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, migration patterns, genetics and infectious processes.
According to the Atlas of MS, there are about 2.3 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.
Although MS is found in all parts of the world, its prevalence varies greatly, being highest in North America and Europe, and lowest in sub-Saharan Africa and East Asia. It is almost unheard of in certain populations such as the Inuits, New Zealand Maoris and Australian Aborigines.
MS affects at least twice as many more women than men, suggesting a role of hormones in the disease process.
Most people are diagnosed between the ages of 25 and 35, although around three to five per cent of people with MS are diagnosed as children, and it can occur in much older adults.