Girls whose periods begin before the age of 13 are at higher risk of becoming adult women with diabetes, compared to girls who start menstruation later, new research shows.

An earlier onset of periods also appears to hike a woman's odds for stroke before the age of 65, the same study found.

Why the link? According to the research team at Tulane University in New Orleans, exposure to circulating estrogens may raise diabetes and heart risks, and women who start menstruation earlier in life are exposed for longer.

The findings were published Dec. 5 in the journal BMJ Nutrition Prevention & Health.

The research was led by Tulane epidemiologist Dr Sylvia Ley. Her team tracked nearly 20 years (1999-2018) of data on over 17,000 U.S. women. The women ranged in age from 20 to 65 at the beginning of the study.

All of the women gave information on when they began menstruating.

About 10% of the women in the study had a diagnosis of type 2 diabetes, while 11.5% had heart disease.

After accounting for weight, age, race and history of childbearing, among other factors, having a first period before the age of 13 was linked to higher odds for type 2 diabetes.

The risk rose higher the earlier that periods began: For example, a woman who began menstruating at age 10 or younger faced a 32% higher odds for diabetes, while a woman who started at age 12 faced a 29% higher risk, Ley's group reported.

Beginning menstruation at age 10 or younger was also tied to a doubling of the risk for stroke under the age of 65, the study found.

The study wasn't designed to prove cause-and-effect, the researchers stressed in a journal news release.