I am currently performing a GWAS using a Illumina genotyping chip and PLINK2.

As part of the preprocessing I looked into the population stratification of my cohort and observed that all individuals come from Europe (which is what I also expected). Nonethless, I included the first 10 principal components as covariates in the linear association model. PLINK2 returned a genomic inflation estimate of `1.00085`

. If I rerun the analysis, but exclude the PC as covariates, I still get a genomic inflation estimate of `1.00159`

which is still very close to 1.

So my question is, if I even need to include the PCs as covariates as it seems like there is no population stratification at all.