Increasing BMI was associated with increasing risk for overall cancer incidence and mortality in middle-aged women

Question: In middle-aged women, what is the association between body mass index (BMI) and cancer incidence and mortality?

METHODS
Design: Prospective cohort study with mean follow-up of 5.4 years for cancer incidence and 7.0 years for cancer mortality.

Setting: Population-based study in England and Scotland, United Kingdom.

Patients: 1 222 630 women 55 to 64 years of age (mean 56 y) who had no history of cancer at baseline.

Risk factors: BMI at baseline, divided into 5 categories (< 22.5, 22.5 to 24.9, 25.0 to 27.4, 27.5 to 29.9, and ≥ 30 kg/m2).

Outcomes: Cancer incidence and mortality, overall and for 17 specific types of cancer, identified through linkage with the National Health Service central registers.

Main results: Increasing BMI was associated with increasing risks for all cancers, endometrial cancer, esophageal adenocarcinoma, kidney cancer, leukemia, postmenopausal breast cancer, multiple myeloma, pancreatic cancer, non-Hodgkin lymphoma, and ovarian cancer; and with decreasing risks for esophageal squamous cell carcinoma, lung cancer, and premenopausal breast cancer (Table). Risks for stomach, colorectal, cervical, bladder, and brain cancer and malignant melanoma did not vary by BMI. Patterns for cancer mortality were similar to those for cancer incidence: Relative risk for death from any type of cancer was 1.06 (95% CI 1.02 to 1.10) per 10-unit increase in BMI. In postmenopausal women, the estimated proportion of cancer attributable to being overweight or obese (BMI ≥ 25 kg/m2) was 5% for all cancers and about 50% for endometrial cancer and esophageal adenocarcinoma.

Conclusions: In middle-aged women, increasing body mass index was associated with increasing risk for cancer incidence and mortality overall. High body mass index increased risk for some types of cancer but reduced risk for other types.