The number of persons diagnosed with asthma is on a steady rise, in part as a result of better awareness of the condition. But experts disagree about whether things like air pollution and excessive cleanliness are also to blame.
Asthma rates have climbed by as much as 12 percent over the past decade, but the causes remain clouded in mystery. “Allergy and asthma results from a complicated relationship between a persons genes and the environment,” explains asthma expert Marc Riedl, MD, assistant professor of medicine at UCLA’s David Geffen School of Medicine. “In much of the world, the environment in which people live and develop has evolved rather speedily and significantly since the industrial revolution.” These changes cause allergic inflammation, which results to increasing rates of allergic rhinitis, food allergies, and eczema, as well as increasing rates of asthma.
Children living within 75 meters of areas of high traffic congestion are more likely to develop asthma or have asthma events, especially if they have a family history of asthma or allergies. As traffic congestion increases in the United States and around the world, the nitric oxide, ozone, and particulate matter that exist in air pollution are likely causes of asthma. Some researchers have suggested that giving children additional antioxidants could counter the impact of air pollution on their respiratory system.
2. The Hygiene Hypothesis
The infamous “hygiene hypothesis” as a cause of asthma is long debated, but the premise is as follows: Our effort to keep home, school, and play environments ultraclean, coupled with the use of antimicrobial products to accomplish this, is actually interfering with the natural course of immune system development by removing the infectious agents that help test and strengthen immunity. Some researchers have tied asthma risk to frequent (more than weekly) use of cleaning products themselves, particularly those that are aerosol-based.
For adults with asthma, smoking or being around smokers can be asthma triggers. It turns out that smoking during pregnancy or exposure to secondhand smoke during pregnancy could be asthma causes for infants. Being born to a mother who smoked is strongly correlated with later asthma diagnosis — another good reason to quit smoking cigarettes before or during pregnancy, and stay away from places where people smoke.
4. The Role of Genes
About 70 percent of asthma risk is genetic, which means that if asthma rates are increasing, the genetic switch that turns asthma on in certain people is being flipped more often by changing factors in the environment. In fact, one of the strongest predictors of asthma in childhood is whether your mother had asthma.
In a recent study, researchers from Los Angeles Biomedical Research Institute found that exposing pregnant rats to nicotine had implications for generations to come — both the grand-rats and great-grand-rats had increased risk of asthma, even though the smoking stopped at the first generation. The great-grand rats’ lungs narrowed and contracted more readily in response to asthma triggers, the study, published in American Journal of Physiology-Lung Cellular and Molecular Physiology, found, confirming the theory.
5. Changing Kids’ Diets
Obesity, overweight, and less physical activity all seem to be correlated with asthma, but whether they are causes of asthma is less well understood. Nutrition researchers have proposed that paying more attention to nutrition even while a baby is in the womb could help slow the increase in asthma. Pregnant women and young children might both be more protected against asthma by eating more healthy fats, antioxidants, and probiotics. Not getting enough vitamin D could also put children at risk for asthma.
6. Increased C-Section Rates
Delivery by Cesarean section is correlated with an increased risk of asthma diagnosis in childhood. A C-section causes changes in our gut flora during infancy, says Dr. Riedl. There is some evidence that the “good” bacteria in an infant’s digestive tract helps protect against asthma, and children who might be diagnosed with asthma have measurable differences in these “good” bacteria. C-sections negatively affect this balance. On the other hand, breastfeeding for more than three months seems to protect “gut flora.”
7. Fewer Childhood Infections
No matter how hard parents try, kids will inevitably get sick with a cold. But by avoiding every childhood infection or taking antibiotics for every one, parents could actually be increasing the risk of their child developing asthma. In addition to only taking antibiotics when absolutely necessary, it’s important to completely avoid them in situations where they aren’t helpful, such as viral illnesses like the flu.
8. More Asthma Awareness
“I believe there is actual possibility that increased awareness of asthma by both the public and healthcare providers may be playing a role in the increased rate of diagnosis, as well,” says Riedl. “Recognize, however, that a portion of what we see in the pulmonary or allergy specialist’s office, which has been called ‘difficult asthma,’ is in fact not asthma, but some other condition. So there is some rate of over-diagnosis or misdiagnosis that goes along with this increased awareness.”
What Can Be Done to Prevent Asthma?
“If we wish to reduce the national or global dominance of asthma, we likely need to tackle large public health issues such as air pollution levels, obesity rates, and perhaps the overuse of antibiotics,” says Riedl. Researchers are exploring the possibility of immunotherapies that change the body’s response to allergens. “The immune system is matchless in power, and caution is necessary when trying to modify the human immune response,” he warns.