A decline in aspirin use, exposure to household sprays and cleaners and lack of vitamin D may all help explain surging asthma rates in the past few decades.
For years the hygiene hypothesis has been used to explain stark differences in asthma rates around the world. In Western countries, asthma rates are about 50 times higher than in rural Africa, for instance. The hygiene hypothesis suggests that Westerners have less exposure to bacteria, viruses and parasites, altering the immune response and increasing risk for allergic diseases.
But Dr. Harold S. Nelson, professor of medicine at the asthma and allergy specialty hospital National Jewish Health in Denver, says the hygiene hypothesis doesn’t fully explain rising asthma rates in the United States and industrialized countries. The incidence of asthma has doubled in the United States since the 1980s.
In a recent talk at National Jewish Health’s annual Pulmonary and Allergy Update conference, Dr. Nelson noted that lower levels of vitamin D, exposure to spray cleaning compounds, and a wider use of acetaminophen in place of aspirin have contributed to the asthma epidemic.
The concern with household cleaners is that the spray mist can be inhaled and irritate the lungs, increasing risk for asthma. The biggest culprits appear to be glass cleaners and air fresheners. A major European study of cleaning product use in 10 countries
found that people who used the cleaners four days a week faced double the risk of adult asthma. Weekly use increased risk by 50 percent. Australian researchers have also found
a link with household cleaning sprays and asthma in children.
In a November 2007 article in The Journal of Allergy and Clinical Immunology,
researchers from Brigham and Women’s Hospital in Boston reviewed the evidence showing a link between low vitamin D levels in mothers and childhood asthma. The authors wrote:
We hypothesize that as populations grow more prosperous, more time is spent indoors, and there is less exposure to sunlight, leading to decreased cutaneous vitamin D production. Coupled with inadequate intake from foods and supplements, this then leads to vitamin D deficiency, particularly in pregnant women, resulting in more asthma and allergy in their offspring.
Declining aspirin use may also help explain rising asthma rates. Young children should not be given aspirin because it increases risk for Reye’s syndrome
. But a common alternative, acetaminophen, the ingredient in Tylenol, may increase a child’s risk for asthma when used in very young children or in high doses. The drug lowers levels of the antioxidant glutathione, which can help protect against lung damage caused by oxidants. In a study of more than 200,000 6- and 7-year-olds,
use of acetaminophen in the first year of life was associated with a 46 percent increase in prevalence of asthma symptoms. Children using higher doses of acetaminophen had three times the risk of asthma.
Dr. Nelson notes that the research isn’t conclusive, but that people can take simple measures to lower their exposure to these new risk factors. Use liquid cleaners or pump sprays that don’t generate a fine mist. Eliminate use of spray air fresheners. Pregnant women and mothers should talk to their obstetricians and pediatricians about whether they should consider vitamin D supplements. And parents should discuss pain relievers with the pediatrician. Every pain reliever carries risks, and alternatives to Tylenol like ibuprofen can increase risk for gastrointestinal complaints. However, doctors may recommend switching between pain relievers or limiting exposure to acetaminophen in certain cases.
“There is a lot of supporting evidence for all three of these new risk factors,” Dr. Nelson said.