CHM and dementia: However, this protective effect of REP1 on cognitive decline was not replicated by an Italian study of 426 PD patients which showed that carriers of the REP1–263 allele (similarly linked with PD risk) showed significantly increased risk of dementia compared to carriers of shorter alleles (HR 3.03; p < 0.001)18 or by a Singapore study which showed that REP1–263 allele carriers were associated with lower MMSE scores (β –1.46; p = 0.010)34.