MSH3 and Mental deterioration: More specifically, participants with one or more 3a alleles in MSH3 had a better cognitive function at baseline and slower cognitive decline compared with non-carriers of 3a alleles [for average age and DBS slope (95% CI) = −0.329 (−0.434, −0.223) and −0.118 (−0.241, 0.004)] for non-carriers and carriers, respectively; contrast estimate (SE) non-carriers versus carriers = −0.21 (0.081), t(213) = −2.587, P = 0.010; Fig. 2A and Supplementary Fig. 4).