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Understanding recent trends in incidence of invasive breast cancer in Norway: age-period-cohort analysis based on registry data on mammography screening and hormone treatment use

BMJ 2012; 344 doi: http://dx.doi.org/10.1136/bmj.e299 (Published 30 January 2012) Cite this as: BMJ 2012;344:e299

Re: Understanding recent trends in incidence of invasive breast cancer in Norway: age-period-cohort analysis based on registry data on mammography screening and hormone treatment use

Dear Editor,

The authors have informed me that 20 years ago there was a paper in JAMA using this method (1). Unfortunately, I did not find this paper when searching. More important is that recently there has been published another RCT showing no effect of hormone replacement therapy on the risk of breast cancer (2). In medicine we should rely on RCT and not on speculative statistical analysis which hardly any readers of BMJ do understand.

1. Weissman MM, Wickramaratne P, Greenwald S, et al. The Changing Rate of Major Depression: Cross-National Comparisons. JAMA. 1992; 268(21): 3098-3105.

2. Schierbeck LL, Rejnmark L, Tofteng CL, et al. Effect of hormone replacement therapy on cardiovascular events in recently postmenopausal women: randomised trial. BMJ 2012; 345: e6409

Competing interests: No competing interests

19 December 2012
Per-Henrik Zahl
Senior scientist
Norwegian Institute of Public Health
PO Box 4404 Nydalen, N-0403 Oslo, Norway
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