A person’s ‘genetic’ height – the height they are predicted to reach independent of environmental influences – may be an underappreciated risk factor for a wide range of chronic conditions, according to a study published in PLOS Genetics.
Prior studies have investigated height as a risk factor for chronic diseases, such as a higher risk for atrial fibrillation and a reduced risk of cardiovascular disease. It’s been consistently difficult, however, to eliminate the confounding influences of diet, socioeconomics, lifestyle behaviors, and other environmental factors that may interfere with a person’s reaching their expected height based on their genes.
This study, however, was able to better parse those differences by using Mendelian randomization within the comprehensive clinical and genetic dataset of a national health care system biobank. Mendelian randomization uses “genetic instruments for exposures of interest under the assumption that genotype is less susceptible to confounding than measured exposures,” the authors explained. The findings confirmed previously suspected associations between height and a range of cardiovascular and metabolic conditions as well as revealing new associations with several other conditions.
Prior Associations Confirmed, New Associations Uncovered
The results confirmed that being tall is linked to a higher risk of atrial fibrillation and varicose veins, and a lower risk of coronary heart disease, high blood pressure, and high cholesterol. The study also uncovered new associations between greater height and a higher risk of peripheral neuropathy, which is caused by damage to nerves on the extremities, as well as skin and bone infections, such as leg and foot ulcers.
The meta-analysis “identified five additional traits associated with genetically-predicted height,” wrote Sridharan Raghavan, MD, assistant professor of medicine at the University of Colorado Anschutz Medical Campus, and colleagues. “Two were genitourinary conditions – erectile dysfunction and urinary retention – that can be associated with neuropathy, and a third was a phecode for nonspecific skin disorders that may be related to skin infections – consistent with the race/ethnicity stratified results.”
Removing Potential Confounders
F. Perry Wilson, MD, associate professor of medicine at Yale University, New Haven, Conn., who was not involved in the study, said the findings were not particularly surprising overall, but it’s striking that the researchers had “such a large cohort with such detailed electronic health records allowing for the comparison of genetic height with a variety of clinical outcomes.” He also noted the study’s strength in using Mendelian randomization so that the exposure is the predicted genetic height instead of a person’s measured height.
“This is key, since lots of things affect actual height – nutrition is an important one that could certainly be linked to disease as well,” Wilson said. “By using genetic height, the authors remove these potential confounders. Since genetic height is “assigned” at birth (or conception), there is little opportunity for confounding. Of course, it is possible that some of the gene variants used to predict genetic height actually do something else, such as make you seek out less nutritious meals, but by and large this is how these types of studies need to be done.”
Height May Impact Over 100 Clinical Traits
The study relied on data from the U.S. Veteran Affairs Million Veteran Program with 222,300 non-Hispanic White and 58,151 non-Hispanic Black participants. The researchers first estimated the likelihood of participants’ genetic height based on 3,290 genetic variants determined to affect genetic height in a recent European-ancestry genome-wide meta-analysis. Then they compared these estimates with participants’ actual height in the VA medical record, adjusting for age, sex, and other genetic characteristics.
In doing so, the researchers found 345 clinical traits that were associated with the actual measured height in White participants plus another 17 clinical trials linked to actual measured height in Black participants. An overall 127 of these clinical traits were significantly associated with White participants’ genetically predicted height, and two of them were significantly associated with Black participants’ genetically predicted height.
In analyzing all these data together, the researchers were largely able to separate out those associations between genetically predicted height and certain health conditions from those associations between health conditions and a person’s actual measured height. They also determined that including body mass index as a covariate had little impact on the results. The researchers conducted the appropriate statistical correction to ensure the use of so many variables did not result in spurious statistical significance in some associations.
“Using genetic methods applied to the VA Million Veteran Program, we found evidence that adult height may impact over 100 clinical traits, including several conditions associated with poor outcomes and quality of life – peripheral neuropathy, lower extremity ulcers, and chronic venous insufficiency. We conclude that height may be an unrecognized nonmodifiable risk factor for several common conditions in adults.”
Height Linked With Health Conditions
Genetically predicted height predicted a reduced risk of hyperlipidemia and hypertension independent of coronary heart disease, the analysis revealed. Genetically predicted height was also linked to an approximately 51% increased risk of atrial fibrillation in participants without coronary heart disease but, paradoxically, only a 39% increased risk in those with coronary heart disease, despite coronary heart disease being a risk factor for atrial fibrillation. Genetically predicted height was also associated with a greater risk of varicose veins in the legs and deep vein thrombosis.
Another novel association uncovered by the analysis was between women’s genetically predicted height and both asthma and nonspecific peripheral nerve disorders. “Whether these associations reflect differences by sex in disease pathophysiology related to height may warrant exploration in a sample with better balance between men and women,” the authors wrote. “In sum, our results suggest that an individual’s height may warrant consideration as a nonmodifiable predictor for several common conditions, particularly those affecting peripheral/distal extremities that are most physically impacted by tall stature.”
A substantial limitation of the study was its homogeneity of participants, who were 92% male with an average height of 176 cm and an average BMI of 30.1. The Black participants tended to be younger, with an average age of 57 compared with 64 years in the White participants, but the groups were otherwise similar in height and weight. The database included data from Hispanic participants, but the researchers excluded these data because of the small sample size.
The smaller dataset for Black participants was a limitation as well as the fact that the genome-wide association study the researchers relied on came from a European population, which may not be as accurate in people with other ancestry, Wilson said. The bigger limitation, however, is what the findings’ clinical relevance is.
What Does It All Mean?
“Genetic height is in your genes – there is nothing to be done about it – so it is more of academic interest than clinical interest,” Wilson said. It’s not even clear whether incorporating a person’s height – actual or genetically predicted, if it could be easily determined for each person – into risk calculators. “To know whether it would be beneficial to use height (or genetic height) as a risk factor, you’d need to examine each condition of interest, adjusting for all known risk factors, to see if height improved the prediction,” Wilson said. “I suspect for most conditions, the well-known risk factors would swamp height. For example, high genetic height might truly increase risk for neuropathy. But diabetes might increase the risk so much more that height is not particularly relevant.”
On the other hand, the fact that height in general has any potential influence at all on disease risk may inspire physicians to consider other risk factors in especially tall individuals.
“Physicians may find it interesting that we have some confirmation that height does increase the risk of certain conditions,” Wilson said. “While this is unlikely to dramatically change practice, they may be a bit more diligent in looking for other relevant risk factors for the diseases found in this study in their very tall patients.”
The research was funded by the U.S. Department of Veteran Affairs, the Boettcher Foundation’s Webb-Waring Biomedical Research Program, the National Institutes of Health, and a Linda Pechenik Montague Investigator award. One study coauthor is a full-time employee of Novartis Institutes of Biomedical Research. The other authors and Wilson had no disclosures.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
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