Additionally, a common haplotype at CHRNA5 and CHRNA3 increased risk across a series of ND-related phenotypes among European-origin populations, including ND [88,89,91,92,95], early-onset ND [96,97], CPD [98], FTND score [89,96], inability to quit when pregnant [99], serum cotinine (a nicotine metabolite) level [95,100], and chronic obstructive pulmonary disease [101]. Here, CHRNA5 is linked to chronic obstructive pulmonary disease.