(HealthDay News) — Women of European descent are at greater risk of entering menopause early if they smoke and carry particular gene variants, according to a study published online January 20 in Menopause.

Samantha F. Butts, MD, from the University of Pennsylvania in Philadelphia, and colleagues examined the association between smoking, the presence of single nucleotide polymorphisms in four genes involved in the metabolism of environmental chemicals and steroid hormones, and the risk of menopause. Four hundred ten women aged 35–47 years were included in the study.

The researchers found that European-American smokers carrying the CYP3A4*1B or CYP1B1*3 variants were at greater risk of entering menopause, compared with noncarriers. The risk of menopause entry was greater for smokers than nonsmokers among CYP1B1*3 carriers (adjusted hazard ratio, 2.26; median time to menopause, 10.42 and 11.07 years, respectively) and among CYP3A4*1B carriers (adjusted hazard ratio, 15.1; median time to menopause, 11.36 and 13.91 years, respectively). For CYP1B1 wild types, there was no correlation between smoking and menopause, while the risk of menopause entry was far lower in CYP3A4 wild types who smoked (adjusted hazard ratio, 1.59). The greatest risk of menopause entry was seen for heavily smoking CYP1B1*3 and CYP3A4*1B carriers (adjusted hazard ratios, 3.0 and 17.79, respectively).

“Our finding that the risk of menopause entry in European-American smokers varies depending on genetic background represents a novel gene-environment interaction in reproductive aging,” Butts and colleagues conclude.

Two authors disclosed financial ties to Swiss Precision Diagnostics and Forest and Xanodyne Pharmaceuticals.

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