Defining menopausal status in epidemiologic studies: A comparison of multiple approaches and their effects on breast cancer rates

Phipps, Amanda I.; Ichikawa, Laura; Bowles, Erin J.A.; Carney, Patricia A.; Kerlikowske, Karla; Miglioretti, Diana L.; Buist, Diana S.M.

doi:10.1016/j.maturitas.2010.04.015

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Volume 67, Issue 1 , Pages 60-66, September 2010

Defining menopausal status in epidemiologic studies: A comparison of multiple approaches and their effects on breast cancer rates

Amanda I. Phipps
- University of Washington, Epidemiology Department, 1959 NE Pacific Street, Health Sciences Building F-262, Box 357236, Seattle, WA 98195-7236, USA
- Corresponding author. Tel.: +1 206 667 2878; fax: +1 206 667 5948.
Laura Ichikawa
- Group Health Research Institute, 1730 Minor Avenue, Suite 1600, Seattle, WA 98101-1448, USA
Erin J.A. Bowles
- Group Health Research Institute, 1730 Minor Avenue, Suite 1600, Seattle, WA 98101-1448, USA
Patricia A. Carney
- Department of Family Medicine, Oregon Health Sciences University, 3181 S.W. Sam Jackson Park Road, Mail Code: FM, Portland, OR 97239-3098, USA
- Department of Public Health and Preventive Medicine, Oregon Health Sciences University, 3181 S.W. Sam Jackson Park Road, Mail Code: FM, Portland, OR 97239-3098, USA
Karla Kerlikowske
- Department of Medicine, University of California, San Francisco, San Francisco Veterans Affairs Medical Center, 111A1, 4150 Clement Street, San Francisco, CA 94121, USA
- Department of Epidemiology, University of California, San Francisco, San Francisco Veterans Affairs Medical Center, 111A1, 4150 Clement Street, San Francisco, CA 94121, USA
- Department of Biostatistics, University of California, San Francisco, San Francisco Veterans Affairs Medical Center, 111A1, 4150 Clement Street, San Francisco, CA 94121, USA
Diana L. Miglioretti
- Group Health Research Institute, 1730 Minor Avenue, Suite 1600, Seattle, WA 98101-1448, USA
- University of Washington, Department of Biostatistics, F-600, Health Sciences Building, 1705 NE Pacific Street, Seattle, WA 98195-7232, USA
Diana S.M. Buist
- University of Washington, Epidemiology Department, 1959 NE Pacific Street, Health Sciences Building F-262, Box 357236, Seattle, WA 98195-7236, USA
- Group Health Research Institute, 1730 Minor Avenue, Suite 1600, Seattle, WA 98101-1448, USA

Received 19 February 2010; received in revised form 21 April 2010; accepted 26 April 2010. published online 13 May 2010.

Abstract

Objectives

Menopausal status is a common covariate in epidemiologic studies. Still, there are no standard definitions for menopausal status using observational data. This study assesses distinctions between menopausal status definitions using commonly collected epidemiologic data, and explores their impact on study outcomes using breast cancer rates as an example.

Study design

Using survey data from 227,700 women aged 40–64 who received screening mammograms from the Breast Cancer Surveillance Consortium, we classified menopausal status under five different definitions: one complex definition combining multiple variables, two definitions using age as a proxy for menopausal status, one based only on menstrual period status, and one based on age and menstrual period status.

Main outcome measures

We compared the distribution of menopausal status and menopausal status-specific breast cancer incidence and detection rates across definitions for menopausal status.

Results

Overall, 36% and 29% of women were consistently classified as postmenopausal and premenopausal, respectively, across all definitions. Menopausal status-specific breast cancer incidence and detection rates were similar across definitions. Rates were unchanged when information regarding natural menopause, bilateral oophorectomy, hormone therapy, and timing of last menstrual period were sequentially added to definitions of postmenopausal status.

Conclusions

Distinctions in menopausal status definitions contribute to notable differences in how women are classified, but translate to only slight differences in menopausal status-specific breast cancer rates.

Keywords: Menopause, Breast cancer, Incidence, Concordance