BackgroundSeveral studies have examined the relationship between body mass index (BMI) and survival from amyotrophic lateral sclerosis (ALS). Many indicate that low BMI at diagnosis or during follow-up may be associated with accelerated progression and shortened survival. This study systematically evaluated the relationship between BMI and survival in patients with ALS.MethodsThe PubMed database was searched to identify all available studies reporting time-to-event data. Eight studies with 6,098 patients fulfilled the eligibility criteria. BMI was considered a continuous and ordered variable. Interstudy heterogeneity was assessed by the Cochran Q test and quantified by the I² metric. Fixed- or random-effects odds ratios summarized pooled effects after taking interstudy variability into account. Significance was set at p < 0.05.ResultsThe ALS survival hazard ratio (HR) decreased approximately by 3% (95% confidence interval [CI]: 2%–5%) for each additional BMI unit when BMI was considered a continuous variable. When BMI was considered a categorical variable, the HRs for “normal” BMI vs “overweight” BMI and “obese” BMI were estimated to be as high as 0.91 (95% CI: 0.79–1.04) and 0.78 (95% CI: 0.60–1.01), respectively. The HR for the comparison of the “normal” BMI vs “underweight” BMI was estimated to be as high as 1.94 (95% CI: 1.42–2.65).ConclusionsBMI is significantly and inversely associated with ALS survival.