When assessing potential differences in the site of onset between clusters, we found that in KCL BrainBank, there was a borderline significant difference in the proportion of people with limb-onset SALS assigned to the clusters (X 2 = 6.05, p-value = 0.05).
Telomere length was shorter in cluster three in KCL BrainBank, which despite being non-significant, is also an important trend to investigate as although mounting evidence supports the association between longer telomere length and worsened severity of ALS [ 70 , 71 ], there is also an established link between chronic inflammatory states and telomere shortening in aging and disease [ 72 – 74 ].