July 24, 2024
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We have a well justified interest and concern regarding the relationship between weight/obesity and cancer risk. But what about the other metric of our size, height? Does that play a role as well?

Height is discussed at length in a well-written chapter in one of the volumes written by Malcolm Gladwell. In it, he points out how much a person’s height influences our attitude towards him/her. Presidents of the United States and CEOs of large corporations almost uniformly share an increased height over their peers, as do most world leaders, Napoleon notwithstanding. There is a fascinating series of letters by John Adams in which he (jealously?) claims that George Washington’s main attribute that qualified him for the presidency (over the short Adams) was his tall stature. And we need go no further than the first Book of Samuel (Samuel I 10:23-24) to see that the choice of Saul as the first king of Israel was no less influenced by his height.

A person’s height is certainly a product of his genes—no question about it. But nutrition and caloric intake play a significant role as well. The average height in many countries has been increasing steadily over the past century as nutrition and caloric intake have gradually improved.

So where does that leave us with the relationship between height and cancer? The answer is that most studies have shown a fairly consistent association between increasing height and increasing cancer risk. This increasing association has not been relegated to any specific cancer but has been seen consistently across most cancer sites.

An excellent study of this phenomenon was published in 2019 by Choi et al in the British Journal of Cancer. They looked at 23 million Koreans and explored the association of height and risk of cancer. They found almost linear associations between height and cancers of the nervous system, thyroid, prostate, breast, lung, colon, rectum, ovary, testes, cervix, endometrium, skin, lymphoma, multiple myeloma, leukemia, oral cavity, urinary bladder, pancreas, liver and stomach. Importantly, this study was not an outlier—it was consistent with multiple prior studies reported from Western populations.

So now let us ask, “What is it that height represents, or what exactly is the causal mechanism at play?” When something impacts on so many cancer sites, it must truly have some profound universal effect. What can it be?

Two hypotheses have been suggested for these observations. The first is the impact of insulin-like growth factor 1 (IGF1), a hormone that is similar to insulin and plays an important role in childhood growth. It has been found to be elevated in association with multiple cancers. Many scientists believe that this could indeed be part of the story, albeit an indirect one.

A more direct explanation would originate from the idea that increased height is associated with increased organ size, and larger organs have more cells which increases the probability that a mutation may occur. This may seem simplistic but, in essence, more cells in taller people provide a greater opportunity for carcinogenesis to occur.

The idea that more cells lead to more cancers has a precedent in breast cancer as well. It is well recognized that breast cancer is more frequent in the left breast than in the right breast. While the ratio of left to right may vary by country and ethnicity, a good estimate is 55% versus 45% for left versus right breast cancer in the U.S. Various reasons for this disproportionality have been proposed but perhaps the simplest is that in most women the left breast is larger than the right breast, hence leading to more cancers on that side.

Since we have started on this path, we may as well take it to its logical conclusion, i.e., why is the left breast larger than the right breast? For this question, we resort to anatomy and the fact that the outlet of blood flow from the heart points to the left (blood from the heart emanates from the left ventricle), leading to increased blood flow to that side of the chest/body and thus greater opportunity for cellular growth and development. This has other ramifications besides the laterality of breast cancer. Increased blood flow to the left side of the body also leads to increased blood flow to the left side of the brain as compared to the right side of the brain. Thus, in most people, the left side of the brain is more developed and, because of the crossing of our neurologic wiring (the left side of our brain controls the right side of our body and vice versa) we end up with 85% of the population being right-dominant.

At least some of these same mechanisms that relate height to cancer risk may also play a role in obesity and cancer risk. But obesity seems to be a more complex variable.


Alfred I. Neugut, MD, PhD, is a medical oncologist and cancer epidemiologist at Columbia University Irving Medical Center/New York Presbyterian and Mailman School of Public Health in New York.

This article is for educational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment, and does not constitute medical or other professional advice. Always seek the advice of your qualified health provider with any questions you may have regarding a medical condition or treatment.

 

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