In the subjects with three night shifts, SNPs in BMAL1 (rs2278749), BMAL2 (rs2306074), CSNK1E (rs5757037), NPAS2 (rs17024926), PER3 (rs1012477) and MTNR1A (rs131113549) were associated with decreased breast cancer risk. This evidence concerns the gene NPAS2 and breast cancer.