Background: Few studies have examined exposure to air pollution and greenness over three decades and incidence of symptoms common in obstructive respiratory disease.

Aim: We investigated incidence of protracted cough in relation to exposure to particulate matter (PM_2.5 and PM₁₀), black carbon (BC), nitrogen dioxide (NO₂), ozone (O₃) and greenness (normalized difference vegetation index (NDVI)).

Methods: We analyzed outcome data from the fourth Respiratory Health in Northern Europe (RHINE IV) study in 2022 (n = 9910 participants aged 50-75 years) as related to modelled air pollution and greenness exposure from 1990, 2000 and 2010. We used Poisson regression model with log person-year at risk as the offset, adjusting for covariates in 2010 (age, sex, smoking status, pack-years smoking, body mass index, education and marital status).

Results: We identified 624 incident cases of protracted cough during 13.0 years mean follow-up. The adjusted incidence rate ratios (IRR) (95% confidence interval (CI)) for protracted cough were 1.29 (1.05-1.57) and 1.23 (1.07-1.42) per 9.7 µg/m³ increase in PM_2.5 and per 0.6 µg/m³ in BC, respectively in 1990 exposure. Similar associations were seen for PM₁₀ and NO₂, but not statistically significant. No association was seen for NDVI whereas O₃ was inversely associated with protracted cough across all time points, the adjusted IRR was 0.80 (0.69-0.94) per 10.9 ?g/m³ increase in O₃ in 1990 exposure.

Conclusion: Long-term exposure to low-level PM_2.5 and BC increased risk for incident symptoms of protracted cough, while O₃ had an inverse association. Living in green neighborhoods was not associated with cough in our study.