Epidemiology is essentially the study of disease in people. It looks at the patterns, causes and effects of health and disease conditions in defined populations. Epidemiological studies have helped to identify factors that may be related to the risk of developing MS, such as latitude, migrations patterns, genetics and infectious processes.
According to the Atlas of MS, there are about 2.1 million people in the world with MS, although the number may be much higher as it is likely that many people with MS remain undiagnosed in certain parts of the world. It is found in all parts of the world, including Asia and Africa, although it is more common among Caucasians, particularly people of Northern European descent. Despite being widespread, it is almost unheard of in certain populations such as the Inuits, New Zealand Maoris and Australian Aborigines.
It affects more women than men by at least 2-3 times, suggesting a role of hormones in the disease process. Most people are diagnosed between the ages of 25-35, although around 3-5% of people with MS are diagnosed as children and it can also occur in significantly older adults.