There is a wide range of age at initial symptom onset in amyotrophic lateral sclerosis despite a mean age of 65 years in population-based studies. 'Young-onset' amyotrophic lateral sclerosis typically refers to patients younger than ∼45 years and accounts for about 10% of cases in contemporary series. A review of published cases of amyotrophic lateral sclerosis from 1850 to 1950 revealed a far higher proportion of cases with young onset (>50%), with a steady decline to the contemporary figure. It is possible that this is not solely explained by increases in life expectancy. While there is still a rich variation in phenotypes among cases of young-onset amyotrophic lateral sclerosis, bulbar onset was found to be significantly under-represented in analysis of a large patient database, with implications for age-related vulnerabilities pertaining to focality of symptom onset. The timing of initiating pathological processes in relation to the emergence of symptoms is discussed, including the potential role of very early development and the interaction of epigenetic and environmental factors.
Amyotrophic lateral sclerosis (ALS, motor neuron disease) is a neurodegenerative disorder of motor neurons leading to paralysis and eventual death by respiratory failure. Median survival is 2-3 years. Susceptibility genes, environmental triggers and disease related prognostic factors have been established, but environmental effects on survival are yet to be investigated. We analysed survival in the South-East England ALS register (SEALS register). Kaplan-Meier and Cox regression analyses were used to investigate survival in London, coastal and rural areas according to postcode at diagnosis. Results showed that there were 933 cases of ALS identified in the catchment area during the study period (1994-January 2012). Cox regression demonstrated a highly significant model for survival with significant protective variables: coastal residency, riluzole use and younger age at onset. Significantly worse survival was associated with London residency, older age as well as definite and probable El Escorial classifications. In conclusion, these findings suggest the possibility of an environmental effect on survival in ALS.
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