HEIGHT INCREASES CANCER RISK?

Yet another study has found a link between height and the risk for cancer.

In a large prospective cohort of postmenopausal women, researchers found a modest but statistically significant positive association between height and risk for any cancer and risk for melanoma, multiple myeloma, and cancers of the thyroid, ovary, colorectum, and endometrium.

These associations were not explained by other known risk factors, including cancer screening, according to a reportpublished online July 25 in Cancer Epidemiology, Biomarkers & Prevention.

The positive association between height and cancer has also been seen in men in "several studies," study chief Geoffrey Kabat, PhD, senior epidemiologist in the Department of Epidemiology and Population Health at Albert Einstein College of Medicine of Yeshiva University in New York City, told Medscape Medical News.

An Independent Risk Factor

Dr. Kabat's team examined the association between height and risk for all cancers combined and for cancer at 19 specific sites in 144,701 women measured at enrollment in the Women's Health Initiative. During a median follow-up of 12 years, 20,928 women incident cancers were identified.

For every 10 cm increase in height, there was a 13% increase in risk of developing any cancer, after adjustment for "all important potential confounders," including age, weight, education, smoking habits, alcohol consumption, and hormone therapy, the researchers report.

There was also a 13% to 17% increase in the risk for melanoma and for cancers of the breast, ovary, endometrium and colon, and a 23% to 29% increase in the risk for cancers of the kidney, rectum, thyroid, and blood.

None of the 19 cancer sites showed a significant inverse association with height.

Table. Hazard Ratio for the 19 Cancer Sites Studied

Cancer	Hazard Ratio	95% Confidence Interval
Any	1.13	1.11–1.16
Cervix	1.38	0.96–1.99
Multiple myeloma	1.29	1.06–1.57
Thyroid	1.29	1.05–1.58
Brain	1.26	0.99–1.62
Rectum	1.25	1.02–1.53
Kidney	1.23	1.05–1.43
Colorectum	1.17	1.09–1.26
Endometrium	1.16	1.07–1.26
Colon	1.16	1.07–1.26
Melanoma	1.15	1.04–1.26
Ovary	1.13	1.00–1.29
Breast	1.13	1.08–1.17
Lung (never smoker)	1.12	0.92–1.38
Non-Hodgkin's lymphoma	1.11	0.99–1.23
Lung (ever smoker)	1.09	1.00–1.19
Bladder	1.06	0.90–1.24
Stomach	1.05	0.82–1.35
Leukemia	1.05	0.90–1.22
Pancreas	1.03	0.89–1.20

The researchers considered the possibility that cancer screening might be a confounder of the association between height and cancer. It wasn't. The association remained after the model mammography, Pap, and colorectal cancer screening histories were included.

"The study seems to confirm previous findings and add to the growing body of evidence that suggests that height is positively associated with total cancer risk and with risk for certain cancer types," Roland B. Walter, MD, PhD, from the Fred Hutchinson Cancer Research Center in Seattle, toldMedscape Medical News.

Dr. Walter wasn't involved in this study. However, in the recent Vitamins and Lifestyle (VITAL) study, he and his colleagues found evidence that height differences might be one factor affecting the excess cancer risk seen in men (J Natl Cancer Inst. 2013;105:860-868).

In the VITAL study of 65,308 adults 50 to 76 years of age, 3466 cancers of shared anatomic sites were identified. The researchers found that men had a 55% increased risk for cancer at shared sites (hazard ratio, 1.55; 95% confidence interval [CI], 1.45 - 1.66). When they accounted for height, 33.8% of the excess risk for men was explained by the height differences between sexes (95% CI, 10.2% - 57.3%).

Other large cohort studies have also shown ties between height and cancer. For example, in the Million Women Study, taller women had an increased risk of developing several types of cancer, as reportedby Medscape Medical News. For a woman of any height, the risk for cancer was 16% greater than for a woman 10 cm shorter. A meta-analysis that combined these results with those from 10 published prospective studies yielded similar findings.

And, in a previous study, Dr. Kabat's team found similar ties between cancer and increasing height in a cohort of Canadian women (Int J Cancer. 2013;132:1125-1132).

What might be behind this association? "One possibility is that improved nutrition in childhood — greater intake of calorie-dense foods and of milk — is associated with increased circulating levels of the hormone insulin-like growth factor-1 [IGF-1] and with increased linear growth and greater height," Dr. Kabat said. "IGF-1 promotes cell proliferation — a process that contributes to cancer. This is perhaps the most plausible explanation at this time," although there are others that need to be considered, he added.

In fact, genome-wide association studies have identified at least 180 single nucleotide polymorphisms (SNPs) associated with height in humans. The association between height and cancer risk "might be explained if SNPs associated with height, or SNPs in linkage disequilibrium with these SNPs, are deemed functional and predispose men and women to cancer," Dr. Kabat and colleagues note.

Dr. Kabat and Dr. Walter have disclosed no relevant financial relationships.

Cancer Epidemiol Biomarkers Prev. Published online July 25, 2013. Abstract