Results
Period Prevalence Rates
Within the study period, the highest annual PPRs were found for budesonide (between 75.6 and 90.6 per 10,000 persons) and the fixed combination of salmeterol/fluticasone (between 62.1 and 73.1 per 10,000 persons). In contrast, the lowest PPRs were observed for mometasone (between 0.1 and 1.8 per 10,000 persons, Additional file 1: Table S1 http://www.biomedcentral.com/1471-2466/15/55/additional). From 2004 to 2008, a significant increase in PPRs was revealed for formoterol, fixed combinations of salmeterol/fluticasone, formoterol/beclometasone, formoterol/budesonide, and the ICS beclometasone and budesonide. For all remaining drugs including salmeterol, a decrease was found between 2004 and 2008 (all p-values <0.0001; Figure 1). In addition, a slight decrease was found for salmeterol/fluticasone (between 2005 and 2008), and for formoterol and formoterol/budesonide (between 2007 and 2008).
(Enlarge Image)
Figure 1.
Annual period prevalence rates per 10,000 persons stratified by compound between 2004 and 2008.
Analysis of Concomitant LABA and ICS Usage
In total, 307,358 patients (approximately 2.9% out of all insured people) with a documented diagnosis of asthma or status asthmaticus were treated with at least one drug of interest in 2008. The highest proportion (57.6%) of patients was classified as "concomitant LABA and ICS users" followed by "ICS users without LABA" (31.4%, Table 2 ).
The proportion of asthma patients classified as "concomitant LABA and ICS users" increased from 52.0% (2004) to 57.6% (2008, p < 0.0001), whereas the proportion of patients classified as "LABA users without ICS" decreased from 2004 onwards (2004: 6.5%; 2008: 5.4%, p < 0.0001). The proportion of "switchers" decreased slightly during the study period (2004: 5.4%; 2008: 4.8%, p < 0.0001) and the proportion of "non-concomitant LABA and ICS users" increased slightly during the study period (2004: 0.55%; 2008: 0.63%, p = 0.0020). For patients classified as "ICS users without LABA", we found a decrease within the study period (2004: 35.6%; 2008:31.4%, p < 0.0001, Table 3 ).
The age and sex distribution (for the year 2008) for each treatment category is presented in Table 2 . The mean age was the lowest in the "ICS users without LABA" group with 37.5 (standard deviation (SD): 24.9) years and the highest in the "switchers" group with 59.1 (SD: 17.8) years. In each group, more than half of all patients were females. In the "non-concomitant LABA and ICS users" group, the proportion of females was the highest (61.2%).
The proportion of patients with at least one LABA prescription without concomitant ICS (combined analysis of "LABA users without ICS", "non-concomitant LABA and ICS users", "switchers") was the lowest (1.3%) in the age group 0–9 years, increased continuously over the age groups, peaked in patients aged 80–89 years (19.1%) and was followed by a small decrease for patients in the age group "90+" years (18.8%, Table 4 ). Regarding sex-related differences, the proportion of patients with at least one LABA prescription without concomitant ICS was slightly higher in men reaching more than 20% in men aged over 70 years (70–79 years: 20.3%, 80–89 years: 21.3%, "90+": 21.4%; Table 4 ). In these elderly male patients, a concomitant diagnosis of COPD (i.e. asthma-COPD overlap syndrome) was present in 76.8% (Additional file 1: Table S2 http://www.biomedcentral.com/1471-2466/15/55/additional).
Concomitant LABA and ICS Users – Fixed Combination Versus Separate Inhalers
Out of all "concomitant LABA and ICS users", the proportion of patients receiving LABA and ICS only in a fixed inhaler device ("combined inhaler") was high and increased significantly from 82.2% to 85.7% within the study period (p < 0.0001, Table 5 ).
The fraction of patients receiving at least one prescription of a fixed LABA/ICS device, and in addition a separate ICS- or a non-fixed LABA/ICS-prescription ("combinations") decreased from 5.7% to 4.9% (p < 0.0001). On the other hand, patients classified as "concomitant LABA and ICS users" receiving LABA and ICS only in separate inhalers decreased significantly from 12.1% to 9.5% (p < 0.0001, Table 5 ). The proportion of those patients with two separate inhalers was highest in men and women between ages of 50 and 79 years and no differences were found for sex ( Table 6 ).