The study builds on the concept of united airways, which describes the link between the upper and lower airways. Explorations of this concept have mainly related to asthma and less to chronic obstructive pulmonary disease (COPD). The aim of this study was to investigate paranasal sinus opacification at magnetic resonance imaging (MRI) in COPD, self-reported asthma and respiratory symptoms. In this cross-sectional study, 880 randomly selected participants in the Nord-Trøndelag health survey (HUNT) (mean age 57.7 years, range 50-66 years, 463 women) were investigated using MRI of the paranasal sinuses. Participants were allocated to four mutually exclusive groups: (1) COPD (n = 20), (2) asthma (n = 89), (3) respiratory symptoms (n = 199), and (4) reference group (n = 572). Paranasal sinus opacifications were categorised as mucosal thickening, polyps and retention cysts, and fluid. In each participant, measurements ≥1 mm from all sinuses were summed to give a total for each category of opacities. The sums for these three categories were further added together, and referred to as the total sum. Using the 75th percentile cut-off values, the likelihood of having paranasal sinus opacifications was more than six times higher in participants with COPD and twice as high in participants with asthma than among the reference group. Respiratory symptoms were only associated with mucosal thickening. The present study shows that paranasal sinus opacification is associated not only with asthma, but also with COPD and respiratory symptoms. This is in accordance with the united airways hypothesis, and should be kept in mind when handling patients with these conditions.
Keywords: Asthma; COPD; Magnetic resonance imaging; Paranasal sinuses; United airways.