Apathy in amyotrophic lateral sclerosis: systematic review and meta-analysis of frequency, correlates, and outcomes

Objectives: To determine the frequency and correlates of apathy in amyotrophic lateral sclerosis (ALS) and its influence on the prognosis of the disease.Methods: Three databases were searched: MEDLINE, PubMed, and Google Scholar. Quantitative synthesis of the frequency of apathy in ALS was conducted using random effects in Stata (College Station, TX). Meta-regression and subgroup analyses were conducted to investigate the association between frequency of apathy in ALS and different covariates.Results: Fifty-two studies (51 cohorts) were included in the analysis. The pooled frequency of apathy in ALS was 25% (95% confidence interval (CI) 14-35%) according to the studies that used self-rated tools and 34% (95% CI 27-41%) according to studies that used informant-rated tools. The emergence of apathy was associated with cognitive decline and bulbar onset of the disease. There was no consistent relationship between apathy and disease stage or the severity of depression. Structural brain imaging studies established that ALS patients with apathy exhibited more prominent changes with structural and functional brain imaging particularly involving fronto-subcortical regions of the brain. Overall, apathy worsened the long-term prognosis of ALS.Discussion: Apathy affects up to a third of ALS patients аnd develops in the context of progressive neurodegeneration. Increased awareness and understanding of non-motor symptoms in ALS highlights the potential utility of apathy as an outcome measure in future clinical trial design.