Letters Section Editor: Stephen J. Lurie,
MD, PhD, Senior Editor.
In Reply: In response to Dr Mao, we recognize
that anorexia nervosa is a serious and potentially life-threatening disease.
We did not intend to imply that women should resort to anorexia as a measure
of preventing breast cancer. Understanding the role of caloric restriction
in the etiology of cancer, particularly breast cancer, is important for disentangling
the puzzle of breast-cancer causation.
We do not share Mao's concern about competing rates. The analytic model
used prevents such bias since it is based on a person-time denominator. A
cohort member only contributes person-time at risk until she is censored from
the analysis (due to a diagnosis of breast cancer, emigration, death, or the
end of follow-up, whichever occurs first). If the risk of dying prematurely
was associated with an excess risk of breast cancer, our results could have
been biased; however, there is no known biological mechanism to
support this hypothesis.
Michels KB, Ekbom A. Risks and Benefits of Severe Caloric Restriction—Reply. JAMA. 2004;291(22):2704. doi:10.1001/jama.291.22.2704-b