Cancer risk increases with height, suggest researchers from Karolinska Institutet and University of Stockholm in Sweden.

“In our preliminary report, we present that for every 10-centimeter [about 4 inches] increase in height, overall cancer is increased by 18 percent in women and 11 percent in men,” said the researchers in a statement accompanying their presentation at the European Society for Pediatric Endocrinology.

Past studies have shown that taller people have a higher risk of developing different types of cancer, including breast cancer and melanoma, say the researchers. To investigate, a team led by Emelie Benyi, a Ph.D. student at Karolinska, examined medical and other records and tracked a large group of people — a total of 5.5 million men and women, all born in Sweden between 1938 and 1991, ranging in height (as adults) from 100 cm (3-foot-3) to 225 cm (7-foot-3). The team derived information from various databases, including the Swedish Medical Birth, the Swedish Conscription, the Swedish Passport Registers, and the Swedish Cancer Register. Tracking the group until the end of 2011, the researchers came to some surprising results.

“We found that total cancer risk and risks of breast cancer and melanoma were higher with increasing height in the Swedish population,” wrote the authors.

With each 10 cm of height, cancer risk increased by 18 percent in women and 11 percent in men, the researchers say. For both men and women, the risk of developing melanoma increased by nearly 30 percent per 10 cm, while taller women had a 20 percent greater risk of developing breast cancer.

One Example & Three Possible Reasons

Confused by all these percentages? The researchers say their risk estimates are comparisons, not absolute risks, and give this example to explain how it works: Swedish women have a 10 percent risk of developing breast cancer in their lifetimes. This scientific esimate was calculated based on a woman's height of 170 cm.

“According to our data where breast cancer is increased by 20 percent for each 10 cm increase in height, women of a height of 160 cm would in this example instead have a life time risk of breast cancer of about 8  percent and women of 180 cm would have a life time risk of about 12 percent,” the researchers wrote.

Benyi and her colleagues emphasized their results are only preliminary and only apply to Sweden. Having controlled for education and income, they explained socioeconomic variables did not change the results in any significant way.  

So how about answering the key question — why is height linked to cancer? Possibly, the team explained, taller people (while young) are exposed to higher levels of growth factors, which could possibly promote cancer development. This, though, has not been verified.

“Another hypothesis could be that taller people simply have a larger number of cells in their bodies that then could potentially transform into cancer,” they wrote. “A third possible explanation is that taller individuals have a higher caloric intake, which has also previously been linked to cancer.”

Source: Benyi E, Linder M, Adami J, et al. Positive association between height and cancer in the Swedish population. European Society for Paediatric Endocrinology. 2015.