Presenilin gene predisposes to late-onset degenerative but not vascular dementia: A comparative study of PS1 and ApoE genes in a North Indian cohort

Background: Variation in the presenilin gene shifts the cleavage site of amyloid precursor protein producing an insoluble peptide A beta(42) ( instead of A beta(40), which is soluble when produced in restricted amount), which is prone to aggregation in the brain in the form of amyloid plaques not only in Alzheimer's disease (AD) but also in other degenerative dementias. The role of presenilin 1 (PS1) and apolipoprotein E ( ApoE) genes has not been explored in degenerative dementias other than AD. Objective: To study the association of PS1 intron 8 and ApoE epsilon 4 gene polymorphism in degenerative and vascular dementia patients in the North Indian population. Design: A hospital-based association study on degenerative and vascular dementia patients proven on the basis of clinical profile and MRI. Participants: A group of 107 dementia patients and 162 age- and sex-matched controls from a North Indian cohort participated in the study. All patients had Mini Mental State Examination scores less than 24 and met the DSM-IV criteria for dementia. Results: The frequency of genotype 1/1 and allele 1 in degenerative dementias (73.12 and 83.70%, respectively) was higher than what had been reported so far in AD. A significant association of PS1 intron 8 polymorphism was found with degenerative dementias but not with vascular dementias ( OR 2.50, 95% Cl 1.27-5.00). On the other hand, ApoE epsilon 4 allele was found to significantly increase the risk for both vascular and degenerative dementias ( p = 0.0001, OR 3.45, 95% Cl 1.74-6.86). Conclusion: While ApoE epsilon 4 allele increases the susceptibility to both degenerative and vascular dementia, PS1 allele 1 increases the susceptibility to degenerative dementias only.