Baseline characteristics for the study population
| No | Male/female (no) (%) | Age (years) at onset (range) | Spinal/bulbar (no) (%) | Mutations (no) | Mutation frequency (%) | |
| Sporadic amyotrophic lateral sclerosis | 451 | 265/186 (59/41) | 59 (20 to 84) | 349/102 (77/23) | 2 | 0.44 |
| Familial disposition for amyotrophic lateral sclerosis | 55 | 29/26 (52/48) | 57 (24 to 80) | 51/4 (93/7) | 1 | 1.82 |
Survival is defined as the interval between age at onset and age of death or tracheostomy shown in months, with the range shown in parentheses.