Air Pollution, Parental Stress Can Affect Risk for Asthma

< Jul. 22, 2009 > -- In addition to automobile exhaust, a new study finds that parents with high stress levels can also affect a child's risk for developing asthma.

For children exposed to smoking while still in the womb, which is another asthma risk, parental stress also increases the risk for asthma, the researchers noted.

The report is published in the Proceedings of the National Academy of Sciences.

About 22.2 million people in the US have been diagnosed with asthma, with at least 6.5 million of them children under the age of 18. Asthma is the leading serious chronic illness among children in the US. It accounts for 14 million absences from school each year, and is the third-ranking cause of childhood hospitalizations under the age of 15.

"There is an association between air pollution and asthma, and it grows with increasing exposure to stress in the household," says lead researcher Ketan Shankardass, Ph.D., a postdoctoral research fellow at the Centre for Research on Inner City Health at The Li Ka Shing Knowledge Institute of St. Michael's Hospital in Toronto, Ontario, Canada.

Dr. Shankardass says the cause of asthma is still unknown. "It's a major illness that affects a lot of people all around the world and we still don't really have a handle on what causes it so we can't control it very well. But this finding contributes to our understanding of that causal process," he says

Air Pollution, Asthma Associated

For the study, Dr. Shankardass and his colleagues collected data on 2,497 children in southern California. The children, aged 5 to 9, had no history of asthma or wheezing when the study started. Over three years, the researchers tracked whether or not the children developed asthma.

The researchers also had the parents fill out a questionnaire that measured stress. The questionnaire assessed the child's mother about feeling in control of her life and being able to handle problems or whether she had problems coping with her life, says Dr. Shankardass.

In addition, the study authors also collected data on the children's exposure to traffic-related pollution and whether the children were exposed to tobacco smoke before birth.

Stress Alone Not a Risk

The researchers found that by itself, stress or socioeconomic status did not increase the risk of developing asthma.

However, when parental stress was combined with traffic pollution or exposure to smoking before birth, the risk of asthma increased more than it did for children exposed to pollution or smoke, but not stress.

Dr. Shankardass notes that exposure to traffic pollution and prenatal smoking as well as stress are more common in lower socioeconomic areas, which may help explain why asthma may disproportionately affect children of disadvantaged parents.

"For once, we may have a piece of the puzzle that would explain the social disparities in asthma," he says.

Stress and the Immune System

Dr. Clifford Bassett, medical director of Allergy and Asthma Care of New York, says it is not surprising that parental stress can have an impact on children and asthma.

"Stress does have an impact on the immune system. Clearly, the relationship between stress, tobacco and air pollution are all bad guys," Dr. Bassett says.

"There are many different variables - behavioral, socioeconomic, environmental, and physiologic - that dictate whether a child will develop asthma," Dr. Bassett adds. "There are a lot of biologic pathways that are involved in the relationship of asthma and stress and the immune system."

Dr. Bassett also thinks gauging household stress should be part of treating children with asthma.

Always consult your child's physician for more information.

What is Asthma?

Asthma is a chronic, inflammatory disease in which the airways become sensitive to allergens (any substance that triggers an allergic reaction). Several things happen to the airways when a child is exposed to certain triggers:

• The lining of the airways become swollen and inflamed.
• The muscles that surround the airways tighten.
• The production of mucus in increased, leading to mucus plugs.

All of these factors will cause the airways to narrow, thus making it difficult for air to go in and out of your child's lungs, causing the symptoms of asthma.

The exact cause of asthma is not completely known. It is believed to be partially inherited, but it also involves many other environmental, infectious, and chemical factors.

After a child is exposed to a certain trigger, the body releases histamine and other agents that can cause inflammation in your child's airways. The body also releases other factors that can cause the muscles of the airways to tighten, or become smaller. There is also an increase in mucus production that may clog the airways.

Some children have exercise-induced asthma, which is caused by varying degrees of exercise. Symptoms can occur during, or shortly after, exercise. Each child has different triggers that cause the asthma to worsen. You should discuss this with your child's physician.

The changes that occur in asthma are believed to happen in two phases:

• An immediate response to the trigger leads to swelling and narrowing of the airways. This makes it initially difficult for your child to breathe.
• A later response, which can happen four to eight hours after the initial exposure to the allergen, leads to further inflammation of the airways and obstruction of airflow.

Although anyone may have asthma, it most commonly occurs in:

• children and adolescents ages 5 to 17 years
• a child with a family history of asthma
• children who have allergies
• children who have exposure to secondhand tobacco smoke.

Always consult your physician for more information.