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The cathepsin D gene (CTSD) exon 2 (C224T) polymorphism has been associated with an increased risk for sporadic Alzheimer's disease (AD), but with controversial findings. We studied CTSD exon 2 (C224T) and apolipoprotein E (APOE) genotype frequencies in 168 AD patients and 218 age-matched healthy controls from Southern Italy. No statistically significant differences were found in CTSD allele or genotype frequencies between AD patients and controls, and there were no interactions with sex or APOE genotype. Furthermore, comparing our results with the findings from other European populations, the CTSD*T allele frequency showed a statistically significant increasing trend from Northern to Southern regions of Europe in AD patients and controls (z=2.51, p<.01; z=4.02, p<.001, respectively), with a concomitant inverse trend for CTSD*C allele frequency. The regional differences in CTSD allele frequencies could be related to the different patterns of association between this polymorphism and AD in various European studies.

Apolipoprotein E (apoE) polymorphism was studied in 79 sporadic late onset Alzheimer's disease (LOAD) patients, 125 unrelated caregivers or volunteers (19-80 years), and 67 centenarians from Apulia, Southern Italy. The frequency of apoE epsilon2 allele was higher in centenarians than in LOAD patients, while epsilon4 was lower. In middle-aged adults, the epsilon4 allele frequency was higher than in centenarians. The epsilon4 allele frequency was lower in healthy adults than in LOAD patients, while epsilon2 was higher. Compared with the allele frequencies of Northern and Central European countries, a geographic trend for epsilon3 and epsilon4 alleles in LOAD and middle-aged adults was observed. The frequency of epsilon3 increased from Northern to Southern Europe, while epsilon4 decreased significantly. In centenarians, epsilon2 showed a North-South increasing pattern, while epsilon4 was in opposite trend.