Doctors may be able to predict as early as a woman's late 30s the age at which she will eventually experience menopause, based on how quickly the levels of one hormone in her blood change, according to a new study.

Researchers studied 293 women in their 30s and 40s, taking blood samples over several years to measure their levels of anti-mullerian hormone, or AMH, which is produced by the ovaries. They found that the amount of year-to-year change in AMH levels provided a good predictor of when the women experienced menopause.

Currently, the only way to estimate when a woman will enter menopause is by using her age — the average age that menopause occurs is 51, but women can also experience the change in their 40s or late 50s, according to the National Institutes of Health.

The new study showed that AMH levels explained nearly 82 percent of the variability between women.

Additionally, the researchers found that the women whose AMH levels changed the most reached menopause two years earlier on average, compared with women whose levels changed the least.

“AMH levels have added another indicator,” of the age menopause will begin, said study author Ellen Freeman, a research professor at the University of Pennsylvania. This is helpful because age “is not a wonderfully accurate predictor, it's just an available predictor,” she said.

The women in the study underwent blood tests every nine months for five years, and researchers followed them for up to 14 years later to see when they actually entered menopause.

It was known that AMH levels decrease as women age and approach menopause. The researchers found that combining a woman's age, hormone levels and the extent to which hormone levels were changing provided the most accurate indicator of the age at which she'd begin menopause.

Predicting how far a woman is from entering menopause could be useful to women with fertility problems, and those facing an increased risk of other health issues that may be affected by menopause, such as osteoporosis or heart disease, Freeman said.

But, she noted, the test is intensive, requiring patients to submit to repeated blood tests over a 3- to 5- year span, which may be difficult. Furthermore, while the study showed that the blood test predicted the menopause age for groups of women, it may be less accurate for any one individual, she said.

The test is not likely to work in women younger than their mid-30s, because AMH levels don't start declining until women are at least that age, Freeman said. “In our sample, the youngest women were 35.”

Kathleen Hill-Besinque, a women's health researcher and associate pharmacy professor at the University of Southern California, said the results were scientifically interesting, but added that she wasn't sure when this test might become useful in a clinical setting.

Additionally, the study researchers didn't compare their method of calculating menopause age to calculations based on the ages a woman's mother or sisters experienced menopause, Hill-Besinque said. The age of menopause is believed to have a genetic component.

However, Besinque said that the test could be used to help women with other health problems, or even further down the line, to encourage women to become healthier to delay menopause. For example, women who smoke tend to go through menopause sooner, and showing them how the habit affects their age of menopause could have “a tangible impact on their health,” she said.

The study was published online Aug. 24 in the journal Fertility and Sterility.

Pass it on: A blood test may be able to predict when a woman will go through menopause.

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