MS Increasingly a Woman's Disease
Steady Rise in Rates of Multiple Sclerosis Seen in Women
April 26, 2007 -- Women with multiple sclerosis (MS) now appear to outnumber
men with the disease by a ratio of four to one in the U.S., new research
The review of data from a voluntary MS registry suggests a steady increase
in MS rates among women over time, while rates among men appear to have
In 1940, twice as many women as men in the U.S. had multiple sclerosis. By
2000, four out of five cases were occurring among women, University of Alabama
professor of biostatistics Gary Cutter, PhD, tells WebMD.
That represents an increase in the ratio of women to men of nearly 50% per
decade, and it mirrors recent findings from other countries with more
comprehensive MS registries, including Canada, Norway, and Denmark.
It is not clear why MS rates seem to be increasing only among women, but the
observation could help researchers searching for the cause or causes of the
disease, Cutter says.
Some believe that environmental or viral influences early in life trigger
the disease in people who are genetically predisposed toward getting it. Though
there are many theories about what these triggers are, there is no proof that
any of them cause MS.
MS is a disease that affects the brain and spinal cord. Experts believe that
it is due to an abnormal response of the immune system attacking the myelin
sheath that surrounds nerve fibers. Myelin is needed for sending nerve signals
such as those that control movement. The National Multiple Sclerosis Society
estimates that 400,000 Americans have MS.
Searching for Clues
"We have to ask ourselves, 'What has been going on over the last 50
years or so that would affect women more than men?'" Cutter says.
During that time, obesity and smoking rates have increased among women, the
oral contraceptive was introduced, and there has been a trend toward earlier
menstruation and later childbirth.
These factors influence levels of the sex hormones, and there is some
evidence that sex hormones play a role in MS by suppressing the immune
Most women with MS have fewer symptoms of the disease during pregnancy.
After delivery, symptoms often return.
The sex hormone connection is just one avenue that needs to be explored,
He is scheduled to present findings from the study at next week's 59th
Annual Meeting of the American Academy of Neurology in Boston.
Probably No Single Cause
"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 says in a news release. "At this point
we are just speculating on avenues of research that could be pursued."
MS rates are highest among people living farthest from the equator, leading
to speculation that vitamin D deficiency due to low sun exposure contributes to
MS researcher and clinician Gary Birnbaum, MD, tells WebMD that there
probably isn't any single "smoking gun" that can explain all cases of
Birnbaum directs the Multiple Sclerosis Treatment and Research Center at the
Minneapolis Clinic of Neurology in Golden Valley, Minn. He is also a clinical
professor of neurology at the University of Minnesota School of Medicine.
"If it were that simple we probably would have been able to figure it
out by now," he says. "MS may not be a single disease. It may be a
syndrome. The pathway may actually be very different for different