Background Despite the well-documented research on the impact of air pollution on health, limitations in data, study designs, health outcomes selection, spatial considerations, and assessments of long-term exposures exist. In this study, we assessed the association of 16-years exposure to air pollution with all-cause and cause-specific hospital admissions in Scotland.

Methods We followed a ‘Scottish Longitudinal Study (SLS)’ cohort of 202,237 individuals aged 17+ for 16 years (2002–2017; N=2,810,414 observations). The SLS dataset was linked to yearly concentrations of four pollutants (NO₂, SO₂, and particulate-matter PM10 and PM2.5) at 1-Km spatial resolution using the individual’s residential postcode. Multilevel mixed-effects negative binomial regression was used to examine the association between air pollution and all-cause, cardiovascular, respiratory, infectious, mental/behavioural disorders, and other-causes hospital admissions. We accounted in our models for the spatial autocorrelation (SA) of air pollution between neighbouring postcodes by computing Local-Geary’s C_0–1 score, a novel local neighbourhood-similarity measure.

Results Higher rates of all-cause, cardiovascular, infectious, mental/behavioural disorders, and other-causes hospital admissions were observed with increasing concentrations of NO₂, PM10, and PM2.5 pollutants. Hospital admissions for respiratory diseases were associated with higher exposure to all the four pollutants including SO₂. For example, the incidence-rate for respiratory hospital admissions increased by 12.5% (95%CI=9.7%-15.5%), 6.8% (95%CI=5.1%-8.5%), 2.2% (95%CI=0.5%-4.0%), and 1.9% (95%CI=1.5%-2.4%) per 1 µg/m³ increase in average cumulative exposure to PM2.5, PM10, SO₂ and NO₂ pollutants, respectively. Accounting for SA reduced the association magnitude between SO₂ and hospital admission outcomes.

Conclusion By linking large register-based longitudinal data to air pollution at a fine spatial resolution over a period of 16 years and controlling for SA, this study highlights the harmful effect of air pollution on health manifested in higher rates of hospital admissions for various disease outcomes. Thus, interventions on air pollution through stricter environmental regulations could help ease the hospital-care burden.