Multiple sclerosis in south Cambridgeshire: incidence and prevalence based on a district register.
STUDY OBJECTIVE: To establish an updated prevalence and incidence figure for multiple sclerosis on 1 July 1993, to determine the fate of the 374 patients prevalent in 1990, and to establish the origin of incident patients. DESIGN: Case ascertainment was from several sources including departmental records, local branches of the Multiple Sclerosis Society, general practitioners, nursing homes, and residential facilities for the disabled. Data collection was by personal interview using a standardised questionnaire and by retrospective analysis of departmental case notes. A prospective incidence register of newly diagnosed patents was maintained from 1990. SETTING: The Cambridge Health District of East Anglia covering 340,910 hectares in area and a population of 290,700. PATIENTS: Altogether 441 patients prevalent on 1 July 1993 were identified, of whom 328 were contacted so that clinical data could be collected. Seventy patients (16%) either declined to take part or access was denied by their general practitioner; 8 (2%) had died; and 35 (8%) were too ill or failed to respond to several requests for contact. MAIN RESULTS: A comprehensive re-evaluation of the south Cambridgeshire multiple sclerosis register revealed a prevalence of 441/290,700 population (152/10(5)) for all disease classifications on 1 July 1993. This represented an increase of 18% from 1990 and was a result of 138 additions and 71 deletions from the original list of 374 patients. The sex ratio of prevalent patients was 2.6 F:M, the mean age at disease onset was 31.7 years, and the mean age was 49 years. Mortality for 1990-93 was 3.3/10(5)/year and prospective maintenance of an incidence register recorded 96 new diagnoses for all classifications of multiple sclerosis over the five year period 1990-94 (6.6/10(5)/year). CONCLUSIONS: The increase in prevalence mainly resulted from improved case ascertainment identifying a further 58 patients who had been prevalent in 1990. Comparisons with other serial studies within the United Kingdom show similarities in proportional increase with successive studies indicating that serial survey may in part account for the observed latitudinal gradient within the United Kingdom. However, the observed prevalence (152/10(5)) in this second survey still falls short of the figure estimated from incidence and mortality data (186/10(5)).