title: Reductions in use of hormone replacement therapy: effects on Swedish breast cancer incidence trends only seen after several years.
abstract: Studies from Western countries have found evidence of a recent decline in breast cancer incidence rates in postmenopausal women, findings which have been hypothesized to reflect a reduced use of hormonal replacement therapy (HRT). We examined breast cancer incidence trends in Sweden between 1997 and 2007, a period characterized by a drop in the use of HRT. Incidence trends were assessed using data from three population-based Regional Clinical Registries on breast cancer covering 2/3 of the Swedish population. Information on HRT sales was obtained from national pharmacy data. The prevalence of HRT use in age group 50-59 years decreased from a peak of 36% in 1999 to 27% in 2002 and further to 9% in 2007. Incidence rates of breast cancer in women 50 years and older increased between 1997 and 2003. A significant decrease in incidence between 2003 and 2007 was confined to women 50-59 years of age, the group in which the prevalence of HRT use has been highest and the decrease in use most pronounced. As opposed to the immediate effects reported from the United States and other regions, there was a time lag between the drop in HRT use and clear reductions in breast cancer incidence. This may reflect between country differences with regard to types of HRT used, and the rate, magnitude and pattern of change in use. The present findings give further support to the notion that HRT use is a driver of breast cancer incidence trends on the population level.
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, PO Box 281, 171 77 Stockholm, Sweden. Mats.Lambe@ki.se
authors.forename: Mats
authors.initials: M
authors.lastname: Lambe
authors.forename: Annette
authors.initials: A
authors.lastname: Wigertz
authors.forename: Marit
authors.initials: M
authors.lastname: Holmqvist
authors.forename: Jan
authors.initials: J
authors.lastname: Adolfsson
authors.forename: Carola
authors.initials: C
authors.lastname: Bardage
authors.forename: Tommy
authors.initials: T
authors.lastname: Fornander
authors.forename: Per
authors.initials: P
authors.lastname: Karlsson
authors.forename: Viveca
authors.initials: V
authors.lastname: Odlind
authors.forename: Ingemar
authors.initials: I
authors.lastname: Persson
authors.forename: Johan
authors.initials: J
authors.lastname: Ahlgren
authors.forename: Leif
authors.initials: L
authors.lastname: Bergkvist
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology*; D015914:Estrogen Replacement Therapy / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D013548:Sweden / Q000453:epidemiology