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...