High but stable incidence of adult-onset asthma in northern Sweden over the last decades.

BACKGROUND

The prevalence of asthma has increased both among children and adults during the latter half of the 20th century. The prevalence among adults is affected by the incidence of asthma not only in childhood but also in adulthood. Time trends in asthma incidence have been poorly studied.

AIMS

The aim of this study was to review the incidence of adult-onset asthma from 1996 to 2006 and 2006 to 2016 and compare the risk factor patterns.

METHODS

In the Obstructive Lung Disease in Northern Sweden (OLIN) studies, two randomly selected population-based samples in the 20-69-year age group participated in postal questionnaire surveys about asthma in 1996 (n=7104, 85%) and 2006 (n=6165, 77%). A 10-year follow-up of the two cohorts with the same validated questionnaire was performed, and 5709 and 4552 responded, respectively. Different definitions of population at risk were used in the calculations of asthma incidence. The protocol followed a study performed between 1986 and 1996 in the same area.

RESULTS

The crude incidence rate of physician-diagnosed asthma was 4.4 per 1000 person-years (men 3.8, women 5.5) from 1996 to 2006, and 4.8 per 1000 person-years (men 3.7, women 6.2) from 2006 to 2016. When correcting for possible under-diagnosis at study entry, the incidence rate was 2.4 per 1000 person-years from 1996 to 2006 and 2.6 per 1000 person-years from 2006 to 2016. The incidence rates were similar across age groups. Allergic rhino-conjunctivitis was the main risk factor for incident asthma in both observation periods (risk ratio 2.4-2.6).

CONCLUSIONS

The incidence of adult-onset asthma has been stable over the last two decades and has remained at a similar level since the 1980s. The high incidence contributes to the increase in asthma prevalence.

Informations de copyright

Copyright ©The authors 2021.

Déclaration de conflit d'intérêts

Conflict of interest: P. Räisänen has nothing to disclose. Conflict of interest: H. Backman reports personal fees from Boehringer Ingelheim and AstraZeneca outside the submitted work. Conflict of interest: L. Hedman has nothing to disclose. Conflict of interest: M. Andersson has nothing to disclose. Conflict of interest: C. Stridsman reports personal fees from AstraZeneca, Boehringer Ingelheim and Novartis outside the submitted work. Conflict of interest: H. Kankaanranta reports fees for lectures and consulting, and costs for attending an international congress from AstraZeneca, Boehringer Ingelheim and Orion Pharma; fees for consulting and lectures from Chiesi Pharma AB, Novartis and GlaxoSmithKline; fees for lectures from Mundipharma; and fees for consulting from SanofiGenzyme, all outside the submitted work. Conflict of interest: P. Ilmarinen reports a fee for a lecture from and has been an employee of GlaxoSmithKline since March 2021, and reports fees for lectures from Mundipharma and AstraZeneca, and a fee for a lecture and for preparing presentation material from Novartis, outside the submitted work. Conflict of interest: H. Andersen has nothing to disclose. Conflict of interest: P. Piirilä has nothing to disclose. Conflict of interest: A. Lindberg reports personal fees for lectures and an advisory board from Boehringer Ingelheim, personal fees for advisory boards from AstraZeneca and GlaxoSmithKline, and personal fees for lectures from Novartis, outside the submitted work. Conflict of interest: B. Lundbäck reports personal fees for lecturing and advisory meeting participation from Novartis, personal fees for advisory meeting participation from Sanofi, and a grant for a study on study on respiratory epidemiology from AstraZeneca, outside the submitted work. Conflict of interest: R. Rönmark reports grants from the Swedish Heart and Lung fundation, the Swedish Asthma and Allergy Foundation, Norrbotten county council, and ALF (a regional agreement between Umeå University, Västerbotten county council and Norrbotten county council), during the conduct of the study; and lecture fees from AstraZeneca, outside the submitted work.