But doctors now say that people with moderate to severe asthma should also be taking regular doses of inhaled steroids, to knock down the underlying inflammation that plays a role in the disease both before and during attacks. Because the increase in asthma rates began in the late 1970s, researchers put at the top of their lists of possible causes the airtight, insulated homes that residents in Western societies have built in response to higher energy costs. These energy-efficient homes expose people to stagnant air and higher concentrations of asthma triggers. Foremost among them are cats, cockroaches and dust mites. Cat dander, in particular, is a notoriously powerful and long- lasting allergen.
Cigarette smoke is a prime suspect, but tobacco use is declining in the United States.
And cockroaches, only recently identified as a major asthma trigger, have been around for centuries. Disease detectives also believe that outdoor air pollution, long identified as a problem for asthma sufferers, cannot explain the most recent increase. Since the early 1980s in the United States, concentrations of sulfur dioxide, carbon monoxide, nitrogen dioxide, ozone and particulates have been falling, while asthma rates were soaring. Neonatal intensive care units can save babies who would otherwise have died. But the children often have severe lung damage and grow up with asthma.