American Journal of Epidemiology Advance Access published online on August 13, 2007
American Journal of Epidemiology, doi:10.1093/aje/kwm162
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Original Contribution |
Differential Dietary Nutrient Intake according to Hormone Replacement Therapy Use: An Underestimated Confounding Factor in Epidemiologic Studies?
1 INSERM, ERI 20, EA 4045, and Institut Gustave Roussy, Villejuif, France
2 INSERM, U888, Montpellier, France
3 Université Montpellier1, Montpellier, France
4 INSERM, U822, Le Kremlin Bicetre, France
5 Université Paris-Sud, Faculté de Médecine, Le Kremlin Bicetre, France
6 INED, U14, Le Kremlin Bicetre, France
Correspondence to Marie-Noël Vercambre, ERI-20, INSERM, 39, rue Camille Desmoulins, IGR, Espace Tubiana, 94805 Villejuif cedex, France (e-mail: vercambre{at}igr.fr).
Received for publication August 17, 2006. Accepted for publication July 3, 2007.
Observational studies and randomized controlled trials have produced divergent results concerning the effect of hormone replacement therapy (HRT) on cardiovascular disease and, to a lesser extent, dementia. Residual confounding (confounding that remains even after adjustment for various socioeconomic and lifestyle factors) is one explanation that has been offered for these divergent results. The authors used data collected between 1990 and 1995 from 6,697 French women aged 61–72 years participating in a prospective cohort study to explore the hypothesis that nutritional intake varies according to HRT use and thus may be a source of residual confounding. After the authors adjusted for health and lifestyle factors, HRT users, compared with never users, had significantly higher intakes of alcohol; 
3 fatty acids; vitamins B6, B12, and D; and phosphorus and a lower intake of starch. These differential nutrient intakes were related to differences in eating habits. In particular, HRT users in the studied sample, compared with nonusers, ate significantly more fish. Most of the dietary differences were seen in both early users and delayers of HRT. To limit residual confounding in observational studies, dietary factors may be important parameters to be taken into account in analyses of HRT use and health outcomes.
bias (epidemiology); cohort studies; confounding factors (epidemiology); diet; hormone replacement therapy; nutritional status; observation; randomized controlled trials
Abbreviations: HRT, hormone replacement therapy