Amyotrophic lateral sclerosis in Nordland county, Norway, 2000-2015: prevalence, incidence, and clinical features

Abstract

Objective: There are some indications of increasing incidence of amyotrophic lateral sclerosis (ALS). Awareness of cognitive impairment in ALS has increased in recent years. We describe the epidemiology and clinical features of ALS in a county in northern Norway over a period of 15 years.

Methods: All patients with motor neuron disease (MND) living in Nordland County in the period 2000-2015 were identified and the medical records were scrutinized. The average annual incidence was calculated for the whole period and for five-year periods. Prevalence point was 1 January 2015.

Results: We identified 74 cases with MND. The crude point prevalence was 4.1 per 100,000. The average annual incidence was 2.1 per 100,000 for the whole period, 2.0 in the period 2000-2004, 2.3 in 2005-2009, and 2.0 in 2010-2014. All except one of the 22 patients with other forms of MND developed ALS during the course of the disease. The mean survival time was 38 months, patients with bulbar symptoms at diagnosis had a mean survival time of 29 months and those with solely spinal symptoms had a mean survival time of 50 months. Seven patients were diagnosed with frontotemporal dementia (FTD).

Conclusion: The incidence was stable during the study period. Other forms of MND converts to clinical ALS given time. Survival time is almost two years shorter in patients with bulbar symptoms at the first examination, compared to those with solely symptoms from spinal muscles. FTD was found in 9% of the patients.