Abstract
BACKGROUND: Several 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. METHODS: The 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 I(2) metric. Fixed- or random-effects odds ratios summarized pooled effects after taking interstudy variability into account. Significance was set at p < 0.05. RESULTS: The 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). CONCLUSIONS: BMI is significantly and inversely associated with ALS survival.