Abstract
Background. Although individual metabolic risk factors are reported to be associated with breast cancer risk, controversy surrounds risk of breast cancer from metabolic syndrome (MS). We report the first systematic review and meta-analysis of the association between MS and breast cancer risk in all adult females. Methods. Studies were retrieved by searching four electronic reference databases [PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Web of Science, and ProQuest through June 30, 2012] and cross-referencing retrieved articles. Eligible for inclusion were longitudinal studies reporting associations between MS and breast cancer risk among females aged 18 years and older. Relative risks and 95% confidence intervals were calculated for each study and pooled using random-effects models. Publication bias was assessed quantitatively (Trim and Fill) and qualitatively (funnel plots). Heterogeneity was examined using Q and I 2 statistics. Results. Representing nine independent cohorts and 97,277 adult females, eight studies met the inclusion criteria. A modest, positive association was observed between MS and breast cancer risk (RR: 1.47, 95% CI, 1.15–1.87; z = 3.13; p = 0.002; Q = 26.28, p = 0.001; I 2 = 69.55%). No publication bias was observed. Conclusions. MS is associated with increased breast cancer risk in adult women.
Highlights
Breast cancer, the most common cancer in women worldwide, accounted for 1.7 million new cases in 2012, comprising a quarter of all new cancer cases [1]
A statistically significant increase of 47% in the risk for incident breast cancer was observed for adult females with metabolic syndrome (MS) (RR: 1.47, 95% confidence intervals (CIs), 1.15– 1.87; z = 3.13; p < 0.002; Q = 26.28, p < 0.001; I2 = 69.55%) (Figure 2)
Using the Trim and Fill approach that resulted in two imputations, the risk decreased by 16% but remained significant (RR: 1.31, 95% CI, 1.01–1.70)
Summary
The most common cancer in women worldwide, accounted for 1.7 million new cases in 2012, comprising a quarter of all new cancer cases [1]. While traditional risk factors for breast cancer include age, family history of cancer, and reproductive and menstrual history, the National Cancer Institute recognizes overweight, lack of physical activity, and consumption of alcohol as risk factors [2] Several of these risk factors are associated with metabolic syndrome [3]. The NCEP ATP III guidelines are the most commonly used criteria in the US [6] These criteria include the presence of three or more of the following [3]: abdominal obesity (waist circumference ≥ 35 inches in women), triglycerides ≥ 150 mg/dL, high density lipoprotein cholesterol (HDL-C) < 50 mg/dL, blood pressure (BP) ≥ 130/85 mmHg, and fasting glucose ≥ 110 mg/dL. Eligible for inclusion were longitudinal studies reporting associations between MS and breast cancer risk among females aged 18 years and older. MS is associated with increased breast cancer risk in adult women
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