So, how big a problem is asthma? I don't have to tell pediatricians that it's certainly common, it's certainly a big problem, but it's always interesting to look at numbers. This was a study just published this past year in Pediatrics, many of you may have seen it, and this was from the National Hospital Discharge Survey data from the National Center for Health Statistics at the Center for Disease Control & Prevention accumulated, and what we're looking at now is the frequency of hospitalizations over this almost 20-year period. Here are hospitalization rates for children under 5 years of age, 0-4 year age group. If you look at this across here, you're talking about the median here is roughly 50 per 10,000, that breaks down to 1 in 200 children in the U.S. every year is hospitalized for asthma. That's twice the rate of children 5 to 10 years of age, and almost five times the rate of children 11 to 17 years of age. So, this population is an important target population, and it's not being terribly well addressed, in my opinion, it hasn't in the past, it's not very well addressed by the NHLBI guidelines, and it's not well addressed by the majority of the commercial entities that have anti-asthmatic medications that distribute a lot of the recommendations to you. It hasn't been considered an important target group. And yet, if we want to decrease some of the costs of asthma care, and some of the morbidity, this is the time to start, with pediatricians attempting to do a better job for these very young patients.

I'm going to get into the specifics of how to treat this, but I'd like to give you also a better appreciation of what happens to a child with asthma, what happens after it starts, and we've been fortunate to have a really magnificent study that's gone on for now 35 years, a natural history study of asthma, a summary of which was recently published in the Journal of Allergy and Clinical Immunology this past year. In multiple publications out of this group from Melbourne, Australia, the Children's Hospital in Melbourne, what they did was, let me back up for a second here, in 1963, they had a structured questionnaire as part of a routine health survey of the 30,000 children entering school in Melbourne, Australia. And they structured the questionnaire to elicit symptoms consistent with asthma. They then took from those not only what the incidence of asthmatic symptoms were, but they then did a stratified randomized sample of different patterns of asthma, to see what would happen to them over the long run.

So, the index cases from the stratified randomized sample, involved 479 second graders in 1964, and included 105 who never wheezed, whom they used as controls, 74 with less than five episodes with viral respiratory infections, 104 with five or more episodes of viral respiratory infections, 113 who had symptoms not necessarily associated with viral respiratory infections, and then they subsequently included in the group 83 who had had onset of asthma before age 3 with persistent symptoms at age 10, and pulmonary function abnormalities. They picked these children up at age 10. This was a true natural history study, this was 1964, this was before any of the medications we commonly use, most of these patients were being taken care of by family practitioners in Australia, and it was a noninterventional study, the pulmonology group at Melbourne Hospital was strictly monitoring these patients. They might have given some advice along the way, but they said they found that generally it wasn't followed anyway. This is a true natural history study. And they evaluated these children, and eventually adults, first at age 7, at age 10, at age 14, 21, 28, 35 and 42. And they were able to maintain a very high percentage of follow-up for these patients.

So what happens to them? The cumulative prevalence of asthma at age 7, when they entered this, when they did this initial survey of children entering school, was 20% of the school age population who had a history consistent with symptoms of asthma. And that's consistent with figures from various places in this country also. The point prevalence at ages 14 and 21 was still common, was 12%. However, 75% of these children, or 15% of all children, only had infrequent episodes, 25%, or 5% of all children, had frequent episodes, but only .5% of all children, 1 in 200, developed chronic or persistent asthma. I think that puts the high frequency of asthma, and some of the more serious aspects of asthma a little more in perspective.

What we're looking at now is the clinical expression at age 42 of children who started out with asthma. On the x-axis, we've got the groups of patients they had, those who had less than five viral respiratory infections, five or more with viral respiratory infections, symptoms without viral respiratory infections, and chronic asthma. Looking at how many had no recent asthma at age 42, you get a very nice picture that the more frequent symptoms, the more likely they were to have symptoms without colds or for severe chronic, you get a progressively decreasing likelihood of being symptom-free at childhood. This provides some of the best data for us as pediatricians to address the parents' question, Will my child outgrow asthma? Well, we can't tell them about their child, but we can certainly give them percentages to a greater extent than we ever could before, because of some of these data. However, even among this group who had had less than five episodes of viral respiratory infections, some of them continued to have such episodes, although infrequently. A few, however, about 12% of even this mildest group, had frequent episodes. That number seems to increase as you get to the patients who had more impressive disease when they were younger, and among this group who had had only episodes with viral respiratory infections with five or more, we do have about 10% who had developed persistent asthma. That likelihood increases with this group, and in this group, half of the patients continued to have persistent asthma throughout life.