Multiple sclerosis in Northern Ireland. A study of the date and place of birth of patients.

1,418 multiple sclerosis cases, 1,238 of whom were born in Northern Ireland, were analysed. A detailed study was made of the 783 cases born in Northern Ireland from 1901 to 1925. These cases were studied in relation to all live births that occurred in the administrative areas of the province during the period. The results showed a constant *case-rate over the years studied, and a remarkable deficiency of cases born in the city of Belfast. It was concluded that the risk of developing multiple sclerosis is not independent of the place of birth, but is independent of the year of birth of patients.