at the CHRNA5/CHRNA3/CHRNB4 locus. A fourth meta-analysis [Saccone et al., 2010a] focused on four statistically distinct loci in the CHRNA5/CHRNA3/CHRNB4 cluster tagged by SNPs rs16969968 (CHRNA5), rs578776 (CHRNA3), rs588765 (CHRNA5), and rs12914008 (CHRNB4) [Saccone et al., 2009a]. SNPs rs16969968 and rs588765 were each strongly associated with CPD in a joint model that adjusts for the effect of each, suggesting independent effects; rs578776 is also associated with CPD, but its effect size is smaller after adjustment for SNP rs16969968 in the association model [Saccone et al., 2010a].
