Women who have multiple sclerosis are more likely to have a certain gene associated the disease than men with MS, says a study published in a recent online issue of Neurology, the medical journal of the American Academy of Neurology.

Research also 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 isn't known, but evidence suggests that it is triggered by environmental factors in people who are genetically susceptible to the disease.

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.

The study examined the HLA genes of more than 1,000 families in which more than one person has MS. Researchers studied the genes of about 7,100 people, which included just over 2,100 people with MS.

The researchers looked at the HLA genes 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.

The researchers found that women with MS were 1.4 times more likely to have the HLA gene variant associated with MS than men with MS. A total of 919 women and 302 men had the HLA gene variant, compared with 626 women and 280 men who didn't have the gene variant.

This fits with other research by the same research group showing that the environment interacts with this gene region to produce modification in risk associated with it.

"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," says study author Dr. George C. Ebers, of the University of Oxford in the United Kingdom and a member of the American Academy of Neurology.

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.

"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," says Dr. Orhun Kantarci, of the Mayo Clinic in Rochester, Minn., and a member of the American Academy of Neurology, who wrote an editorial on the study. "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.