithelium, skin, hypothalamus, and urinary tract. But it also has negative consequences for the cardiovascular, musculoskeletal, and immune systems, as well as emotional and sleep patterns, cognitive ability, and energy metabolism.

7. Hormone replacement therapy is misunderstood

Hormone replacement therapy (HRT) was a popular treatment in the 1990s. That changed in 2002 when the Women’s Health Initiative (WHI) published a widely publicized report claiming that HRT increased the risk of breast cancer and coronary disease in all women receiving the treatment. Despite being based on a narrow cohort of postmenopausal, asymptomatic women, the misinterpretation of the 2002 study had detrimental effects, depriving a generation of women of HRT. Subsequent studies from the WHI acknowledge HRT as the most effective treatment for managing menopausal vasomotor symptoms and clearly demonstrate protective effects of HRT for coronary disease and a reduction in mortality, particularly among women who initiate HRT within 10 years of their last menstrual period. These findings are consistent with the vast majority of the published literature.

8. Scientists don’t understand why humans experience menopause