Background A small proportion of patients with amyotrophic lateral sclerosis (ALS) survive more than 5 years. The frequency of 5-year or longer survival with ALS in a USA population is unknown but may provide a baseline for studies that employ survival as a primary endpoint of analysis.

Methods All persons diagnosed as having ALS in Olmsted County between 1925 and 2004 were studied for demographic and clinical features. Longer-term survivors were defined as patients who lived 5 years or longer, tracheostomy-free, following symptomatic onset.

Results 94 patients (mean survival from symptomatic onset 2.95 years (95% CI 2.54 to 3.35), mean survival from diagnosis 1.89 years (95% CI 1.54 to 2.24)) were diagnosed as having ALS. Five-year or longer survivors accounted for 14% of the population of patients (95% CI 7.9% to 22.8%). The frequency of 5 year or longer survivors did not change over time. The mean survival of these individuals was 7.04 years (95% CI 6.14 to 7.94 years; range 5.11–9.35 years). They had a significantly longer mean time to diagnosis (1.77 years, 95% CI 0.95 to 2.58 years) as compared with survivors of less than 5 years (0.94 years, 95% CI 0.75 to 1.13 years) (p=0.02) but could not be reliably identified at the time of diagnosis by age, sex, clinical presentation or El Escorial category.

Conclusion Patients surviving more than 5 years following the symptomatic onset of ALS account for 14% of the total ALS population. This frequency has not changed over time. Patients with a survival of 5 years or longer are clinically similar to the total population ALS population in terms of age, gender, presentation and site of onset but have a longer time from symptomatic onset to diagnosis.

Grant number NIH AR30582.