Dust mites outlast heroic efforts to help asthma patients

Asthma sufferers might as well stop wasting energy and money on labor-intensive or costly interventions to get rid of household dust, according to a new review of studies.

“We can conclude with confidence that there is no need to buy expensive vacuum cleaners or mattress covers or to use chemical methods against house dust mites, because these treatments do not work,” said lead author Peter Gotzsche, M.D.

Some people with asthma are allergic to tiny eight-legged arthropods known as house dust mites and the allergens from these mites can bring on asthma attacks. Unfortunately, the 54-study review of 3,000 asthma patients finds that no chemical or physical intervention to reduce exposure to house dust mites is effective.

Gotzsche, director of The Nordic Cochrane Centre in Copenhagen, Denmark, said that thousands of specialists have been speculating about this problem and trying all sorts of interventions for many years, but have not found the right answer yet.

Gotzsche and colleagues conducted their first systematic review in 1998; they have updated their review with new studies several times.

Studies, which ranged from about two weeks to two years duration, employed a variety of interventions. Some studies used chemicals to kill mites, while others used physical interventions such as encasing mattresses and pillows in covers that mites cannot get through. Other studies called for frequent laundering of bed linens in hot water or bleach; beating cushions outside; and removing toys, plants and furniture from a home.

Although it seems counterintuitive that such intensive efforts to control dust mites were unproductive, the findings are consistent and clear.

“If you are wondering why it is that mattress covers and the other strategies are not effective, the likely answer is that all these treatments do not have a large enough effect on the occurrence of allergens from house dust mites,” Gotzsche said. “The level of allergens is so high in most homes that what remains after the treatment is still high enough to cause asthma attacks.”

He said that even very low allergen concentrations can affect bronchial distress among sensitive individuals, and most homes host many mites and mite allergens. In addition, mite-sensitive individuals are often sensitive to other allergens, so that successful elimination of a single allergen might have limited benefit at best.

Some of the included studies had obtained reductions of more than 50 percent, and some considerably more, but even reducing environmental allergens by 90 percent is insufficient, Gotzsche said. Before interventions can work, you must reduce allergens far more than you can obtain with the interventions studied thus far.

Gotzsche is critical of 2007 U.S. guidelines from the National Asthma Education and Prevention program, whose Asthma Action Plan for patients recommends interventions such as encasing mattresses and pillows in special dust-proof covers, and washing sheets, blankets and stuffed toys in hot water every week.

“Reviews and guidelines should reflect the facts,” he said. “It is difficult, perhaps, to realize that we cannot really do anything, but there is no evidence to support these guidelines and they are misleading. It is about time specialists start becoming honest with patients.”

Gotzsche described witnessing efforts to market $10,000 vacuum cleaners to vulnerable parents of children with asthma. These machines were not even better than cheap ones at removing dust, he said.

“Parents are sometimes fooled by reckless tradesmen, but it is better not to waste money on interventions that don’t work,” he said.

Noreen Clark, Ph.D., professor of public health at the University of Michigan, described this as an important review. Clark, who also serves as national program director for the Robert Wood Johnson Foundation Allies Against Asthma program, said that when a doctor recommends a management strategy that is difficult to carry out and it fails to produce the desired result, the patient loses confidence in other effective things the doctor has recommended.

“Patient treatment and counseling should focus on a few things that evidence shows will be significant in getting the disease under control,” Clark said. “This study suggests that trying to reduce exposure to dust mites by covering mattresses, using ionizers, washing bedding at high temperatures, and so on, will not help and should not be on the list.”

Source: Center for the Advancement of Health

Related stories:

Munich researchers discover key allergy gene
Together with colleagues from the Department of Dermatology and Allergy and the Center for Allergy and Environment of the Technische Universität München, scientists at the Helmholtz Zentrum München have pinpointed a major gene for allergic diseases. The gene was localized using cutting edge technologies for examining the whole human genome at the Helmholtz Zentrum München.
Asthma costs Californians 3.9 million days of work or school a year
California's children missed 1.9 million days of school and the state's adult workers missed 2 million days of work due to asthma, according to new research from the UCLA Center for Health Policy Research.
Mother's prenatal stress predisposes their babies to asthma and allergy
Women who are stressed during pregnancy may pass some of that frazzlement to their fetuses in the form of increased sensitivity to allergen exposure and possibly future asthma risk, according to researchers from Harvard Medical School who presented their findings at the American Thoracic Society’s 2008 International Conference in Toronto on Sunday.
Immune system pathway identified to fight allergens, asthma
For the first time, researchers from the University of Pittsburgh School of Medicine have identified genetic components of dendritic cells that are key to asthma and allergy-related immune response malfunction. Targeting these elements could result in more effective drugs to treat allergic disorders and asthma, according to a study reported in the May edition of the journal Nature Medicine.
Gene variant increases risk of asthma
A tiny variation in a gene known as CHI3L1 increases susceptibility to asthma, bronchial hyperresponsiveness and decline in lung function, researchers report early online in the New England Journal of Medicine. (The printed version will appear in the April 17 issue). The gene variant causes increased blood levels of YKL-40, a biomarker for asthma. A slightly different version of the genetic variation lowers YKL-40 levels and protects against asthma.
Allergy battle could be won in five years, says scientist
Allergies such as asthma, eczema and hay fever could be snuffed out within five years thanks to pioneering work at The University of Manchester.
‘High efficiency’ vacuum cleaners no better at protecting against dust mites
Researchers at the North West Lung Centre, run by The University of Manchester and based at Wythenshawe Hospital, have discovered that vacuum cleaners with ‘high-efficiency particulate air’ or HEPA filters are no more effective than standard models at reducing exposure to dust-mites.
Innate immune system targets asthma-linked fungus for destruction
A new study shows that the innate immune system of humans is capable of killing a fungus linked to airway inflammation, chronic rhinosinusitis and bronchial asthma. Researchers at Mayo Clinic and the Virginia Bioinformatics Institute (VBI) have revealed that eosinophils, a particular type of white blood cell, exert a strong immune response against the environmental fungus Alternaria alternata. The groundbreaking findings, which shed light on some of the early events involved in the recognition of A. alternata by the human immune system, were published recently in the Journal of Immunology.

News discussion:

Medicine & Health news