Case-control studies of PON1 genetic variants in Alzheimer's disease (AD) and Parkinson's disease (PD) have revealed some positive albeit inconsistent associations with 2 PON1 coding polymorphisms: Q192R (rs662) and L55M (rs854560).
Meta-analyses of studies in Caucasians assessing the associations between the PON1 M55L, -161C/T and Q192R SNPs and the risk of AD were performed, and no associations were found.
The L55M Met allele exerts an AD risk-enhancing effect only in men (P < 0.001), whereas both men and women carrying the M55M/Q192Q genotype exhibit increased survival (2.5 years, P < 0.05) and later age of onset (1.5 years, P < 0.05).
The frequency of the M55M genotype at the PON1 L55M locus was found to be significantly increased in AD patients relative to age-matched controls (p < 0.05).