Vol. 11 •Issue 8 • Page 13
Allergy & Asthma
New Studies Highlight Links Between Asthma, Stress and Hygiene
A growing number of theories are emerging to explain why asthma rates have been skyrocketing for the past two decades. They range from the unusual to the obscure.
Take for instance a recent study that found taking tests is a health hazard. Researchers monitored 20 college students toughing out final exam week and found that test stress may increase allergic response to inhaled allergen, which, in turn, could cause asthma exacerbations.1
New studies regarding factors that protect children from asthma are equally off the beaten path. Attending day care, hanging out on a farm, and early exposure to cats may ward off the disease.
While these studies may seem varied, they’re building a body of evidence that suggests stress and hygiene play a significant role in the epidemiology of asthma.
“I think many people would agree that stress or emotional distress is important when we are talking about someone who already has asthma,” said Rosalind Wright, MD, MPH, principal investigator with the Asthma Coalition on Community, Environment and Social Stress at the Channing Laboratory of Brigham and Women’s Hospital, Boston. “The challenge currently is to try to find out if stress we experience in our daily lives may be contributing to the root causes of the rising asthma epidemic.”
Dr. Wright works with lower-income and minority populations who have high rates and severity of asthma. While part of the reason for these higher rates might be chalked up to genetics or the physical environment these people live in, she believes the daily anxiety these groups encounter, in the forms of poverty and violence, also may be a major epidemiological factor.
“When you marginalize people you start to see crime increase and violence increase as a marker of social and economic strain,” Dr. Wright said.
Normally, when faced with an occasionally stressful or dangerous situation, the body increases production of adrenaline and cortisol, among other things. But for people in the inner city who are dealing with seemingly unending pressure, this production may be more constant.
“This throws off the balance of your body,” she said. The immune system may be affected, so those who are more genetically predisposed to asthma may find themselves at increased risk.
Also, if people are extremely stressed, they may not adhere as well to their asthma medications. They may be depressed or less focused, so they won’t be able to perceive their asthma symptoms as well. They may turn to smoking as a coping mechanism, harmful behavior to any person with asthma in a household.
And if caregivers aren’t letting their children outside because of fear, then those youngsters will miss out on crucial exercise that builds their lungs’ power. If they have asthma, the children are at increased exposure to indoor allergens. The house essentially becomes a prison, and the caregiver’s strain often filters down to the children.
However, those who downplay the link between stress and asthma say that stress has always been around throughout history, so it has nothing to do with rising asthma rates.
“People say to me, ‘What about the Depression?'” Dr. Wright said. The Depression and other stressful times may be different than today, a period when social disconnectedness and income inequality are increasing. “Everybody was in the same boat (in the Depression),” she said. “That might be different than someone feeling marginalized and disconnected in many ways (like today).”
GERMS ARE GOOD
Another tract of asthma research focuses on the hygiene hypothesis, which states that exposure to germs, especially at an early age, is good for the immune system.
In fact, the beneficial effects start at birth, according to A. Sonia Buist, MD, pulmonologist and professor of medicine at Oregon Health & Science University, Portland. Dr. Buist worked on a number of abstracts at the American Thoracic Society’s meeting in Atlanta this year regarding babies and asthma. One found that babies born by cesarean section were at an increased risk for asthma.2
“When you come down the birth canal, you’re bombarded with a large number of organisms,” said Dr. Buist, pointing out that those organisms are important for the development and strengthening of the immune system. “(With a cesarean section), you don’t have the same sort of onslaught.”
Another of Dr. Buist’s abstracts stated that twin babies were at a decreased risk for asthma.3 “If there’s multiple kids, you’re more likely to have germs,” she said.
If you follow this rationale, then day care is another good place for germs. Protection against asthma seems to develop in children who spend the first year of life in day care, especially the first six months, said James E. Gern, MD, associate professor of pediatrics, University of Wisconsin-Madison.
