Recent research has found that more women than men have been diagnosed with multiple sclerosis over the past few decades. The study found that the two to one ratio of women to men with the disease in the United States in 1940 has grown to approximately four to one in 2000.

The results of the study will be presented at the American Academy of Neurology's 59th Annual Meeting in Boston, from April 28 to May 5.

Multiple Sclerosis is a chronic, inflammatory, demyelinating disease that affects the central nervous system. It can cause a variety of symptoms, including changes in sensation, visual problems, muscle weakness, depression, difficulties with coordination and speech, severe fatigue, cognitive impairment, problems with balance, overheating, and pain. MS will cause impaired mobility and disability in more severe cases.

According to reports in Asian News International, study author Gary Cutter, of the University of Alabama at Birmingham School of Public Health said, "That's an increase in the ratio of women to men of nearly 50 percent per decade."

"We don't yet know why more women are developing MS than men, and more research is needed," Cutter said adding that scientists should focus various factors such as the use of oral contraceptives, earlier menstruation, obesity rates, changes in smoking rates, and later age of first births.

The study data was gathered from a large database called the North American Research Committee on Multiple Sclerosis (NARCOMS), which includes information on almost 31,000 people with multiple sclerosis. Volunteers provided semi-annual demographic and clinical details about their disease.

About 400,000 people in the United States have multiple sclerosis, and worldwide, the disease affects about 2.5 million people, according to the society. The disorder is generally first diagnosed in people between the ages of 20 and 50.