British investigators are reporting that taller women have a higher risk of cancer, and that the link between height and cancer risk exists for most types of cancer. In fact, the results of this large, prospective study showed "a clear and highly significant trend" of increasing cancer risk with increasing height in UK women, with a 16% hike in cancer risk for every 10 cm (or 4 inches) increase in height.
Jane Green, MD, with the University of Oxford in England, and colleagues examined the association between height, other factors relevant for cancer, and cancer incidence in 1,297,124 women aged ≥50 years who were recruited for the Million Women Study between 1996 and 2001. The Million Women Study is exploring how various reproductive and lifestyle factors affect women's health, with a strong focus on a wide range of cancers and other conditions, such as fractures, gallbladder disease, and cardiovascular disease.
While epidemiologic studies had shown that taller people are at increased risk of cancer, the researchers said it had not been known whether or not heightassociated risk differs among cancer sites and as a function of such variables as cigarette smoking and socioeconomic status.
During the median follow-up period of 9.4 years, a total of 97,376 cases of cancer were identified.
The relative risk (RR) of total cancer was 1.16 (95% confidence interval [CI], 1.14-1.17; P
<.0001) for every 10-cm increase in height.
In addition, the RR of cancer was increased for 15 of the 17 cancer sites that were assessed and was significant for 10 sites, including colon, rectum, malignant melanoma, breast, endometrium, ovary, kidney, central nervous system, non-Hodgkin lymphoma, and leukemia.
The height-associated RR of cancer was lower for smoking-related cancers than for other cancers but only in current smokers.
Green and associates also conducted a meta-analysis of published results from prospective studies on the association between height and total cancer incidence on mortality. Results were highly consistent for incidence and mortality and in populations from Europe, North America, Asia, and Australasia, thereby suggesting that "a basic common mechanism, possibly acting early in life, may be involved," they said.
They pointed out that while it is not yet known how height is linked to an increased cancer risk, height is determined by environmental factors including diet and infections in childhood, as well as growth hormone levels and genetic factors. It is possible that height predicts cancer risk because taller people have more cells (including stem cells), and thus have more opportunities for mutations that may produce malignant transformation.
Finally, the researchers said their observations suggested that increases in the height of populations over the 20th century may have contributed to some of the changes in cancer incidence over time. Specifically, European adults grew by about 1 cm per decade throughout the 20th century; this may account for the increase in cancer incidence, which was 10% to 15% higher than expected had population height been constant.
Green J, Cairns BJ, Casabonne D, et al. Height and cancer incidence in the Million Women Study: prospective cohort, and meta-analysis of prospective studies of height and total cancer risk. Lancet Oncol. 2011;12(8):785-794. doi:10.1016/S1470- 2045(11)70154-1.