Multiple sclerosis is a disease caused by damage to the nerve fibres in the central nervous system, which disrupts the signals sent to and from the brain. Multiple sclerosis is a progressive disease that worsens over time and eventually leads to death.
Multiple sclerosis is an autoimmune disease, a disease where the body’s immune system attacks healthy tissue within the body. In the case of multiple sclerosis, the immune system mistakes the protective covering that surrounds nerve fibres for a foreign body and mounts an immune response against it.
This substance that surrounds and insulates the nerves is called myelin and diseases that involve damage to this myelin are called demyelinating diseases. Destruction of the myelin disrupts the ability of the nerve to conduct signals, which may be slowed or stopped altogether.
Some experts believe a certain combination of genes may predispose to multiple sclerosis, while other theories suggest that viral infection of the immune and/or nervous system may be responsible. Research into the incidence of the condition across the globe has shown that multiple sclerosis is more common in countries that lie further north of the equator such as the UK and Scandinavia that in countries such as Malaysia or Ecuador, for example. One theory that supports this is that a lack of sunlight and subsequently vitamin D plays a role in the development of multiple sclerosis.
Worldwide, the median estimated prevalence of multiple sclerosis is 30 per 100,000 population. Globally, the median incidence of new cases annually is 2.5 per 100,000 population. Among different regions, the median estimated prevalence is highest in Europe, at 80 per 100,000 population. This is followed by a prevalence per 100,000 of 14.9 in Eastern Mediterranean regions, 8.3 in the Americas, 5.0 in the Western Paciﬁc, 2.8 in South East Asia and 0.3 in Africa.
The highest estimated prevalence of multiple sclerosis by country is found in Hungary at 176 per 100,000 population, followed by a prevalence per 100,000 of 150 in Slovenia; 149 in Germany; 135 in the United States; 133 in Canada; 130 in Czech Republic; 125 in Norway; 122 in Denmark; 120 in Poland; and 110 in Cyprus.
Studies have also shown that when countries are stratified by income, the median estimated prevalence of multiple sclerosis is greatest in the high income countries, at 89 per 100,000 population. This is followed by an estimated prevalence of 32 per 100,000 in upper middle income countries; 10 per 100,000 in lower middle income countries; and 0.5 per 100,000 in low income countries. The disease is more common among white populations than in non-white populations.
Reviewed by Sally Robertson, BSc