Multiple Sclerosis Is Increasingly Becoming A Woman's Disease: Why?

"That's an increase in the ratio of women to men of nearly 50 percent per decade," said study author Gary Cutter, PhD, of the University of Alabama at Birmingham School of Public Health. "We don't yet know why more women are developing MS than men, and more research is needed."

Cutter said researchers will need to explore multiple changes that have occurred for women over the last several decades, including the use of oral contraceptives, earlier menstruation, obesity rates, changes in smoking rates, and later age of first births.

"We also need to ask the general questions about what women do differently than men, such as use of hair dye and use of cosmetics that may block vitamin D absorption," he said. "At this point we're just speculating on avenues of research that could be pursued."

Cutter said the largest increase in the ratio has been for those whose MS started at younger ages.

For the study, researchers examined a database (the North American Research Committee On Multiple Sclerosis, or NARCOMS, hosted at Barrow Neurological Institute in Phoenix, Ariz.) of 30,336 people with MS and determined the male/female ratio according to the year the disease was diagnosed and the age of the person when the disease started.

The study was supported by the Consortium of Multiple Sclerosis Centers.