C9 and amyotrophic lateral sclerosis: A case-control study assessed the effect of lifestyle factors on causation stratified by the C9orf72 mutation.28 The authors found that daily energy intake at symptom onset was higher in the C9-positive (712 kJ, 95% CI 212–1213, P = 0.0053) and C9-negative groups (497 kJ, CI 295–700, P < 0.0001), concluding that a combination of increased PA and an underlying C9orf72 mutation can increase the risk of developing ALS.