More than one-third of the excess risk for cancers among men may be due to factors associated with height, according to data from the Vitamins and Lifestyle (VITAL) study. As reported in the Journal of the National Cancer Institute, these factors include the “number of susceptible cells in a specific organ or growth-influencing exposures in childhood.”
Using the Surveillance, Epidemiology, and End Results (SEER) cancer registry, a total of 3,466 cancers of anatomic sites that men and women have in common were identified among 65,308 VITAL volunteers aged 50 to 76 years. The mean height for men was 70.67 inches vs 64.67 inches for women. Men were also heavier than women, exercised more, consumed more alcohol and red meat and fewer servings of fruits and vegetables, smoked more in their lifetime, and were more educated.
“Men had a 55% increased risk of cancer at shared sites (HR = 1.55; 95% confidence interval [CI] = 1.45 to 1.66),” the researchers reported. “When height was accounted for, 33.8% (95% CI = 10.2% to 57.3%) of the excess risk for men was explained by the height differences between sexes. The proportion mediated by height was 90.9%, 57.3%, and 49.6% for kidney, melanoma, and hematologic malignancies, respectively, with little evidence that height mediates the sex difference for gastrointestinal tract, lung, and bladder cancers. For comparison, more than 35 lifestyle and medical risk factors only explained 23.1% of the sex difference in cancer risk at shared sites,” the researchers noted.
Observations that some cancers, such as thyroid and breast cancers, are less common among men and that height is associated with some cancers but not others “indicate there are multiple biologic and behavioral mechanisms that vary by anatomic site that may explain the sex differences in cancer risk,” the authors stated.
“One postulated mechanism related to height is that taller individuals may be at increased risk of cancer because of a larger number of cells and higher rate of cell divisions within tissues,” they continued. “Consistent with this hypothesis, for instance, a case–control study reported a strong association between melanoma risk and body surface area, as measure of skin cell mass at risk of malignant transformation. Proposed mechanisms contributing to the association between height and cancer risk, perhaps by influencing the number of proliferating cells and/or other pathways, include genetic factors, energy intake in early life, and exposure to sex and growth hormones.” ■
Walter RB, et al: J Natl Cancer Inst 105:860–868, 2013.