In a retrospective cohort of 275 ALS patients, higher Hb and hematocrit levels were associated with increased odds of death or tracheostomy (odds ratio for Hb = 1.71; 95% CI: 1.24–2.36); however, given its observational design, this study cannot establish causality (Mandrioli, Rosi et al. This evidence concerns the gene GSTM1 and amyotrophic lateral sclerosis.