Reconciling clinical importance and statistical significance in GWAS

Genome-wide association studies (GWAS) have identified many risk-associated SNPs with very small effects. The mantra for identifying more associations is to greatly increase the sample size to be able to detect smaller and smaller effects. This wonderful letter in the European Journal of Human Genetics points out that at some point the effect size goes below the measurement error calling into question the clinical significance of these GWAS hits. If I were funding a big GWAS study I would first want to know whether increasing the sample size is justified given the effects sizes to be detected and the error of the phenotype measures.

Shriner D, Adeyemo A, Rotimi CN. Reconciling clinical importance and statistical significance. Eur J Hum Genet. 2014 Feb;22(2):158-9. [EJHG]