Research has shown that the number of people diagnosed with MS has been rising, and the rate has been rising faster for women than for men.

The cause of MS is not known, but evidence suggests that it is triggered by environmental factors in people who are genetically susceptible to the disease. It appears the environment interacts with this gene region to produce modification in risk associated with it. This is an epigenetic mechanism. Epigenetic transformation refers to those processes which cause normal cells to become tumor cells without the occurrence of any mutations.

George C. Ebers, MD, FMedSCi, of the University of Oxford in the United Kingdom and a member of the American Academy of Neurology states:

“Our findings also show women with the HLA gene variant are more likely to transmit the gene variant to other women in their families than to men.”

MS is known to occur more frequently in areas that are farther from the equator. Epidemiologists look at many factors including variations in geography, demographics, genetics, infectious causes, and migration patterns, in an effort to understand why. Studies of migration patterns have shown that people born in an area of the world with a high risk of MS, who then move to an area with a lower risk before the age of 15, acquire the risk of their new area. Such data suggest that exposure to some environmental agent that occurs before puberty may predispose a person to develop MS later on.

Some scientists think the reason may have something to do with vitamin D, which the human body produces naturally when the skin is exposed to sunlight. People who live closer to the equator are exposed to greater amounts of sunlight year-round. As a result, they tend to have higher levels of naturally-produced vitamin D, which is thought to have a beneficial impact on immune function and may help protect against autoimmune diseases like MS. The possible relationship between MS and sunlight exposure is currently being looked at in a Society-funded epidemiological study in Australia.

The main gene associated with MS is the human leukocyte antigen (HLA) class II gene, but most of the risk comes from interaction of both parental genes.

Researchers at the University of Oxford in the United Kingdom found that women with MS were 1.4 times more likely to have the HLA gene variant associated with MS than men. The genes of 7,093 people were tested, including 2,127 people with MS. A total of 919 women and 302 men had the HLA gene variant, compared to 626 women and 280 men who did not have the gene variant.

The study published online issue of Neurology, also examined the HLA genes of 1,055 families with more than one person with MS in the family. The researchers looked at what the HLA genes were for the people with and without MS, whether people with MS inherited the susceptibility gene from their mother or their father, and what the relationship was between people in the same family with MS. The researchers also determined that second-degree relatives such as aunts and their nieces or nephews were more likely to inherit the gene variant than first-degree relatives such as siblings or parents and children.

Orhun Kantarci, MD, of the Mayo Clinic in Rochester, Minn., and also a member of the American Academy of Neurology added:

“It appears that the less the genetic sharing between individuals, the higher the interaction is between female sex and inheritance of the HLA gene variant. These findings pave the way for future studies of these genes, hopefully to advance our understanding of inheritance of complex diseases such as MS.”

The study was supported by the Multiple Sclerosis Society of Canada and the Multiple Sclerosis Society of the United Kingdom.

The American Academy of Neurology, an association of more than 22,500 neurologists and neuroscience professionals, is dedicated to promoting the highest quality patient-centered neurologic care. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as Alzheimer’s disease, stroke, migraine, multiple sclerosis, brain injury, Parkinson’s disease and epilepsy. For more information about the American Academy of Neurology, visit http://www.aan.com.

Written by Sy Kraft, B.A.