C9orf72 and amyotrophic lateral sclerosis: Multivariate Cox survival analysis identified a significant association between pathogenic C9orf72 expansions (≥30 repeat units) and reduced ALS survival (HR = 1.51, 95% CI = 1.34–1.71, P = 2.37 × 10−11), with carriers living on average 11.5 months less corresponding to a median survival difference of 3.8 months (Fig. 3B, Fig. S17, Tables S20 and S21).