Incidence and prevalence of motor neuron disease in two Danish counties

A total of 186 cases of motor neuron disease (MND) was identified in two Danish counties during the period 1974-1986. The average annual incidence rate was 1.4/100,000 population, and the male:female ratio of incidence rates was 1.5. Mean age at diagnosis was 64.3 +/- 10.0 years. The incidence rates increased significantly with advancing age and reached a maximum at age 60-79 years, followed by a nonsignificant decrease. The average point prevalence was 3.1/100,000 population. Bulbar symptoms were part of the initial symptoms in 65% of cases, and patients with bulbar onset were older than patients with spinal onset. Age- and sex-specific incidence rates indicated a marked male preponderance amongst the youngest patients, in contrast to a female preponderance in patients above 60 years with bulbar onset of MND. Familial MND accounted for 2.7% of cases.