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Research paper
The syndrome of cognitive impairment in amyotrophic lateral sclerosis: a population-based study
  1. Julie Phukan1,
  2. Marwa Elamin1,
  3. Peter Bede1,
  4. Norah Jordan2,
  5. Laura Gallagher2,
  6. Susan Byrne1,
  7. Catherine Lynch1,
  8. Niall Pender2,
  9. Orla Hardiman1,3
  1. 1Trinity College Institute of Neuroscience, Dublin, Ireland
  2. 2Department of Neuropsychology, Beaumont Hospital, Dublin, Ireland
  3. 3Department of Neurology, Beaumont Hospital Dublin, Dublin, Ireland
  1. Correspondence to Dr Marwa Elamin, Trinity College Institute of Neuroscience, Dublin, Ireland; marwaelamin08{at}


Background Despite considerable interest, the population-based frequency, clinical characteristics and natural history of cognitive impairment in amyotrophic lateral sclerosis (ALS) are not known.

Methodology The authors undertook a prospective population-based study of cognitive function in 160 incident Irish ALS patients and 110 matched controls. Home-based visits were conducted to collect demographic and neuropsychological data. Patients were classified using the recently published consensus criteria and by a domain-based classification of both executive and non-executive cognitive processes.

Results 13.8% of patients fulfilled the Neary criteria for frontotemporal dementia. In addition, 34.1% of ALS patients without evidence of dementia fulfilled the recently published consensus criteria for cognitive impairment. Non-demented ALS patients had a significantly higher frequency of impairment in language and memory domains compared to healthy controls. These deficits occurred primarily in patients with executive dysfunction. 14% of ALS patients had evidence of cognitive impairment without executive dysfunction, and no cognitive abnormality was detected in almost half the cohort (46.9%).

Conclusion Co-morbid dementia occurs in approximately 14% of patients with a new diagnosis of ALS. Cognitive impairment, predominantly but not exclusively in the form executive dysfunction, is present in more than 40% of ALS patients who have no evidence of dementia. Cognitive impairment in ALS is not a universal feature, and its manifestations may be more heterogeneous than previously recognised.

  • ALS
  • motor neuron disease
  • dementia
  • cognition
  • epidemiology

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  • JP and ME are joint first authors of this paper.

  • Funding The research leading to these results has received funding from the Health Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 259867, ALSA (the ALS Association), HRB (the Health Research Board, grant H01300) and Research Motor Neuron (previously named Motor Neuron Disease Research Foundation).

  • Competing interests None.

  • Patient consent Obtained.

  • Ethical approval Written informed consent was obtained from all participants. The study had full ethical approval from Beaumont Hospital Research Ethics Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.