Incidence and prevalence of ALS in Ireland, 1995-1997 - A population-basedstudy

Background: We conducted a prospective, population-based study of ALS in th e Republic of Ireland for the 3-year period 1995 to 1997. Methods: To ensur e complete case ascertainment, multiple sources of information were used, i ncluding consultant neurologists, neurophysiologists, primary care physicia ns, and the Irish Motor Neuron Disease Association. The El Escorial diagnos tic criteria for ALS were applied to all cases enrolled on the register and each patient was regularly followed up during his or her illness. Results: Between January 1, 1995, and December 31, 1997, 231 patients were diagnose d with possible, probable, or definite ALS, including 133 men (57.6%) and 9 8 women (42.4%). The average annual incidence rate was 2.1 per 100,000 pers on-years (95% CI, 1.8 to 2.4), and 2.8 per 100,000 person-years for the pop ulation older than 15 years (95% CI, 2.4 to 3.1). The incidence rate was hi gher for men, being 2.5 per 100,000 person-years (95% CI, 2.0 to 2.9), than for women, at 1.8 per 100,000 person-years (95% CI, 1.5 to 2.2), and incre ased with age for both sexes. The median age at onset was 64.2 years for me n and 67.8 years for women. On December 31, 1996, the crude prevalence was 4.7 per 100,000 of the total population (95% CI, 4.0 to 5.5), and 6.2 per 1 00,000 for the population older than 15 years (95% CI, 5.3 to 7.1). Adjusti ng to the 1996 Irish population as standard, the incidence of ALS in Irelan d during the 3-year study period is the third highest reported to date. Con clusions: There was a trend toward a higher incidence of ALS in the northwe stern region of Ireland, although the numbers of cases involved were small and further study is required.