Tall people at greater risk of cancer?

While for most cancers, risk increases dramatically with age, a recent study has found that the height of a person could also make them more prone to cancer.

The University of California study has been published in the journal Proceedings of the Royal Society B.

Leonard Nunney examined data from four large-scale surveillance projects on 23 cancer categories. Each of these cancer studies established that tall individuals are at an increased risk of cancer, with overall risk increasing by about 10 percent per 10 centimeter (4 inch) increase in height.

Other researchers have proposed that that factors acting early in life - nutrition, health, social conditions - independently influence height and cancer risk. But Nunney, a professor of biology, challenges this hypothesis.

 

"I tested the alternative hypothesis that height increases cell number and that having more cells directly increases cancer risk," he said. "The data strongly supported this simple hypothesis. For most cancers, the size of the height effect is predictable from the height-related increase in cell number."

When Nunney performed a comparison of the observed effect of height on the risk of specific cancers for both women and men, he found that the effect of being tall on the risk of thyroid and skin cancer was high in women; for men, skin cancer stood out.

"Tall individuals are at increased risk of almost all cancers," he said. "But skin cancers - such as melanoma - show an unexpectedly strong relationship to height. This may be because the hormone IGF-1 is at higher levels in taller adults."

IGF-1 is a growth factor that is particularly important in early development, Nunney explained, but IGF-1 has also been linked to a higher rate of cell division in tall adults.

"If your cells divide more often, then that adds to your cancer risk," he said. "If skin cells are dividing more rapidly in tall people due to high levels of IGF-1, then this could account for the increased risk for melanoma.