Sci. Aging Knowl. Environ., 18 May 2005
March babies hit menopause earliest
R. John Davenporthttp://sageke.sciencemag.org/cgi/content/full/2005/20/nf37
Girls who are born as the days warm confront hot flashes sooner, according to new work. Women with March birthdays experience menopause nearly a year and a half earlier than those born in October. The findings add to the idea that the fetal environment can alter health in later life, although researchers aren't sure what triggers the difference in menopause timing.
Twenty years ago, medical scientist David Barker of the University of Southampton, U.K., formulated the "fetal origins of disease" hypothesis, after observing that small babies were especially likely to acquire heart problems as adults (see "From Womb to Tomb" and "From Womb the Bell Tolls"). Researchers have uncovered other in utero conditions that influence later years. For instance, babies born in the fall tend to live longer than those born in the spring. In addition, birth month appears to alter reproductive capacity: Women born in the summer tend to have fewer children than those born at other times of the year. In the new work, reproductive biologist Angelo Cagnacci of the Policlinico di Modena in Italy and colleagues investigated whether birth month influences the onset of menopause.
The researchers studied patient records for nearly 3000 women who sought medical care for menopause at four Italian hospitals over a 4-year period. The age at which women reached menopause varied in a wave pattern over the seasons. Age at menopause was lowest for women born in March--48.9 years--rose through the summer, peaked in October at 50.3 years, and dropped through the winter. Then the scientists analyzed the data for individuals who reached menopause early (at 40 years of age or earlier) or late (55 years of age or later). Women with early menopause were equally likely to have been born at any time of the year, whereas women with late menopause were more often born in the fall. Cagnacci isn't sure why, but he says that colder weather, shorter days, more infections, or changes in diet might mean that mothers gestating over the winter bear less robust babies.
"It's another indication that seasonal differences during early development can have effects late in your life," says behavioral biologist Susanne Huber of the Research Institute of Wildlife Ecology in Vienna, Austria. "Lots of environmental factors" could influence age of menopause, she says, but "we don't actually know which is the most important." The study selected for women who visited hospitals, Huber notes, so the subjects "might not be the healthiest." Future work should verify the results on a more random population. Demographer Gabriele Doblhammer-Reiter of the Max Planck Institute for Demographic Research in Rostock, Germany, says that the discovery meshes with her findings that women born during the fall live longer. Later menopause might reflect slower aging, she says, which would also increase life expectancy. Further work should clarify how the season of a woman's birth lays the foundation for how she weathers her golden years.
May 18, 2005
Science of Aging Knowledge Environment. ISSN 1539-6150