Asthma, asthma control and risk of ischemic stroke: The HUNT study

Background: Asthma, a chronic inflammatory airway disease, shares common pathophysiological mechanisms with ischemic stroke. The aim of the study is to assess the association between asthma, levels of asthma control and ischemic stroke risk in men and women and by smoking habits. 

Methods: This prospective population-based cohort study utilized data on 58 712 adults from HUNT Study in Norway free from stroke. Self-reported asthma was categorized as ever asthma, non-active asthma and active asthma (i.e., being on asthma medication within 12 months of the baseline). Asthma control was defined according to the Global Initiative for Asthma questionnaire and was categorized into controlled and not controlled asthma. Stroke was ascertained by linking HUNT data with Nord-Trøndelag hospital records and the Norwegian Patient Registry. 

Results: During a mean follow-up of 17.3 ± 5.3 years, 2619 participants (4.5%) had a first stroke. Not controlled asthma was associated with a modest increased risk of stroke (adjusted HR 1.34, 95%CI 1.03–1.73). Subgroup analyses revealed that the respective association was stronger among those with history of smoking (HR 1.48, 95%CI 1.10–2.00) and males (HR 1.55, 95%CI 1.12–2.16) while absent in non-smokers (HR 1.02, 95%CI 0.61–1.70) and females (HR 1.05, 95%CI 0.69–1.60). Likewise, active asthma was associated with similar increased stroke risk among smokers and males and absent in non-smokers and females. 

Conclusions: Symptomatic and active asthma was associated with a modest increased relative risk for ischemic stroke in smokers and males. Future studies should clarify the difference in risks and mechanisms between different phenotypes of asthma.