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

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

19 December 2012

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: None declared

Per-Henrik Zahl, Senior scientist

Norwegian Institute of Public Health, PO Box 4404 Nydalen, N-0403 Oslo, Norway

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