Letters Section Editor: Robert M. Golub,
MD, Senior Editor.
To the Editor: I would like to raise some methodological
concerns about the study by Dr Kreijkamp-Kaspers et al.1 First,
their assumption that soy isoflavones are equipotent to conventional hormone
therapy is in error. Their power analysis indicates that they should have
been able to detect a 6.7% increase in bone mineral density (BMD) based on
200 participants. They should have used 2-directional hypothesis testing and
calculated power based on their actual sample size and, given that this magnitude
of increase is within the range previously reported for bisphosphonates,2 a 3% change in response to isoflavones over 1 year
may have been more realistic. Second, the authors state that “adjustment
for smoking history and baseline BMD did not change the results,” but
current smoking status and antihypertensive medication use should have been
taken into account statistically.
Alekel DL. Isoflavones and Postmenopausal Women. JAMA. 2004;292(19):2338-2339. doi:10.1001/jama.292.19.2336-b