MS diagnosis rate soaring for Canadian women

Dr. George Ebers of Oxford University
 
CTV.ca News Staff
 
 Oct. 30 2006:-  A new study has pinpointed an alarming trend that suggests women with multiple sclerosis now outnumber men in Canada by a ratio of more than three to one.

The researchers, led by Dr. George Ebers of Oxford University, examined Canadian data on multiple sclerosis sufferers. They also found that this gender ratio has been rising for at least 50 years.

More than 1,000 new cases of the disease will be diagnosed this year in Canada, and an estimated 55,000 to 75,000 people are currently living with the disease.

The Canadian research shows:

In 1931, for every one man diagnosed with MS, 1.8 women received the diagnosis.
Around 1940, the picture starts to change. The rate of MS cases in men stays relatively the same, but in women, it rises.
And by 1980, for every one man diagnosed, more than three women develop MS.
The team that conducted the research into the Canadian multiple sclerosis data is speculating that an unknown contributing factor has emerged in the last half century to make MS a female-dominated disease. The findings will appear in the November edition of the Lancet's neurology journal.

"Since there is no indication that multiple sclerosis in men has decreased, it seems that the sex ratio change is determined by a preferential increase in affected women," the study says.

Canada has among the highest rates in the world, as do many nations in northern Europe, prompting speculation genetics and geography may increase the risk for people who live in countries far from the equator.

There is growing acceptance of the theory that a vitamin D deficiency due to low sun exposure may be a contributing factor in the development of the often-disabling disease.

If there is a link between vitamin and multiple sclerosis, this could suggest it is a result of less time spent outdoors.

Other possible factors that could be contributing to the trend include the changing role of women in the work force, dietary habits, increase in smoking among women, use of oral contraceptives, and changes in the timing of childbearing years.

Given that the trend in the sex ratio of immigrant patients was similar to that of Canadian-born patients, the researchers believe that this trend is mirrored worldwide.

Previous research found that having an older brother or sister with MS does not protect younger siblings from developing the disease, suggesting that a genetic predisposition and other factors are likely behind the onset of multiple sclerosis.

This findings cast into doubt the theory that children whose immune systems are exposed to infections introduced by older siblings are less likely to develop the potentially debilitating disease.

The study found that babies concieved during the summers, when their mothers have higher levels of vitamin D in their blood are less likely to develop MS later in life.

"Some of the risk appears to be gestational, and very early in life," Dr. Ebers said.

This suggests MS may be preventable, if scientists can figure out what's going on, and if it's as simple as a woman having adequate levels of Vitamin D before or during pregnancy or early childhood.

Multiple sclerosis is an unpredictable disease caused by inflammation and patchy destruction of the protective myelin covering the central nervous system. Those with the progressive disease tend to go through sporadic periods of attack followed by recovery.

The cause of MS is not known, but most researchers believe it is an autoimmune disease, according to the Multiple Sclerosis Society of Canada. Age of onset among sufferers is usually between 20 and 40, but MS has also been diagnosed in children.

Multiple sclerosis initially may cause numbness and tingling in the extremities and temporary loss of vision in one eye. As the disease develops, sufferers may experience a range of symptoms, including extreme fatigue, balance and co-ordination problems, muscle stiffness and weakness, and speech and cognitive difficulties.

With files from CTV's medical correspondent Avis Favaro and medical producer Elizabeth St. Philip