Taller people have a higher risk of developing some types of cancer — including lymphoma — because they have a larger number of cells, according to a University of California, Riverside study.
The study, “Size matters: height, cell number and a person’s risk of cancer,” was published in the journal Proceedings of the Royal Society B.
Most cancers occur because, over time, cells lose regulatory genetic mechanisms and accumulate harmful mutations. More cells means more mutations, leading researchers to believe that a higher number of cells might be associated with an increased likelihood of developing cancer.
In humans, the risk of cancer tends to increase with age. There also is some evidence suggesting that taller people — who have a greater number of cells — have an increased risk of developing cancer.
However, few studies have addressed this issue, primarily because height does not vary greatly in humans and large datasets are needed to evaluate height independently from other cancer risk factors — including another measure of body mass, obesity.
A team of researchers at the University of California designed a model that is able to predict the increased risk of developing certain cancers related to a height increase of 10 centimeters (almost four inches).
Using the model, they expected to prove whether an increase in cell number, instead of indirect factors related to height, increased the risk of developing certain cancers.
They evaluated data collected in studies from the U.S., U.K., Norway, Korea, Austria, and Sweden.
Among the 23 cancers studied, height was deemed a risk factor for 18 of them. In men, height correlated with the risk for cancers of the skin, thyroid, colon, lymph nodes, biliary tract, and central nervous. In women, the risk for skin, thyroid, colon, womb, breast, ovarian cancers, and lymphoma all increased with height.
Overall, for each 10 centimeters of increased height, the model predicted that cancer risk increased by 13% in women and 11% in men. These predictions matched real-life data — even after accounting for confounding effects of age, body mass index, smoking status, and menopausal status — in which women had a 12% higher risk for cancer with a 10 centimeter increase in height, and men saw their risk increase by 9%.
The fact that the data fit so well with the model “indicates that the increased cancer risk associated with height is due primarily to an increase in cell number,” researchers commented.
They also noticed that the environment highly influenced some of the cancers that were not affected by differences in height. For example, lung cancer and smoking, and cervical cancer and HPV infection.
The scores for skin cancer, specifically melanoma, were too high to be related solely to an increase in the number of cells. “One possible secondary effect implicated in the case of melanoma is an increased rate of cell division during adult life,” researchers observed.
Men have a higher risk of developing cancer than women, possibly because they tend to be taller than women. However, height and cell numbers “can only account for about one-third of the increased male cancer risk,” suggesting that other factors are in play.
Overall, this model offers a simple explanation as to why increased height also might increase the overall risk of cancer.