Characteristics of patients and controls in the questionnaire study population
| Amyotrophic lateral sclerosis (n=334) | Controls (n=538) | |
| Median age*, years (range) | 60 (24 to 82) | 59 (29 to 89) |
| Female, n (%) | 145 (43) | 246 (46) |
| Site at onset, n (%) | ||
| Bulbar | 86 (27) | |
| Spinal | ||
| Cervical | 114 (36) | |
| Thoracal | 4 (1) | |
| Lumbosacral | 102 (32) | |
| Multiple regions | 13 (4) | |
↵* Age at onset was used in the multivariate analysis.
All patients fulfilled the El Escorial criteria for probable and definite amyotrophic lateral sclerosis.