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Canadian Journal of Public Health

, Volume 101, Issue 5, pp 405–409 | Cite as

Could Recent Decreases in Breast Cancer Incidence Really Be Due to Lower HRT Use? Trends in Attributable Risk for Modifiable Breast Cancer Risk Factors in Canadian Women

  • C. Ineke NeutelEmail author
  • Howard Morrison
Quantitative Research
  • 1 Downloads

Abstract

Objectives

Recent downward trends in breast cancer incidence have been attributed to declining use of hormone replacement therapy (HRT). To determine whether this is a credible conclusion, this study calculated population attributable risk (PAR) for HRT and other modifiable breast cancer risk factors.

Methods

PAR calculation needs both the prevalence of a risk factor, and the relative risk (RR) for breast cancer incidence for that risk factor. Prevalences were calculated for Canadian women, aged 50–69, participating in the National Population Health Survey, 1994–2006. RR were derived from published research: 1.4 for HRT use, 1.4 for excessive alcohol use, 1.15 for physical inactivity, 1.25 for smoking, 1.4 for BMI over 30 kg/m2. Trends for PAR were calculated for the risk factors separately, as well as combined. Age-adjusted breast cancer incidence rates were calculated for Canadian women aged 50–69 for the years 1994–2004.

Results

Between 1998 and 2004, PAR for HRT decreased by 50%. PAR for other risk factors showed only small changes, and the combined PAR decreased by 18.6%. Age-adjusted breast cancer incidence for women aged 50–69 peaked in 2000 at 330.0/100,000, then dropped by 17.2% by 2004.

Conclusion

Patterns of PAR for HRT use in Canada are consistent with the noticeable decrease in breast cancer incidence observed for women of the same age group. Combining PAR for all risk factors indicated that changes in HRT use overpowered any trends of other risk factors. The combined PAR suggest that alterations in lifestyle could have considerable impact on breast cancer incidence.

Key words

Breast cancer incidence population attributable risk hormone replacement therapy alcohol physical activity obesity 

Résumé

Objectifs

Les tendances à la baisse récemment observées dans l’incidence du cancer du sein ont été attribuées à la diminution de l’usage du traitement hormonal substitutif (THS). Pour déterminer la crédibilité d’une telle conclusion, la présente étude a calculé la fraction étiologique du risque (FER) pour le THS et d’autres facteurs de risque modifiables du cancer du sein.

Méthode

La FER combine la prévalence d’un facteur de risque dans la population avec le risque relatif de l’incidence du cancer du sein associée à ce facteur de risque. Les prévalences ont été calculées chez les Canadiennes de 50 à 69 ans ayant participé à l’Enquête nationale sur la santé de la population (1994–2006). Les risques relatifs ont été tirés des résultats de recherche publiés: 1,4 pour l’utilisation du THS; 1,4 pour la consommation excessive d’alcool; 1,15 pour l’inactivité physique; 1,25 pour l’usage du tabac et 1,4 pour un IMC supérieur à 30 kg/m2. Les tendances de la FER ont été calculées pour les facteurs de risque pris séparément d’abord, puis combinés. Les taux d’incidence du cancer du sein normalisés selon l’âge ont été calculés pour les Canadiennes de 50 à 69 ans, de 1994 à 2004.

Résultats

De 1998 à 2004, la FER du THS a diminué de 50 %. Les FER des autres facteurs de risque pris séparément présentaient de légères variations, alors que la FER de tous les facteurs de risque combinés a diminué de 18,6 %. L’incidence du cancer du sein normalisée selon l’âge chez les femmes de 50 à 69 ans a culminé en 2000, avec un taux de 330,0/100 000; en 2004, ce taux avait diminué de 17,2 %.

Conclusion

Les tendances de la FER du THS au Canada correspondent à la diminution considérable de l’incidence du cancer du sein observée chez les femmes du même groupe d’âge. La FER des facteurs de risque combinés indiquait que des changements apportés au THS surpassaient toute tendance des autres facteurs de risque. Ce résultat laisse également croire qu’une modification des habitudes de vie pourrait avoir des répercussions importantes sur l’incidence du cancer du sein.

Mots clés

incidence du cancer du sein fraction étiologique du risque traitement hormonal de substitution alcool activité physique obésité 

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Copyright information

© The Canadian Public Health Association 2010

Authors and Affiliations

  1. 1.Department of Epidemiology and Community MedicineUniversity of OttawaOttawaCanada
  2. 2.Centre for Chronic Disease Control and PreventionPublic Health Agency of CanadaOttawaCanada

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