Air Pollution and Dementia: A Systematic Review

Area of Science:

• Environmental Health
• Neuroscience
• Epidemiology

Background:

• Air pollution and dementia represent significant and escalating global health challenges.
• Plausible biological mechanisms suggest a link between exposure to specific air pollutants and dementia development.

Purpose of the Study:

• To systematically review existing evidence on the relationship between air pollution exposure and the incidence of dementia and cognitive decline.
• To synthesize findings from longitudinal studies investigating the impact of ambient air pollutants on cognitive health.

Main Methods:

• A comprehensive literature search was conducted across Medline, Embase, and PsychINFO databases up to September 2018.
• Included longitudinal studies on adult exposure to air pollution and dementia/cognitive decline, excluding tobacco smoke and occupational exposures.
• Data extraction and validity assessment followed standard Cochrane methodology.

Main Results:

• Thirteen relevant studies from five countries (USA, Canada, Taiwan, Sweden, UK) were identified, with follow-up periods ranging from 1 to 15 years.
• Increased exposure to particulate matter ≤2.5 (PM2.5), nitrogen dioxide (NO2)/nitrous oxides (NOx), and carbon monoxide (CO) was associated with a higher risk of dementia.
• The association between air pollutant exposure and general cognitive decline was less consistent.

Conclusions:

• Emerging evidence indicates that higher exposure to airborne pollutants is associated with an elevated risk of developing dementia.
• The findings underscore the potential neurotoxic effects of common air pollutants.