We performed a prospective, study in North Canterbury, New Zealand from 1985-2006, to ascertain the incidence of amyotrophic lateral sclerosis (ALS) over that 22 year period, and to detect patterns of change in incidence that may provide aetiological clues to the cause of ALS. We also sought to identify factors that might influence survival in this large community-based cohort.
A prospective database of all patients seen at the Department of Neurology at Christchurch Public Hospital (CPH) formed the basis of this study. Additional cases were identified through hospital coding data and from neurologists’ private practice records. All patients were retrospectively classified using the El Escorial criteria through chart review, 244 cases of ALS were detected. Incidence rates increased on average 3% per year over the 22 years, from approximately one per 100 000 per year in the mid 1980s to nearly four per 100,000 per year over the last five years of the study. Older age, bulbar symptoms and male sex adversely affected survival. Less than 5% were alive 5 years after diagnosis; the median survival was 17.6 months after diagnosis. Contemporary supportive therapies did not extend survival.
We report the highest recorded incidence of ALS to date. The incidence of ALS in Canterbury increased over a 22 year period. We were unable to confirm improvement in survival using contemporary supportive therapies and confirmed older age, male sex and bulbar onset as adverse prognostic factors. The increasing incidence is not explained by ageing of the population.