The relapsing form of neuromyelitis optica (NMO) primarily affects women. The female to male ratio is greater than 4:1. Another form of NMO, in which an individual only has a single, severe attack extending over a month or two, is most likely a distinct disease that affects men and women with equal frequency. The onset of NMO varies from childhood to adulthood with two peaks, one in childhood and the other in adults in their 40s.
According to Mayo Clinic neurologist Dean Wingerchuk, MD, the prevalence and incidence of NMO have not been firmly established. “It has a worldwide distribution, and reported risk factors include females and non-Caucasian racial background,” says Dr. Wingerchuk. “Population-based studies of clinically diagnosed NMO have indicated prevalence rates from 0.32-4.4 cases per 100,000 population. In aggregate, the data suggests that there are likely more than 4,000 people with NMO in the United States, and possibly more than 10,000.” This means government or national funding is not assigned to researching NMO because not enough people in the U.S. have been diagnosed with this disease.
More Answers from Multiple Sclerosis Foundation