Waist circumference, body mass index, and postmenopausal breast cancer incidence in the Cancer Prevention Study-II Nutrition Cohort.
OBJECTIVE
High body mass index (BMI) is an established risk factor for postmenopausal breast cancer. However, less is known about associations with waist circumference. In particular, it is unclear whether a larger waist circumference is associated with risk more than would be expected based solely on its contribution to BMI.


METHODS
We examined the associations of BMI and waist circumference with risk of postmenopausal breast cancer, with and without mutual adjustment, in the Cancer Prevention Study-II Nutrition Cohort. Analyses included 28,965 postmenopausal women who reported weight and waist circumference on a questionnaire in 1997 and were not taking menopausal hormones.


RESULTS
During a median follow-up of 11.58 years, 1,088 invasive breast cancer cases were identified. Hazard ratios (HR) and 95 % confidence intervals (CI) were estimated from multivariable-adjusted Cox proportional hazard regression models. Without adjustment for BMI, a larger waist circumference was associated with higher risk of breast cancer (per 10 cm increase in waist circumference, HR = 1.13, 95 % CI 1.08-1.19). However, adjustment for BMI eliminated the association with waist circumference (per 10 cm HR = 1.00, 95 % CI 0.92-1.08). BMI was associated with risk unadjusted for waist circumference (per 1 kg/m(2) HR = 1.04, 95 % CI 1.03-1.05) and adjusted for waist circumference (per 1 kg/m(2) HR = 1.04, 95 % CI 1.02-1.06).


CONCLUSIONS
Our study of predominantly white women provides evidence that a larger waist circumference is associated with higher risk of postmenopausal breast cancer, but not beyond its contribution to BMI.
Epidemiology Research Program, American Cancer Society, 250 Williams Street NW, Atlanta, GA, 30303, USA, Mia.Gaudet@cancer.org.
Mia M
MM
Gaudet
Brian D
BD
Carter
Alpa V
AV
Patel
Lauren R
LR
Teras
Eric J
EJ
Jacobs
Susan M
SM
Gapstur
D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D017698:Postmenopause; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D055105:Waist Circumference