Associations between exposure to outdoor air pollution and cognitive function in England: the ELSA cohort

Abstract

BACKGROUND AND AIM: The potential role of exposure to air pollution on cognitive health outcomes is yet to be fully understood, although there is an increase in evidence for a negative association between cognition and several pollutants. Here, long-term estimates of NO2, PM10, PM2.5 and O3 were linked to respondents of the English Longitudinal Study of Ageing (n = 8,967 respondents aged 50 years and older) and the effects of each pollutant on cognitive test scores were investigated. METHODS: Annual average CMAQ-urban (Community Multiscale Air Quality) dispersion model estimates were applied to the residential postcode of respondents. A composite memory scale (0-20) incorporated responses to both an immediate and delayed word recall test. The animal naming test was included as a measure of executive function (0-50). Mixed-effects models were implemented separately for each pollutant and for each test, adjusting for age, gender, number of follow-ups, physical activity and smoking status. RESULTS:Respondent score on the composite memory scale decreased by 0.12 per interquartile range (IQR) increase for NO2 (IQR: 12.4μg/m3), as well as decreases of 0.02 for PM10 (IQR: 3.65μg/m3) and 0.08 for PM2.5 (IQR: 2.7μg/m3). An increase in score of 0.25 was reported for ozone per increase in IQR (15.05μg/m3). For executive function scores, negative associations were found for NO2, PM10 and PM2.5, with decreases of 0.29, 0.06 and 0.15, respectively per IQR increase. An IQR increase in ozone increased executive function score by 0.46. All results were statistically significant (p 0.05). CONCLUSIONS:Cognitive function in ELSA respondents decreased as exposure to NO2, PM10 and PM2.5 increased. Both episodic memory and executive function may be affected by long-term exposure to air pollution and further investigation is required to fully determine the extent to which the cognitive health of the elderly population of England may be vulnerable to outdoor air pollution. KEYWORDS: Air pollution, Long-term exposure, Mental health outcomes