Adult height in relation to risk of cancer in a cohort of Canadian women.

Although the influence of body mass index on cancer risk has been intensively investigated, few epidemiologic studies have examined the association of adult height with risk of cancer. We assessed the association of height with risk of all cancer and of 19 site-specific cancers in the Canadian National Breast Screening Study, a prospective cohort of nearly 90,000 women. Weight and height were measured at enrollment, and information on reproductive and medical history as well as lifestyle exposures was obtained by means of questionnaire. After exclusions, 5,679 incident invasive cancers were identified among 88,256 women. We used Cox proportional hazards model to estimate hazard ratios (HRs) and 95% confidence intervals (95% CI) per 10 cm increase in height. All tests of statistical significance were two sided. All cancers combined and ten specific sites (colorectum, colon, premenopausal breast, postmenopausal breast, endometrium, ovary, kidney, thyroid, melanoma and leukemia) showed statistically significant positive associations with height. The HR for all cancers combined was 1.13 (95% CI: 1.08-1.18), and the magnitude of the associations for specific sites ranged from HR 1.11 (95% CI: 1.03-1.20) for postmenopausal breast cancer to HR 1.51 (95% CI: 1.27-1.80) for melanoma. Our study provides strong support for a positive association of adult height with risk of certain cancers. The underlying biological mechanisms are not clear but may differ by anatomic site.