Taller people may be at increased risk for some cancers, a British study of a million women suggests.
For every 10 centimeters, or four inches, in height above five feet, risk of cancer increased by 1.16 times, researchers found.
The study looked at 1.3 million women in the United Kingdom who were enrolled between 1996 and 2001. During an average follow-up of 10 years, 97,000 cases of cancer were identified.
A total of 10 cancers were linked to height — colon, rectal, malignant melanoma, breast, endometrial, ovarian, kidney, lymphoma, non-Hodgkin lymphoma and leukemia.
One of the strongest associations was seen in colon cancer, where every 10-centimeter increase in height corresponded to a 1.25 times increase in cancer risk.
Jane Green from the University of Oxford and her co-authors also reviewed the results of 10 previous studies on height and cancer risk across populations in four continents.
"Of course people cannot change their height. 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," Greer said in a journal release.
The similarity of risks associated with height for different cancers and in different populations suggests that a basic common mechanism, possibly acting early in life, might be involved, the study's authors said in Thursday's issue of the journal Lancet Oncology.
Hormone levels, especially of growth factors such as insulin-like growth factors, both in childhood and adulthood, might make a difference, they speculated.
'Need not be alarmed'
It is also possible that height predicts some cancer risk because taller people have more cells that could mutate leading to malignancies, the researchers said.
"Tall people need not be alarmed by these results," Sara Hiom of Cancer Research UK said.
"Most people are not a lot taller, or shorter, than average, and their height will only have a small effect on their individual cancer risk."
The association held up even when other factors known to contribute to cancer risk, such as smoking, were ruled out. But the link between height and cancer risk was weaker for smoking-related cancers, the authors noted.
The possible mechanisms of how height may affect cancer risk are unclear, said Dr. Andrew Renehan of the University of Manchester.
"In the future, researchers need to explore the predictive capacities of direct measures of nutrition, psychosocial stress, and illness during childhood, rather than final adult height," Renehan said in a journal commentary.
"Assessing these cohorts will need new methods to tease out key factors that influence the subsequent development of height-related cancers."
The study was funded by Cancer Research UK and the UK Medical Research Council.