C9orf72 and frontotemporal dementia: C9orf72 expansion size was not significantly associated with age of first ALS or FTD diagnosis or age of death in people with ALS or FTD but increased with age at study entry in C9orf72 HRE carriers (beta = 4.5 repeats/year, 95% CI 1.9–5.2, P < 0.001; Fig. 2).