Central obesity and breast cancer risk: a systematic review

Abstract

The specific effect of central rather than general obesity on breast cancer risk is not clear. This review examines the relationship between waist and waist-hip ratio (WHR) and risk of breast cancer in pre- and post-menopausal women using all available cohort and case-control data. The databases of the Cochrane Library, Medline, Cancer Lit and Embase were searched until October 2002. Relevant cohort and case-control studies with separate analyses in pre- and/or post-menopausal women were included. Random effects meta-analyses were carried out, subgrouped by pre- or post-menopausal status and cohort or case-control design. Sensitivity analyses were also performed. Five cohort studies with 72,1705 person years of observation (453 pre-menopausal and 2684 post-menopausal cases), and three case-control studies comprising 276 pre-menopausal cases with 758 pre-menopausal controls and 390 post-menopausal cases with 1071 post-menopausal controls were included. Pooled results from cohort studies using the most adjusted data [but without adjustment for weight or body mass index (BMI)] suggest a 39% lower risk of breast cancer in post-menopausal women with the smallest waist (compared with the largest) and a 24% lower risk in women with the smallest WHR. In pre-menopausal women, however, pooled results suggest that measurement of waist or WHR have little effect on risk of breast cancer. Adjustment for BMI abolished the relationship between waist or WHR and risk of post-menopausal breast cancer, but introduced such a relationship amongst pre-menopausal women. The relationship between a smaller measurement of waist or WHR and lower risk of post-menopausal breast cancer appears to result from the associated correlation with BMI. Amongst pre-menopausal women, central (not general) obesity may be specifically associated with an increased risk of breast cancer.

A case‐control study to assess the impact of mammographic density on breast cancer risk in women aged 40–49 at intermediate familial risk

“…In agreement, a positive association between central fat (as a proxy for visceral fat) and breast cancer risk has been suggested in premenopausal women. 44 Overall, these observations may point to a differential effect of visceral fat and breast fatty tissue on risk of breast cancer. Indeed, nondense area has been suggested as a potential marker for age-related lobular involution of the breast which is inversely associated with breast cancer risk independently of density, and strongly positively associated with absolute nondense area.…”

“…24 Absolute dense area may also be a better endpoint to use in randomised controlled trials assessing the impact of various interventions on breast density: absolute density was indeed found to be more sensitive than percent density to the implementation of a low-fat high carbohydrate diet for a period of 2 years. 40 Due to the targeted age range (40)(41)(42)(43)(44)(45)(46)(47)(48)(49), the majority of women in our study were premenopausal. We did not observe any correlation between age at mammogram and absolute area of dense or nondense tissues in this subset of women.…”

“…After adjusting for absolute nondense area, every additional 10 cm 2 of dense tissue was associated with a 7% increase in odds of breast cancer in all women (n 5 292, actual age range [40][41][42][43][44][45][46][47][48][49][50], but with a 14% increase in premenopausal women (n 5 200, actual age range [40][41][42][43][44][45][46][47][48][49][50]. MD may therefore be an even more important risk factor in premenopausal compared to postmenopausal women among those at higher-thanaverage risk not currently within screening age range.…”

Adiposity and breast cancer risk in postmenopausal women: Results from the UK Biobank prospective cohort

“…A 2003 review on central obesity found that waist circumference and waist‐to‐hip ratio were no longer associated with postmenopausal breast cancer risk after adjusting for BMI or weight,28 and some subsequent studies showed similar results 13, 29, 30. However, a recent meta‐analysis found that the association between waist circumference and postmenopausal breast cancer risk was only slightly attenuated after adjusting for BMI 9.…”

Estrogens, Obesity, Inflammation, and Breast Cancer—What Is the Link?

“…In postmenopausal life, this appears to be due primarily to an increased capacity of adipose tissue to synthesize estrogens as a function of age 15,16 ; however, the mechanism of this increase is not entirely understood at this time. 17,18 While it is facile to say that obesity may be reversed or prevented by healthy diet and exercise, most individuals who are obese find it difficult to achieve permanent loss of weight by these methods; hence, other therapeutic interventions are required to stave off a global epidemic of breast cancer arising from the obesity pandemic.…”