However, “it’s a two-edged sword with day care,” he said. “These kids do seem to have less asthma later in life.” But they also have a higher risk for common cold, ear infections and viral infections that cause wheezing.
Farms appear to be another good place for lungs. Last year, a Lancet article stated that exposure to stables and consumption of farm milk in children less than 1 year old was associated with lower rates of asthma.4
The idea that animals and their uncleanliness may be healthy extends even to cats, long thought to be a scourge to young lungs. Another Lancet article from last year showed that high levels of cat allergen can decrease the risk of asthma in some children.5
An abstract, presented at ATS this year, concluded that children without a maternal family history of asthma who were exposed to a cat in the first year of life were at reduced risk for wheezing. However, if the child’s mother has asthma, early exposure to a cat is associated with an increased risk of asthma for the child.6 x
1. Liu LY, Coe CL, Swenson CA, Kelly EA, Kita H, Busse WW. School examinations enhance airway inflammation to antigen challenge. Am J Respir Crit Care Med. 2002;165(8):1062-67.
2. Renz-Polster H, Buist AS, Vollmer WM, O’Connor E, Frazier A, Wall MA. Being born by .c-section is associated with an increased risk of asthma and allergic rhinoconjunctivitis as a child [abstract]. Am J Respir Crit Care Med. 2002;165(8):A126.
3. Renz-Polster H, Buist AS, Vollmer WM, O’Connor E, Frazier A, Wall MA. Being born as a twin is associated with a decreased risk of asthma, but not of other atopic disorders as a child [abstract]. Am J Respir Crit Care Med. 2002;165(8):A126.
4. Riedler J, Braun-Fahrlander C, Eder W, Schreuer M, Waser M, Maisch S, et al. Exposure to farming in early life and development of asthma and allergy: a cross-sectional survey. Lancet. 2001;358:1129-33.
5. Platts-Mills T, Vaughan J, Squillace S, Woodfolk .J, Sporik R. Sensitisation, asthma, and a modified .Th2 response in children exposed to cat allergen: a .population-based cross-sectional study. Lancet. 2001;357:752-56.
6. Celedon JC, Litonjua AA, Ryan L, Sredl D, Weiss ST, Gold DR. Exposure to cat in early life and wheezing in the first years of life [abstract]. Am J Respir Crit Care Med. 2002;165(8):A244.
John Crawford is assistant editor of ADVANCE.
Unusual Findings of Asthma Studies
A sampling of recent studies on asthma protective measures and risk factors finds researchers covering territory that’s unusual and obscure.
• British researchers discovered that the whole “apple-a-day-keeps-the doctor-away” thing has a ring of truth to it. In their research, people who ate at least two apples per week had a 22 percent to 32 percent lower risk of developing asthma. The reason? Apples are high in flavonoids, which are strong antioxidants.1
• Those same researchers found that drinking one to two glasses of red wine, also high in flavonoids, per day can lower the severity of asthma for people with the disease.1
• A recent study in Thorax warns that getting wet isn’t the only thing to worry about when caught in a thunderstorm. That’s because thunderstorms can cause epidemics of asthma exacerbations during the spring and summer months, as storms can sweep up pollen grains and concentrate them in a shallow area at ground level.2
• According to a study in the Journal of Allergy and Clinical Immunology, exclusively breastfeeding infants for at least four months gives them protection from developing asthma. Whether the mother has asthma isn’t a factor.3
1. Shaheen SE, Sterne JAC, Thompson RL, Songhurst CE, Margetts BM, Burney PGJ. Dietary antioxidants and asthma in adults. Am J Respir Crit Care Med. 2001;164(10):1823-1828.
2. Marks GB, Colquhoun JR, Girgis ST, Koski MH, Treloar AB, Hansen P, et al. Thunderstorm outflows preceding epidemics of asthma during spring and summer. Thorax. 2001;56(6):468-71.
3. Oddy WH, Peat JK, de Klerk NH. Maternal asthma, infant feeding, and the risk of asthma in childhood. J Allergy Clin Immunol. 2002;110:65-7.