Increased prevalence of allergic asthma from 1996 to 2006 and further to 2016-results from three population surveys

Background: During the latter half of the 20th century, the prevalence of asthma and many other allergic diseases has increased. Information on asthma prevalence trends among adults after 2010, especially regarding studies separating allergic asthma from non-allergic asthma, is lacking.

Objective: The aim was to estimate prevalence trends of current asthma among adults, both allergic and non-allergic, from 1996 to 2016.

Methods: Three cross-sectional samples from the same area of Sweden, 20-69 years, participated in surveys with the same questionnaire in 1996 (n=7104 participants, 85% response rate), 2006 (n=6165, 77%) and 2016 (n=5466, 53%), respectively. Allergic rhino-conjunctivitis (ARC) was used as a marker for allergic sensitization to define allergic asthma.

Results: The prevalence of current asthma increased from 8.4% (95% CI: 7.8-9.0) in 1996 to 9.9% (95% CI: 9.2-10.6) in 2006 and 10.9% (95% CI: 10.1-11.7) in 2016 (P<.001). Allergic asthma increased from 5.0% (95% CI: 4.5-5.5) in 1996 to 6.0% (95% CI: 5.4-6.6) in 2006 and further to 7.3% (95% CI: 6.6-8.0) in 2016 (P<.001), while the prevalence of non-allergic asthma remained stable around 3.4%-3.8%. The increase in current asthma was most pronounced among women and among the middle-aged. Physician-diagnosed asthma, asthma medication use and ARC also increased significantly, while the prevalence of symptoms common in asthma such as wheeze and attacks of shortness of breath decreased slightly or was stable. The prevalence of current smoking decreased from 27.4% in 1996 to 12.3% in 2016.

Conclusions and clinical relevance: The prevalence of allergic asthma increased from 1996 to 2006 and further to 2016, while the prevalence of non-allergic asthma remained on a stable prevalence level. The prevalence of symptoms common in asthma decreased slightly or was stable despite a substantial decrease in the prevalence of current smoking. Clinicians should be aware that the previously observed increase in prevalence of allergic asthma is still ongoing.