Multiple sclerosis: it epidemiological, genetic, and health care impact.

Epidemiol Community Health 1995;49:563-569 Multiple sclerosis (MS) is a disease of relatively low incidence in the United Kingdom. Because of its long clinical course, however, its prevalence is moderately high and it makes a considerable impact on individuals, families, and on the health and social services. The inclusion in this review of the epidemiology, genetics, and health care of MS is intended to stress the inter-relationship between these three aspects of the disorder. MS is a demyelinating disease of the central nervous system. As a chronic disease, it offers a number of challenges to the epidemiologist. Firstly, although there are specific diagnostic criteria (see below), making a definitive diagnosis of MS is frequently difficult. Secondly, at any one time an unknown number of people who have symptoms of MS and who will subsequently be labelled as having the disease have yet to be diagnosed. Thirdly, its aetiology and the factors which determine the course of the disease are largely unknown. Lastly, new investigative techniques (particularly nuclear magnetic resonance imaging (MRI)) have shown central nervous system (CNS) lesions, characteristic of those found in MS in people who are free from symptoms. MRI may have important implications for monitoring disease activity in individual patients.1 Prevalence and incidence Several studies of UK populations have provided data on the prevalence of MS.2-7 These, as examples of the range of prevalence estimates, are summarised in the table. They have used a variety of methods for case ascertainment and different classification criteria. They are also spread over a number of