Researchers affiliated with the UK Million Women Study have reported that increasing body mass index (BMI) is associated with an increased risk of 10 specific types of cancer out of 17 evaluated. The details of this study appeared in an early on-line publication on November 6, 2007 in the British Medical Journal.¹

Obesity has been associated with an increased incidence of several cancers and obesity also leads to an increased death rate in patients with cancer. However, the exact extent of these relationships is unknown. Researchers in the UK evaluated the incidence of cancer and deaths from cancer in 1.2 million women between the ages of 50 and 64 who were followed since recruitment between 1996 and 2001. The average follow-up was 5.4 years. During this period of time there were 45,037 cases of cancer and 17,203 deaths from cancer. BMI was categorized into 5 different groups: <22.5, 22.5-24.9, 25-27.4, 27.5-29.5 and >30 kg/m2 with 22.5-24.9 kg/m2 being the normal reference BMI group for defining relative risk (RR).

Increasing body mass index was associated with an increased incidence of and death from ten cancers. These ten cancers are listed below along with the trend in relative risk (RR) per 10 units of BMI:

Increasing BMI did not affect the incidence or deaths from squamous cell carcinoma of the esophagus, gastric cancer, postmenopausal colorectal cancer, melanoma, premenopausal breast cancer, cervical cancer, bladder cancer or brain cancer. These authors also reported that an increasing BMI was associated with a lower incidence of lung and squamous cell carcinoma of the esophagus.

These authors estimated that 5% of all cancers among postmenopausal women in the UK could be attributed to being overweight or obese which represents 6,000 new cases of cancer per year.

Comments: These are interesting findings that, in general, confirm other studies in smaller groups of women.

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Reference:

¹ Reeves GK, Pirie K, Beral V, et al. Cancer incidence and mortality in relation to body mass index in the Million women Study: cohort study. British Medical Journal 2007; early on-line publication on November 6.