Second to fourth digit ratio (2D:4D), breast cancer risk factors, and breast cancer risk: a prospective cohort study
Menée en Australie, cette étude de cohorte prospective incluant 24 469 participantes évalue l'association entre l'indice 2D:4D (rapport des longueurs de l'index et de l'annulaire de la main droite) et le risque de cancer du sein
Background: We aimed to assess whether 2D:4D measures are associated with breast cancer risk. Methods: We derived the ratio of the lengths of the index and ring fingers (2D:4D), and right minus left 2D:4D (
Δr
−l) from digit lengths measured from photocopies of participants’ hands collected during a recent follow-up of the Melbourne Collaborative Cohort Study, a prospective study including 24 469 women. Of the 9044 women with available data, we identified 573 incident breast cancer cases. Hazard ratios (HR) and 95% confidence intervals (CI) for a one standard deviation difference in 2D:4D measures were obtained from Weibull survival models, and linear regression models were used to examine potential associations between 2D:4D measures and age at menarche and menopause. Results: We found a direct association between left 2D:4D and breast cancer risk, an inverse association between
Δr
−l and risk of breast cancer, but no association between right 2D:4D and breast cancer risk. Among breast cancer cases, both right 2D:4D and
Δr
−l were inversely associated with age at diagnosis. We also observed associations between both right 2D:4D and
Δr
−l and age at menopause, with increasing digit ratio measures related to earlier mean age at menopause. Conclusion: Digit ratio measures might be associated with breast cancer risk and age at onset of breast cancer. If confirmed in other studies, this suggests that lower exposure or sensitivity to prenatal testosterone might be associated with lower risk of breast cancer.