Objective: To determine whether cognitive status in patients with amyotrophic lateral sclerosis (ALS) is a useful predictor of attrition and motor and cognitive decline.
Methods: Cognitive testing was undertaken in a large population-based cohort of incident ALS patients using a longitudinal, case-control study design. Normative data for neuropsychological tests were generated using age-, sex-, and education-matched healthy controls who also underwent repeated assessments. Data were analyzed to generate models for progression/spread.
Results: One hundred eighty-six patients with ALS who had no evidence of C9orf72 hexanucleotide repeat expansion were enrolled. A second and third assessment were undertaken in 98 and 46 of the patients with ALS, respectively. Executive impairment at the initial visit was associated with significantly higher rates of attrition due to disability or death and faster rates of motor functional decline, particularly decline in bulbar function. Decline in cognitive function was faster in patients who were cognitively impaired at baseline. Normal cognition at baseline was associated with tendency to remain cognitively intact, and with slower motor and cognitive progression.
Conclusions: Non-C9orf72-associated ALS is characterized by nonoverlapping cognitive subgroups with different disease trajectories. These findings have important implications for models of ALS pathogenesis, and for future clinical trial design.