Ambient air pollution, covert cerebrovascular disease and cognition: results from the ISSYS study

Although air pollution (AP) has been associated with stroke and dementia, data regarding its relationship with covert cerebrovascular disease (cCVD) and cognition over time are sparse. The aim of this study was to explore these relationships.

A prospective population-based study of 976 stroke-free and non-demented individuals living in Barcelona, Spain, was conducted during 2010-2016. A land use regression model was used to estimate the exposure of each participant to AP: NO_x, NO₂, PM_2.5, PM₁₀, PM_coarse and PM_2.5 absorbance. Cognitive function and cCVD were assessed at baseline (n = 976) and 4 years after (n = 317). Multivariate-adjusted models were developed.

At baseline, 99 participants (10.1%) had covert brain infarcts and 91 (9.3%) had extensive periventricular white matter hyperintensities (WMHs). Marked subcortical WMH progression was seen in 19.7%; the incidence of other covert cerebrovascular lessons ranged between 5% and 6% each. PM_2.5 was related to higher odds of having a covert brain infarct (odds ratio [OR] 2.21; 95% confidence interval [CI] 1.06-4.60). PM_2.5 absorbance was related to higher odds of having extensive subcortical WMHs (OR 1.72; 95% CI 1.13-2.60), whereas NO₂ was related to higher odds of having extensive subcortical (OR 1.66; 95% CI 1.17-2.35) or periventricular (OR 1.96; 95% CI 1.10-3.50) WMHs and to higher odds of developing marked subcortical WMH progression (OR 1.40; 95% CI 1.05-1.90). NO_x was related to incident cerebral microbleeds (OR 1.36; 95% CI 1.04-1.79). There was no association between AP and cognition.

Air pollutant predicts the presence and accumulation of cCVD. Its impact on cognitive impairment remains to be determined.