Table compares the demographic characteristics of patients less than 50 years of age diagnosed with asthma in 2008 between the NAMCS and the NDTI. In general, patient records included in NAMCS were more likely to be those of males (51% vs. 45%), less than 19 years of age (56% vs. 40%), seen by pediatricians (41% vs. 30%). The proportion of individuals with prior visits during the previous 12 months was similar among visits within the NAMCS and the NDTI.
Characteristics of Patients Less than 50 Years of Age Diagnosed with Asthma in 2008
Asthma Treatments by Treatment Class
Table provides examples of the therapeutic classes examined, their availability as generics, their date of FDA approval, and the total volume of use among individuals less than 50 years of age in 2008 based on NAMCS. For example, in 2008 there were an estimated 6.9 million [M] treatment visits in which short acting β2 agonists were mentioned, 3.2M mentions of inhaled steroids, and 1.9M mentions of fixed dose combinations including long acting β2 agonists and inhaled corticosteroids.
Examples of Asthma Medications by Treatment Class, 2008
Trends in Asthma Treatment Visits
Figure depicts trends in the number of NAMCS and NDTI office-based visits for asthma, as well as the fraction of these where one or more asthma treatment was mentioned. During most of the years examined, trends were similar between the two data sources, although NAMCS estimates exhibited much greater yearly variation. Estimates from NAMCS indicated modest increases in the number of annual asthma visits from 9.9 million [M] in 1997 to 10.3M during 2008; estimates from the NDTI suggested more gradual continuous increases from 8.7M in 1997 to 12.6M during 2009. The fraction of annual visits where at least one asthma treatment was mentioned (treatment visits) ranged between 85%–95% (NAMCS) and 96%–98% (NDTI).
Figure 1 Total treatment visits for asthma among individuals less than 50 years of age, United States, 1997–2009 (NDTI and NAMCS). Treated visits represent office based physician visits in which one or more treatments were newly prescribed, renewed, (more ...)
Use of Individual Therapies
There were marked changes in the rates of use of most asthma therapies between 1997 and 2009 (Table ). For example, data from NAMCS suggested decreases in the number of visits where asthma was diagnosed and a treatment was mentioned (treatment visits) with a short-acting β2-agonist, from 80% of treatment visits in 1997 to 71% of treatment visits in 2008. Table also indicates increased inhaled steroid use (24% of treatment visits in 1997 to 33% of treatment visits in 2008), increased use of fixed dose LABA/steroid combinations (0% in 1997 to 19% in 2008), and increased leukotriene use (9% in 1997 to 24% in 2008). In 2008, anticholinergics, xanthines, and LABAs without concomitant steroid accounted for fewer than 4% of all treatment visits.
Percent of Asthma Treatment by Category, 1997–2009*
Comparisons of Estimates from NAMCS with NDTI
Table also reflects similar data from the NDTI. Overall, the patterns were quite similar, with reductions in short-acting β2-agonist use, increases in leukotriene use and the use of fixed-dose long-acting β2-agonist/steroid combinations, and nearly no use of long-acting β2-agonists without concomitant steroids. The two data sources revealed modestly different trends for inhaled steroid mentions, with NAMCS suggesting an increase from 24% of treatment visits (1997) to 33% of treatment visits (2008) and the NDTI suggesting a decline from 39% (1997) to 26% (2008). Overall, the mean absolute difference in the estimated proportion of treatment visits accounted for by each therapy was between 2%–6%, with 5 of 84 annual estimates exceeding 10% between the two data sources.
Trends in Use of Fixed Dose Combinations and LABA Use Without Steroids
Figure a depicts changes in the use of inhaled steroids, long-acting β2-agonists, and LABA/steroid combinations based on data from NAMCS. In contrast to the data in Table , the figure includes both fixed dose combination and extemporaneously combined therapies when depicting treatment visits where combined LABA and steroid therapies were mentioned. There were low levels of LABA mentioned without concomitant steroids even in 1997 (4%), which declined to fewer than 1% of visits where a treatment was used in 2008. By contrast, the number of treatment visits in which LABA/steroid combinations were mentioned ranged between 2% and 8% of treatment visits between 1997 and 2000, then increased markedly between 2000 and 2002 before again reaching a plateau and remaining between 19% and 24% of treatment visits between 2002 and 2008. By 2008, of individuals taking both a LABA and inhaled steroid, 99% of these mentions were through the use of fixed dose combination therapies rather than extemporaneously combined therapies (data not shown). Over the time period, the use of inhaled steroids without concomitant LABA use has remained fairly steady, ranging from 21% (1997) to a peak of 38% (2001) before declining modestly to 33% (2008). Figure b reflects generally similar results using the NDTI.
Figure 2 a. Trends in use of inhaled steroids, long-acting β2-agonists, and steroid/ β2-agonist combination therapy (NAMCS). “Long-acting β2-agonist/steroids" depicts both fixed dose combinations and concurrent use of separate therapies. (more ...)
Use of Controller and Reliever Therapies
The number of mentions of controller therapies in NAMCS increased from 4.5M treatment visits (1997) to a peak of 15.5M uses (2004) and was an estimated 9.4M uses in 2008. NDTI reflected more gradual changes with increasing controller treatment visits from 5.4M visits in 1997 to 14.0M in 2005 and then a modest decrease to 12.7M visits in 2009. Similar to NAMCS, reliever therapies remained relatively stable in NDTI, fluctuating between 6.5M and 8.5M treatment visits between 1997 and 2009. Overall, between 1997 and 2008 the ratio of controller to total therapies increased from 0.4 to 0.6 (NAMCS) and from 0.5 to 0.6 (NDTI).
Analyses of All Individuals Rather than Those Less than 50 Years of Age
Between 1997 and 2007, patients under the age of 50 represented 63%–77% of all visits where asthma was diagnosed in NAMCS. A similar fraction of all asthma patient visits (62%–73%) was accounted for by these individuals in NDTI. Overall, the observed patterns of usage did not differ markedly when analyses were conducted with this less restricted patient cohort.