Prognostic factors in amyotrophic lateral sclerosis

Survival in patients with amyotrophic lateral sclerosis is highly variable. In a prospective study of 71 patients, we analyzed the influence of several clinical factors on survival: age of onset, sex, initial involvement (bulbar, upper extremities or lower extremities) and familial history. Mean time of evolution was 2.6 years, with 25% survival 5 years after onset. Patients under 45 years old had better survival than those over 45 (5.8 and 2.2 years, respectively, p < 0.002). The prognosis for women was worse (2.07 and 3.6 years for women and men, respectively, p < 0.001), probably because age of onset was later in women (61 versus 53 years, respectively, p < 0.006). Neither first symptom or familial history of the disease affected prognosis. We conclude that age at onset is a decisive prognostic factor that is inversely related to survival. In the design of clinical trials in which survival is a variable, the treatment and control groups should be matched for age.