Massive study offers more evidence that environment causes asthma

Though asthma is caused by many things, there are no mistaking the symptoms: your airways are swollen shut, and you can barely breathe. Now a new study of thousands of people reveals how asthma starts. Often, it's with second-hand smoke.

That smoke could come from people around you, or smoke-like environmental toxins. The bad news is that the explosion in asthma cases since the 1970s may be caused by changes to our environment that can't easily be undone. But there's good news too. Researchers who conducted the study say they have a much better idea about who is at risk of developing asthma, which means preventative drugs or other measures could prevent the condition from developing in the first place.

Venderbilt University Medical Center professor Emma Larkin and her colleagues reported this week at the American Thoracic Society conference about the progress they've made with a study of nearly 66,000 women with no history of asthma. Knowing that the body's antioxidant system is connected to asthma, Larkin and colleagues collected blood samples from all the women, noting the levels of antioxidants in their bodies. Antioxidants help our bodies flush out molecules called oxidants that, in small doses, are beneficial - but in large doses can cause cell damage.

Over the course of the study, which is set to last many years, many of the women developed asthma.

Said Larkin:

We found that the host antioxidant defense system is compromised among those destined to develop asthma, and therefore these individuals may be less able to handle environmental exposures that may cause asthma. Oxidative stress, which is a relative increase of oxidants over antioxidants, is known to be important in many diseases, including asthma. It's a battle between charged oxygen species that produce damage and our body's ability to fight them off.

The common thread between the women who developed asthma was exposure to smoke and smoke-like toxins in the environment, as well as a weakened antioxidant defense system. They just weren't able to rally their antioxidant defense system to defeat the onslaught of oxidants. As a result, they suffered cell damage and began exhibiting asthma symptoms.

Larkin cautioned that this doesn't necessarily mean that these women weren't taking in enough antioxidants like Vitamins A, C, and E. Her team also studied the whole enzymatic system the body uses to deploy these antioxidants. Weaknesses in that system seem to be a what allows asthma to develop. This ongoing study is one of the few to examine the antioxidant systems of people before and after they get asthma, and therefore the results are key to controlling the disease.

Added Larkin:

Because this study helps us understand what is occurring in the body prior to the development of symptomatic asthma, the results may point us to nutrients or classes of drugs that could be studied to prevent asthma in those who are high-risk.

You can see the abstract of Larkin's paper on the American Journal of Respiratory and Critical Care website.

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