"These are modestly increased risks," says study author Dr. J. Michael Gaziano, chief of the division on aging at Brigham and Women's Hospital, an affiliate of Harvard Medical School in Boston.
Using data from the Physicians Health study of 22,071 men in the United States, the researchers zeroed in on 1,634 men with prostate cancer, asking about their age, height, weight and body mass index (BMI), a ratio of height to weight.
They evaluated three categories of height: less than 5 feet 10 inches; 5-foot-10 to 5-foot-11; and over 5-foot-11.
Among the men who were 50 to 59 years old, those 5-foot-10 to 5-foot-11 had a 21 percent greater risk of prostate cancer than those under 5-foot-10. Those over 5-foot-11 had a 32 percent greater risk.
For men who were 60 to 84, those who were 5-foot-10 to 5-foot-11 had a 22 percent higher risk than shorter men in the same age bracket, while those above 5-foot-11 had a 24 percent higher risk..
Exactly why is not known, Gaziano says: "We've seen an association with shorter people having an increased risk for cardiovascular events, and we don't know why [that happens] either."
"Height might just be a genetic marker for some other genetic reason you might be at risk," he speculates.
The study is not the first to link taller height with prostate cancer, Gaziano says. Other researchers have studied the association, with mixed findings. "The data in general [on the topic] are very limited, and this needs to be explored and then duplicated or refuted before we can say something definite," he says.
The researchers did not find an association between weight or BMI with prostate cancer.
This year, about 220,900 new cases of prostate cancer will be diagnosed in the United States, according to the American Cancer Society. Early prostate cancer usually has no symptoms; risk factors include increasing age, ethnicity and family history. More than 70 percent of all prostate cancers are found in men who are over age 65. Black men have the highest prostate cancer rates in the world.
An annual digital rectal exam and a PSA blood test to detect levels of prostate specific antigen are recommended by the American Cancer Society for all men beginning at age 50; for those at elevated risk, the recommended age for the tests is 45.
Another expert, Dr. Allan Pantuck, notes previous studies have yielded conflicting findings about prostate cancer risk and height, weight and BMI. "Most show an association with obesity," he says.
Also, the latest study is an observational one and does not prove a cause-and-effect relationship, adds Pantuck, who is an assistant professor of urology at the University of California, Los Angeles, Jonsson Cancer Center.
What's the take-home point for tall guys?
"Obviously men can't change their height, and we already know men over age 50 are the group for whom we recommend prostate cancer screening," Pantuck says.
Gaziano agrees, but stresses that men should continue to observe the recommendations for screening. Eventually, if more research bears out the association between height and prostate cancer, it will help researchers and physicians better zero in on the men most likely to contract the disease, he says.
Dr. Noriko Kojimahara of Japan, who conducted the research while at Harvard, will present the study's findings Feb. 20 at the American College of Preventive Medicine meeting in San Diego.