The short variant of the polymorphism within the promoter region of the serotonin transporter gene is a risk factor for late onset Alzheimer's disease.

We analyzed a deletion/insertion polymorphism within the promoter region of the serotonin transporter gene (5-HTTPLR) in 81 patients with late onset Alzheimer's (AD) disease (mean age 70.02 +/- 8.13 years). Control groups included 81 normal subjects with comparable age (mean age 75.6 +/- 10.2) and 82 younger normal subjects (mean age 37.4 +/- 9.1). Statistical analysis showed a significant difference in the genotype and gene frequencies between the AD group and normal controls (chi 2 = 9.021; 2 d.f. and chi 2 = 5.59, 1 d.f., respectively, P < 0.05) due to the higher frequency of the L allele and the lower frequency of the s allele in controls than among AD patients. However, no differences were found in the genotype frequencies in older as compared to younger normal control groups (chi 2 = 0.337, 2 d.f. and P > 0.05). The present study confirms, in a different population, that the short variant of the 5-HTTPLR polymorphism may be a risk factor for late onset AD.