Taller women at greater risk for cancer
Taller women are at greater overall risk for cancer than those who are shorter, data from a large prospective U.K. study indicate, but the degree of risk varies depending on the type of cancer.
Every four-inch increase in height over 5 feet, correlates with a 16% increase in cancer risk (5% CI: 1.14-1.17; P<0.0001), Jane Green, DPhil, of the University of Oxford, and colleagues wrote in Lancet Oncology.
Although previous smaller studies have reported associations between height and cancer risk, little is known about how factors such as cancer type, smoking and socioeconomic status influence risk.
To determine this, the researchers analyzed data from 1.3 million women who participated in the Million Women Study between 1996 and 2001. Participants had a mean age of 53 years and a mean height of 5 feet 3 inches. A total of 97,376 new cases of cancer were identified in the 11.7 million person-year follow-up period.
Height mediated cancer risk to greater or lesser degrees depending on the type of cancer, the researchers found – with the greatest relative risks per four-inch height increase occurring with malignant melanoma (RR=1.32; 95% CI: 1.24-1.40), kidney cancer (RR=1.29; 95% CI: 1.19-1.41) and leukemia (RR= 1.26; 95% CI: 1.15-1.38).
Other cancers for which the researchers observed statistically significant increases in risk per four-inch height increase include:
- Colon (RR=1.25; 95% CI: 1.19-1.30)
- Rectum (RR=1.14; 95% CI: 1.07-1.22)
- Breast (RR=1.17 (95% CI: 1.15-1.19)
- Endometrium (RR=1.19; 95% CI: 1.13-1.24)
- Ovarian (RR=1.17; 95% CI: 1.11-1.23)
- Central nervous system (RR=1.20; 95% CI: 1.12-1.29)
- Non-Hodgkin Lymphoma (RR=1.2; 95% CI: 1.14-1.29)
The association between greater height and increased total cancer risk was similar across many different populations, including people from Asia, Australasia, Europe and North America.
“The link between height and cancer risk seems to be common to many different types of cancer and in different people; suggesting that there may be a basic common mechanism, perhaps acting early in peoples' lives, when they are growing,” Green said in a press release.
The researchers also analyzed at how personal factors including socioeconomic status, age at menarche and at birth of the first child, smoking, physical activity, and use of oral contraceptives influenced height-related cancer risk.
They found that only smoking status influenced the findings – with current smokers at lower risk for cancer with each four-inch height increase than their counterparts who had never smoked (P<0.0001).
To determine whether gender plays a role, the researchers combined findings from the Million Women Study with data from an additional 10 prospective studies that evaluated the influence of height on cancer risk in both men and women.
Results of this meta-analysis indicated that although the correlation remained between each four-inch increase in height and cancer risk, it was slightly lower among men (RR= 1.10 vs. 1.15; P<0.0001).
The differences in relative risk observed in men and women may be attributable to the fact that fewer women were current smokers than men, the researchers hypothesized.
Although it is not clear exactly how height and cancer risk are related, the researchers suggested that factors including genetics, nutrition and hormones, including insulin-like growth factors might play a role.
“Of course people cannot change their height,” Green said. “Being taller has been linked to a lower risk of other conditions, such as heart disease. The importance of our findings is that they may help us to understand how cancers develop.”
In an accompanying editorial, Andrew G. Renehan, PhD, of the University of Manchester in England, called for more studies with “new methods to tease out key factors that influence the subsequent development of height-related cancers.”
These should “explore the predictive capacities of direct measure of nutrition, psychosocial stress and illness during childhood, rather than final adult height,” he wrote.