Clinical effects of air pollution on the central nervous system; a review

Abstract

The purpose of this review is to describe recent clinical and epidemiological studies examining the adverse effects of urban air pollution on the central nervous system (CNS). Air pollution and particulate matter (PM) are associated with neuroinflammation and reactive oxygen species (ROS). These processes affect multiple CNS pathways. The conceptual framework of this review focuses on adverse effects of air pollution with respect to neurocognition, white matter disease, stroke, and carotid artery disease. Both children and older individuals exposed to air pollution exhibit signs of cognitive dysfunction. However, evidence on middle-aged cohorts is lacking. White matter injury secondary to air pollution exposure is a putative mechanism for neurocognitive decline. Air pollution is associated with exacerbations of neurodegenerative conditions such as Alzheimer’s and Parkinson’s Diseases. Increases in stroke incidences and mortalities are seen in the setting of air pollution exposure and CNS pathology is robust. Large populations living in highly polluted environments are at risk. This review aims to outline current knowledge of air pollution exposure effects on neurological health.

Association between Exposure to Air Pollution and Total Gray Matter and Total White Matter Volumes in Adults: A Cross-Sectional Study

“…These findings showing associations between air pollution and total gray-matter and total white-matter volumes are consistent with previous studies that found associations between exposure to air pollution and brain changes [1,5,11]. Specifically, a study of older women from the Women's Health Initiative Memory Study (WHIMS; age range 71 to 89 years; N = 1403) found that PM 2.5 was associated with reduced white-matter volume and total brain volume but not gray-matter volume [10].…”

“…In fact, the World Health Organization estimated that in 2016, 91 percent of people across the world lived where exposure to air pollution exceeded their published standards [2]. In addition to its associations with cardiovascular disease [3,4], emerging research suggests that exposure to air pollution might be associated with changes in brain volume and structure [5]. While the mechanisms by which exposure to air pollution could affect brain volume and structure are not fully understood, a variety of factors suggest possible mechanisms by which exposure to air pollution could affect brain structure and function.…”

“…In addition, air pollution has been associated with inflammation and oxidative stress, factors that could also influence brain structure and function [7]. Exposure to air pollution has been associated with altered cortical development [8] and brain structure [5]. In addition to possible associations between exposure to air pollution and reduced volume in specific brain regions, such as smaller hippocampal volume [9], exposure to air pollution might also be associated with reduced overall gray-matter and white-matter volume.…”

Association between air pollution and sleep disordered breathing in children

“…Different pollutants have been associated with systemic inflammation, especially in the respiratory tract and also in eliciting neuroinflammation . Children are particularly susceptible to air pollution; their airway epithelium is more permeable to air pollutants, and their immune defense mechanisms are not fully developed.…”

“…Air contaminants may cause or worsen sleep‐related respiratory symptoms. In adults, studies have revealed significant associations between obstructive sleep apnea (OSA) and air pollution in the context of systemic inflammation, elevated blood pressure, and cardiovascular mortality . There are, however, few studies that have assessed how environmental pollution affects the risk and severity of sleep disordered breathing (SDB) .…”