Hormones Responsible For Some Men’s Long Legs May Up Their Colorectal Cancer Risk

long legs
Men with longer legs have a 42 percent higher risk of developing colorectal cancer than those with shorter legs. Dan Kitwood, Getty Images

Your risk of developing cancer depends in part on your height, past research suggests, with taller people being more prone to the disease than their shorter friends. Scientists hypothesize this could be due to either their generally higher intake of calories, the larger number of cells in their bodies (raising the odds of some cells transforming into cancer), or exposure while young to higher levels of growth factor hormones. A new study makes similar, though slightly more nuanced, claims.

The researchers say men with longer legs have a 42 percent higher risk of developing colorectal cancer than those with shorter legs.

The dramatic findings indicate men with the longest legs (35.4 inches on average) have a 91 percent greater risk of colon cancer than men with the shortest legs (31.1 inches on average). Leg length differences in women, however, appear to have no bearing on cancer risk, with comparisons between the tallest and shortest legs leading to statistically insignificant differences in cancer risk.

Led by Guillaume Onyeaghala, a graduate student at the University of Minnesota, a team of researchers compared leg length, sitting height (seat to top of the head), and total height with colorectal cancer risk. For data, they turned to the Atherosclerosis Risk in Communities (ARIC) study, whose participants included 14,605 men and women. Tracked through the year 2006, the participants began the study during the late 1980s when they were all cancer-free.

For the current study, Onyeaghala and his colleagues focused on estimates of leg length (standing height minus sitting height) and compared these calculations to colorectal cancer incidence among the group. During the course of ARIC, 344 people received a diagnosis of this cancer, which affects the colon or rectum. Following statistical analysis based on quartiles of height and leg length, among other factors, the researchers adjusted their model for various demographic factors as well as hormone replacement therapy use and smoking status.

Crunching the numbers, they discovered male participants in the highest quartile of leg length were at a 42 percent greater risk of colorectal cancer compared to the lowest quartile, though this did not hold for women. The highest quartiles of total height and sitting height also showed a greater risk of cancer when compared to the lowest quartiles, but here it was a much weaker association, the researchers noted.

Though they say the association could be due to taller people having a larger pool of colonic cells (and therefore higher odds of some turning malignant), they believe it is more likely driven by greater exposure during puberty to insulin-like growth factor-1. Similar in molecular structure to insulin and primarily produced by the liver, this hormone regulates bone length development. National Cancer Institute research has linked higher levels of this natural hormone to colorectal cancer in both men and women, while a Harvard study found higher-than-usual levels associated with a significantly increased risk of colorectal, breast, and prostate cancers.

Source: Onyeaghala GC, Lutsey PL, Demerath EW, et al. Associations of leg length with increased colorectal cancer incidence in the atherosclerosis risk in communities (ARIC) study. AACR Annual Meeting. 2016.

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