SNP association studies in Alzheimer's disease highlight problems for complex disease analysis.

Genetic linkage and association analyses are two distinct approaches to understanding the genetic etiology of complex disease. Association analysis has become particularly popular in recent times, but the true utility of the strategy remains uncertain. To try to gain better insight into the relevant issues, we have used genetic association analysis to explore the etiology of Alzheimer's disease. Our empirical findings supplement the theoretical debate, illustrating the general doubtfulness of previous positive findings and the limited ability of typical association studies based on candidate genes to discern true medium-sized signals from false positives. Improvements in genotyping technologies and increasing the number of SNPs tested, without sophisticated allowance for all other issues, could simply lead to an unmanageable overload of false-positive signals, themselves obscuring true disease associations.