Association of age at menarche with adult leg length and trunk height: Speculations in relation to breast cancer risk.

BACKGROUND

It seems paradoxical that both increased height and earlier age at menarche (which predicts for shorter stature) are both associated with increased breast cancer risk.

METHODS

Retrospective data from a parental cohort coupled with prospective interviews with and anthropometric measurements from their daughters were used. Multivariable linear regression analyses were conducted using mixed regression models to account for same-family participants.

RESULTS

Controlling for birth weight, maternal height, and birth cohort, and analyzed as a group, a 1-year increase in the age at menarche predicted an increase in standing height, leg length, and trunk height of 0.76, 0.41, and 0.35 cm, respectively. However, when stratifying by birth year (prior to 1966 vs 1966 or after), these relationships were true only for those born prior to 1966.

CONCLUSION

Given the height-breast cancer risk association, the emerging evidence linking breast cell proliferation to hormones associated with growth, and the finding in this study that the relationship between age at menarche and adult height no longer exists for women born in 1966 or later, it is possible that the long-established relationship between age at menarche and breast cancer risk may also no longer exist.