The results from the UMN studies are shown in Table 3. Similar increasing trends in the mean nicotine equivalents and total NNAL were observed with the number of CHRNA5 A alleles in the these replication data sets, although the differences in the means did not reach statistical significance. Because there was no heterogeneity across studies, we combined the three data sets to compute mean nicotine equivalents and total NNAL by CHRNA5 genotype adjusting for cigarettes per day using all subjects. Differences in mean nicotine equivalents and total NNAL were observed, with p-values that were as strong as those for the Hawaii study (Table 3).
