TEMPO.CO, San Diego - Women with later menarche and later menopause are more likely to reach age 90 than those whose reproductive milestones come at earlier ages, suggests a new study.

"People have always wondered whether the timing of reproductive events affect longevity, but no study to date has evaluated that relationship," said lead author Aladdin Shadyab, of the University of California, San Diego School of Medicine.

The research team used data collected from 16,251 participants in the Women's Health Initiative, starting between 1993 and 1998 and continuing until August 2014.

All the women were born before September 1924; 8,892, or 55%, survived to age 90.

Women who were at least 12 years old at menarche were about 9% more likely to reach age 90 than those who were younger.

And women who were at least 50 when their periods stopped were about 20% more likely to reach age 90 than women who entered menopause before age 40. This was true whether menopause was natural or surgical.

A longer reproductive lifespan was also tied to longevity. Women who menstruated for more than 40 years were 13% more likely to reach age 90 than those who had less than 33 reproductive years, the authors reported in a paper released July 27 by the journal Menopause.

Shadyab and colleagues can't say why later periods and later menopause are tied to longer life, but the link could be related to lifedata-style factors and genetics.

"It is possible that those who begin menstruating later and those who experience menopause at older ages are in better health long term," Shadyab told Reuters Health.

There could also be genes that affect both the start of periods and menopause and a woman's length of life, he added.

"Further studies are needed to determine why reproductive factors predict living to age 90 in women," he said.

Dr. JoAnn Pinkerton of the University of Virginia in Charlottesville, who is executive director of The North American Menopause Society, agrees that lifedata-style factors and genetics are likely behind the link between later reproductive milestones and longevity.

Pinkerton, who was not involved in the study, said research suggests that hormones that may protect women's hearts are lost during menopause.

Also, she said some behaviors, such as smoking, have an impact on overall health and on the timing of menopause.

REUTERS