In 8 of the 21 studies that assessed the association between 36 SNCA polymorphisms and cognition, 4 SNPs27,31,35,37,39 and the REP1 polymorphism18,34,38 were shown to be significantly associated with measures of cognitive impairment or the diagnosis of dementia (Fig. 2 and Supplementary Table 3). The gene discussed is CHM; the disease is dementia.