Posted: Jul 20, 2011 11:25 PM
July 20, 2011 -- Taller women are at greater risk for many types of cancers compared with shorter women, a new study suggests.
In the study, cancer risk rose by about 16% for every 4-inch increase in height. The risk of total cancer increased with height, as did the risk of many different types of cancer including breast, ovary, uterine, and colon cancer as well as leukemia and melanoma, a potentially fatal form of skin cancer.
The findings appear online in the Lancet Oncology.
Several studies have linked height to cancer risk, but the precise nature of the relationship is still poorly understood. "Growth hormones are one theory [as] they have been linked to both height and cancer risk in childhood or in adult life, or tall people may simply have a greater chance of cancerous cell changes, because they have more cells," says study researcher Jane Green of the Cancer Epidemiology Unit at the University of Oxford, U.K., in an email.
Green and colleagues looked at the relationship between height and cancer among 1.3 million middle-aged women who were enrolled between 1996 and 2001. During an average follow-up of 10 years, there were 97,376 cases of cancer.
Women were grouped into six categories based on their height when they were recruited into the study. The tallest women were about 5 feet 10 inches or taller and the shortest women in the study measured about 5 feet 1 inch or less. There were about 8 and 1/4 inches between the tallest and shortest women in the study; the average height was between 5 feet 3 inches and 5 feet 4 inches.
Taller women were at higher risk for all cancers, and this increased risk was seen regardless of the year they were born, socioeconomic status, body mass index, alcohol intake, physical activity, age when they began menstruating, use of oral contraceptive and hormone replacement therapy, and other factors that are known to affect cancer risk.
The increased risk associated with height was lower for smoking-related cancers among current smokers, the study showed.
The researchers also combined their results with those from 10 previous studies to show that the findings also hold across Europe, North America, Australia, and Asia.
"The importance of this research is in understanding how cancers develop," Green says. "Because height is linked to a wide range of cancers in a wide range of people, it may give us a clue to a basic common mechanism for cancer."
Going forward, "it will be interesting to look in more detail at possible mechanisms, and at the relationship between cancer risk and more detailed aspects of height and growth in childhood," she says.
"Taller people in general are healthier and have lower risk of heart disease, and most people are not very much taller or shorter than average, so their cancer risk is not much different from the average risks usually quoted," she says.
"This very large and well-designed study including over a million women shows somewhat higher risk of many cancers, and cancer overall, with increasing height," says Eric Jacobs, PhD, strategic director of pharmacoepidemiology at the American Cancer Society, in an email.
The underlying biological reason for the slightly higher risk among taller people is not known, he says.
"One possibility is that taller people may have higher levels of growth-related hormones, both in childhood and in adulthood, and these growth-related hormones may modestly increase cancer risk," he says. "Interestingly, height had relatively little relationship to risk of smoking-related cancers among smokers, highlighting the overwhelming importance of smoking."
"Nobody will be trying to make themselves shorter to lower their cancer risk. And the current results do not mean tall people need additional cancer screening," Jacobs says. "The bottom line is that both short and tall people can lower their risk of developing and dying from cancer by not smoking, maintaining a healthy weight, and getting the recommended cancer screening tests."
According to Walter Willet, MD, MPH, chair of the department of nutrition and the Fredrick John Stare professor of epidemiology and nutrition at the Harvard School of Public Health in Boston, "this analysis confirms the relation between height and risks of many cancers and this information does point us to new lines of research, especially factors in childhood that influence height and how they're related to cancer risk."