Among the remaining five array-based studies that did not replicate an association between smoking and cg05575921, two used a distinct cell type (buccal scrapings, fetal lung and placenta) [62,63], one examined newborns exposed in-utero [64], and in another, the probe was associated at p < 1 × 10−4 but did not reach statistical significance. The remaining study, no probes showed any significant associations (likely due to low power), but among all probes tested, probe cg05575921 was the most significantly associated [29]. Thus, findings of significant association between smoking and hypomethylation of cg05575921 have been the rule rather than the exception.
