BALTIMORE — Tall individuals may want to screen for colorectal cancer more often than their vertically challenged peers, according to new research from Johns Hopkins Medicine. Scientists report tall adults might have a greater risk of developing colorectal cancer or malignant colon polyps.
While this isn’t the first research project to investigate the link between height and colorectal cancer risk, the study authors explain those prior initiatives yielded conflicting results, employed inconsistent height measurements, and failed to account for adenoma risk. Adenomas are precancerous colon polyps.
“This is the largest study of its kind to date. It builds on evidence that taller height is an overlooked risk factor, and should be considered when evaluating and recommending patients for colorectal cancer screenings,” says Dr. Gerard Mullin, associate professor in the Division of Gastroenterology and Hepatology at Johns Hopkins Medicine, in a press release.
‘Tallest individuals had 24% higher risk’
To be clear, researchers caution that this work does not definitely prove a causal effect. Similarly, it is uncertain whether being tall is as dominant a risk factor for cancer as age or genetics. However, the current findings strengthen long-observed associations between a taller stature and higher colorectal cancer risk.
“One possible reason for this link is that adult height correlates with body organ size. More active proliferation in organs of taller people could increase the possibility of mutations leading to malignant transformation,” adds co-first study author Dr. Elinor Zhou.
The team reviewed 47 international studies covering 280,660 colorectal cancer cases and 14,139 cases of colorectal adenoma. They also included data from a study featuring 1,459 adult patients undergoing outpatient colonoscopies to better understand the relationship between cancer and bacteria stuck to colon walls.
One big consideration study authors kept in mind is the definition of “tallness.” Depending on country and nationality, the term can mean different things for different people. To tackle this aspect of the calculations, the team made comparisons among the highest versus the lowest height percentiles of many study groups.
“The findings suggest that, overall, the tallest individuals within the highest percentile of height had a 24% higher risk of developing colorectal cancer than the shortest within the lowest percentile. Every 10-centimeter increase (about 4 inches) in height was found to be associated with a 14% increased risk of developing colorectal cancer and 6% increased odds of having adenomas,” Dr. Mullin explains.
How tall is too tall?
The Centers for Disease Control & Prevention (CDC) says the average height of a male American adult is 5 feet, 9 inches, and 5 feet, 4 inches for women. According to these calculations, American men who are 6 feet, 1 inch tall and women who measure at 5 feet, 8 inches (4 inches higher than average U.S. height) or taller have a 14% increased risk of colorectal cancer and a 6% percent further risk of adenomas.
They adjusted percentage results based on demographic, socioeconomic, behavioral, and other known risk factors linked to colorectal cancer. Risk factors with “non-modifiable” elements include age, a personal or family history of colorectal cancer or adenomas, and a personal history of chronic inflammatory bowel disease. In the United States, doctors associate over half of colorectal cancer cases with various modifiable lifestyle factors, such as poor diet, neglecting exercise, a smoking habit, and excessive alcohol consumption.
While these risk factors are not directly comparable to tallness, the study authors stand by their thesis that tallness may provide a degree of elevated colorectal cancer risk similar to modifiable risk factors like cigarette smoking, moderate alcohol consumption, and eating lots of red meat. Today, most gastroenterologists focus entirely on genetics and age-related considerations to decide on whether their patient gets a colorectal cancer screening.
Colorectal cancer diagnoses are rising in young adults
Per the American Cancer Society, colorectal cancer is the third most common cancer in both men and women. Older adult colorectal cancer diagnoses have gradually declined in recent years. However, deaths linked to colorectal cancer among individuals younger than 50 have increased by 2% annually between 2007 and 2016. The reasons for this uptick remain unknown.
“Greater awareness by the public and government will help promote more interest and funding for more research, which ultimately could change guidelines for physicians to consider height as a risk for cancer,” Dr. Mullin notes. “There are well-known modifiable dietary associations for colorectal cancer, such as processed red meats and smoking, but guidelines currently are fixated on family history, and height is clinically neglected when it comes to risk screening.”
Future research should focus on which tall adult populations are at an increased risk for colon cancer. “For instance, tall athletes and individuals with inherited tallness, such as those with Marfan syndrome, could be screened earlier and the impact of height further explored,” Dr. Zhou concludes. “We need more studies before we can definitively say at what height you would need earlier colorectal cancer screening.”
The study is available to read in the journal Cancer Epidemiology Biomarkers & Prevention.