Dr. Fernando Holguin on Asthma Research
Fernando Holguin, MD, conducts both clinical and epidemiological research related to asthma as the Director of Emory's Translational Asthma Research Program. Dr. Holguin is an Assistant Professor of Medicine at the Emory University School of Medicine in the division of pulmonary and critical care, and he has a joint appointment in the respiratory air pollution health branch at the Center for Disease Control (CDC).
"I've been doing asthma research for probably the last five or six years," says Dr. Holguin, "and the reason I got involved with asthma research is because when I joined Emory University as a faculty member in 2001, I took over the directorship of the Grady Memorial Hospital Asthma and Allergy Clinic. I was very concerned about the severity of asthma in the inner city population and also very concerned about the number of overweight people coming into the clinic that had asthma. That's how I got involved in all of my current projects."
Asthma & Obesity
"Weight gain increases asthma severity and also increases the incidence of asthma," explains Dr. Holguin. "Sometimes it's hard to tell whether asthmatics exercise less and are therefore more likely to gain weight; while that's a possibility, the problem at large is that weight gain increases the risk of asthma. For subjects who have never been diagnosed with asthma, as they gain weight, they increase their risk for developing new onset asthma."
"Our research is focused on trying to understand the association of obesity and asthma severity on a national level using national asthma surveys with the CDC," Dr. Holguin continues. "And clinically, we're trying to understand why weight gain or obesity increases asthma severity. One of the things we're looking at involves studying some of the hormones that are produced by adipose tissue (fat cells) and how those hormones affect the lungs of asthmatics on many different levels. Right now we're seeing, in both animals and humans, that fat-related hormones can be readily detected in the airways, which has never been shown before. We're trying to find out what it is that they do in the lungs, and nobody knows at this point.
"Obesity significantly increases the risk for other diseases that may affect asthma, too. For example, obese subjects may be more likely to experience gastroesophageal reflux disease (GERD), and GERD has been shown to affect bronchial hyperactivity and asthma severity, so that could certainly be playing a role.
"Sleep apnea has been shown to increase the severity of asthma and affect airway inflammation and oxidation.
"More recently, some reports have been showing that obese subjects may have lower levels of magnesium. Clearly, obese subjects have a very different dietary intake than lean subjects. Obesity affects the lungs of asthmatics on many different levels; for example, there are mechanical factors, dietary factors, and hormonal effects."
Asthma & The Hygiene Hypothesis
The hygiene hypothesis posits that a lack of early childhood exposure to infectious agents increases the susceptibility to allergic diseases like hay fever and asthma. The hypothesis suggests that exposure to bacteria and parasites aids in the development of the immune system.
Dr. Holguin describes a study which illustrates the hygiene hypothesis: "One study compared the prevalence of asthma in Mexican Americans born in the U.S. versus that of Mexican Americans born in Mexico who were currently living in the U.S. It showed that Mexican Americans born in Mexico had significantly lower rates of asthma than those born in the U.S. The [asthma rates] for those born in the U.S. closely approximated American asthma rates for adults.
"One hypothesis to explain those marked differences is the hygiene hypothesis. Perhaps subjects who migrated from Mexico were exposed to less hygienic environments. Clearly, worldwide data supports the idea that people coming from rural areas have a much lower prevalence of allergies and asthma. When they migrate to the U.S., there's a process of culturization in which they take on many characteristics (both good and bad) that are inherent to living in the U.S. There's the fact that when Mexicans come to the U.S., they tend to gain weight. Weight gain could be a part of this phenomenon."
Asthma & Air Quality
From high ozone levels to particulate air pollution, poor air quality can cause both respiratory and cardiovascular problems, and asthmatics are particularly susceptible to the ill effects of air pollution.
"It's well known that high ozone levels contribute to asthma severity and even asthma incidence," says Dr. Holguin. "And now there are now epidemiological studies which show that obese subjects may be more at risk for adverse effects from air pollution. Some experimental animal studies have shown, for example, that obese mice are more likely to respond to ozone adversely. Obesity, then, may be related to the effects of air pollution on some level."
Next fall, Dr. Holguin plans to work on an air quality study funded by the Environmental Protection Research Institute (EPRI): "It's a very large, comprehensive study on the cardiovascular effects of particulate air pollution here in Atlanta. We'll look at air pollution exposure with individuals as well as animals and try to understand why airborne particles affect vascular function. These particles have been associated with stroke and myocardial infarction [heart attack], even at ambient levels that would be considered safe by national air quality standards."
Virtual Reality for Smoking Cessation
Tobacco smoke is a major asthma trigger (and carcinogen) and especially harmful to the lungs of people who suffer from asthma. Dr. Holguin has been working on a very interesting new technique to help people quit smoking - and it's based on virtual reality.
"It hasn't been published yet," says Dr. Holguin, "but it seems like virtual reality is really helping people be a lot more successful compared to the patch alone. The way the virtual reality works is that subjects are exposed to scenarios that stimulate their craving cigarettes, and then they undergo counseling techniques that help them deal with the cravings. Apparently, so far it's been very, very effective. I think this technique will be very useful in the future, alongside other pharmacological and psychological therapies, to help people be more successful in achieving long-term smoking cessation. One of the things that's really nice about virtual reality is that it's a therapy with no side effects, but it can help a lot psychologically."
Future Asthma Research
Dr. Holguin gives a preview of additional upcoming asthma research projects: "This fall, we're also beginning a brand-new, randomized, placebo-controlled study where we'll be using a new diabetes drug to see if we can offset or reduce the airway inflammation in obese asthmatics when it's not fully controlled with standard asthma therapies. We're also participating in a national bronchial thermoplasty study to treat very severe asthma.
To learn more about asthma, see the Asthma Solution Guide.