Variants in the CHRNA@-CHRNA@-CHRNB@ locus , including rs@ , a nonsynonymous variant in CHRNA@ , are genomewide association study-significantly associated with CO ( = @ ; @ % confidence interval -LSB- CI -RSB- , @-@ @ ; P = @ @ ( -@ ) ) , and this association remains strong after adjusting for smoking behavior ( = @ ; @ % CI , @-@ @ ; P = @ @ ( -@ ) ) .