We present here a GWAS of these three traits in a relatively isolated Han Chinese population from Northern Hunan. Due to the combination of physical isolation and low geographic mobility, a large number of related individuals are found in a small region. Such isolated populations may facilitate considerably the identification of susceptibility alleles for complex traits for at least three main reasons: greater linkage disequilibrium (LD) facilitating locus detection even with less-dense GWAS arrays, greater genetic homogeneity resulting from founder effects and/or population bottlenecks, and reduced environmental heterogeneity resulting from a greater degree of shared geographic and cultural factors. This is particularly relevant for studies of AD, where consistency of exposure across the sample is an important factor (Gulcher et al. 2001; Ober et al. 1998; Peltonen et al. 2000). We addressed an important deviation from consistency of exposure between males and females by focusing the analysis on men. The primary limitation of this overall approach is that risk variants (and perhaps genes) underlying disease susceptibility in a specific population or family may not be the same as those contributing
