Associations between air pollution and multimorbidity in the UK Biobank: A cross-sectional study

Background: Long-term exposure to air pollution concentrations is known
to be adversely associated with a broad range of single non-communicable
diseases, but its role in multimorbidity has not been investigated in the UK. We
aimed to assess associations between long-term air pollution exposure and
multimorbidity status, severity, and patterns using the UK Biobank cohort.
Multimorbidity status was calculated based on 41 physical
and mental conditions. We assessed cross-sectional associations between
annual modeled particulate matter (PM)2.5, PMcoarse, PM10, and nitrogen
dioxide (NO2) concentrations (µg/m3–modeled to residential address) and
multimorbidity status at the baseline assessment (2006–2010) in 364,144
people (mean age: 52.2 ± 8.1 years, 52.6% female). Air pollutants were
categorized into quartiles to assess dose-response associations. Among
those with multimorbidity (≥2 conditions; n = 156,395) we assessed
associations between air pollutant exposure levels and multimorbidity severity
and multimorbidity patterns, which were identified using exploratory factor
analysis. Associations were explored using generalized linear models adjusted
for sociodemographic, behavioral, and environmental indicators.
Higher exposures to PM2.5, and NO2 were associated with
multimorbidity status in a dose-dependent manner. These associations were
strongest when we compared the highest air pollution quartile (quartile
4: Q4) with the lowest quartile (Q1) [PM2.5: adjusted odds ratio (adjOR)
= 1.21 (95% CI = 1.18, 1.24); NO2: adjOR = 1.19 (95 % CI = 1.16, 1.23)].

We also observed dose-response associations between air pollutant exposures
and multimorbidity severity scores. We identified 11 multimorbidity patterns.
Air pollution was associated with several multimorbidity patterns with
strongest associations (Q4 vs. Q1) observed for neurological (stroke, epilepsy,
alcohol/substance dependency) [PM2.5: adjOR = 1.31 (95% CI = 1.14, 1.51);
NO2: adjOR = 1.33 (95% CI = 1.11, 1.60)] and respiratory patterns (COPD,
asthma) [PM2.5: adjOR = 1.24 (95% CI = 1.16, 1.33); NO2: adjOR = 1.26 (95%
CI = 1.15, 1.38)].
Conclusions: This cross-sectional study provides evidence that exposure
to air pollution might be associated with having multimorbid, multiorgan conditions. Longitudinal studies are needed to further explore
these associations.