NEW ORLEANS — Colorectal cancer has been linked to a number of risk factors, such as inactivity, smoking and eating a lot of red meat. Now, a new study suggests a slightly more surprising risk factor: long legs.
Compared with people who had shorter legs, those with longer legs had a 42 percent higher risk of developing colorectal cancer, according to the new study presented here today (April 19) at the American Association for Cancer Research's annual meeting.
Evidence from previous studies has suggested that taller people in general are more likely to develop colorectal cancer, said Guillaume Onyeaghala, a graduate student in epidemiology at the University of Minnesota and the lead author of the study.
Researchers have two hypotheses that may explain the association between height and cancer risk, Onyeaghala told Live Science. [Top 10 Cancer-Fighting Foods]
One idea is that because taller people have longer colons (and therefore, more surface area within the organs where colon cancer could develop), they have more chances to develop the condition, Onyeaghala said. The other suggestion is that increased levels of growth hormones — which affect leg length in particular — are also the driving factor for colorectal cancer, he said. (The growth hormone "insulin-like growth factor 1" is elevated during puberty, and has been shown to be a risk factor for colorectal cancers at high levels, the study said.)
The researchers looked at data on participants in the Atherosclerosis Risk in Communities Study, a long-running cohort of more than 14,500 men and women. Specifically, the new study examined three aspects of the participants' height: overall height, torso height and leg length. Researchers also looked at how many participants developed colorectal cancer over the nearly 20-year study period.
The only factor that was linked to people's colon cancer risk was their leg length; the researchers did not find a significant link between people's overall height or torso height and their cancer risk, Onyeaghala said. [10 Do's and Don'ts to Reduce Your Risk of Cancer]
Because sex is related to height, the researchers also looked at men and women separately. Results showed that in men, those with the longest legs (an average length of 35.4 inches, or 90 centimeters) had a 91 percent greater risk than those with the shortest legs (an average length of 31.1 inches, or 79 cm), Onyeaghala said. In women, there were no statistically significant differences in risk.
Because leg length was more strongly associated with colorectal cancer risk than were sitting height or overall height, these results support the hypothesis that the growth factors that drive bone growth in the legs are a risk factor for the disease, Onyeaghala said. (However, the idea that a longer colon is to blame cannot be ruled out based on these results.)
The findings have not been published in a peer-reviewed journal.