© The Author 2007. Published by Oxford University Press.
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Dietary Fat and Postmenopausal Invasive Breast Cancer in the National Institutes of Health–AARP Diet and Health Study Cohort
Affiliations of authors: Nutritional Epidemiology Branch, Division of Cancer Epidemiology and Genetics (ACMT, SCC, ML, AS), Biometry Research Group, Division of Cancer Prevention (VK), Applied Research Program, Division of Cancer Control and Population Sciences (AFS, FET), Biostatistics Branch, Division of Cancer Epidemiology and Genetics (PSR), National Cancer Institute, Bethesda, MD; AARP, Washington, DC (ARH)
Correspondence to: Anne C. M. Thiébaut, PhD, Nutritional Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 6120 Executive Blvd, Executive Plaza South Rm 3033, Bethesda,MD 20892 (e-mail: thiebauta{at}mail.nih.gov).
Background: Although ecologic association and animal studies support a direct effect of dietary fat on the development of breast cancer, results of epidemiologic studies have been inconclusive.
Methods: We prospectively analyzed the association between fat consumption and the incidence of postmenopausal invasive breast cancer in the National Institutes of Health–AARP Diet and Health Study, a US cohort comprising 188 736 postmenopausal women who completed a 124-item food-frequency questionnaire in 1995–1996. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox proportional hazards regression models with adjustment for energy and potential confounding factors. All statistical tests were two-sided.
Results: Over an average follow-up of 4.4 years, the cohort yielded 3501 cases of invasive breast cancer. The hazard ratio of breast cancer for the highest (median intake, 40.1% energy from total fat; 434 cases per 100 000 person-years) versus the lowest (median intake, 20.3% energy from total fat; 392 cases per 100 000 person-years) quintile of total fat intake was 1.11 (95% CI = 1.00 to 1.24; Ptrend = .017). The corresponding hazard ratio for a twofold increase in percent energy from total fat on the continuous scale was 1.15 (95% CI = 1.05 to 1.26). Positive associations were also found for subtypes of fat (hazard ratio for a twofold increase in percent energy from saturated fat = 1.13; 95% CI = 1.05 to 1.22; from monounsaturated fat, HR = 1.12; 95% CI = 1.03 to 1.21; from polyunsaturated fat, HR = 1.10, 95% CI = 1.01 to 1.20). Correction for measurement error in nutrient intakes, on the basis of a calibration substudy that used two 24-hour dietary recalls, strengthened the associations, yielding an estimated hazard ratio for total fat of 1.32 (95% CI = 1.11 to 1.58). Secondary analyses showed that associations between total, saturated, and monounsaturated fat intakes were confined to women who were not using menopausal hormone therapy at baseline.
Conclusion: In this large prospective cohort with a wide range of fat intake, dietary fat intake was directly associated with the risk of postmenopausal invasive breast cancer.
| CONTEXT AND CAVEATS Prior knowledge Ecologic association and animal studies have suggested that high-fat diets contribute to the development of breast cancer. However, epidemiologic studies of the association between dietary fat intake and the risk of breast cancer have been inconclusive. Study design Large prospective cohort study of the association between fat consumption (assessed with the use of a food frequency questionnaire) and the incidence of invasive breast cancer among postmenopausal women with a wide range of fat intake. Contribution A direct association between dietary fat intake—both total fat intake and intakes of the major fat subtypes—and the risk of invasive breast cancer was detected. The authors also found a statistically significant interaction between menopausal hormone use and dietary fat intake with respect to breast cancer risk. Implications The hypothesis that dietary fat increases the risk of invasive breast cancer remains viable and warrants continued investigation. Further studies are needed to examine whether use of menopausal hormone therapy mediates the association between dietary fat intake and the risk of breast cancer. Limitations Unmeasured confounders and measurement error could have influenced the observed associations.
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Manuscript received September 6, 2006; revised January 11, 2007; accepted January 25, 2007.
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J Natl Cancer Inst 2007 99: 418-419.
J Natl Cancer Inst 2007 99: 413.
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