New research from an international coalition of investigators has found that air pollution directly causes cognitive deficits (negatively affects cognition) independently from the reduced lung functioning that accompanies exposure to air pollution.
So, it looks like those of us that complain about not being able to think clearly after breathing in diesel fumes for long periods of time now have some scientific evidence to back us up — if you’re breathing in polluted air, you’re limiting your cognitive abilities, and it’s not just because you’re having trouble breathing.
Until this new work from Swiss + German researchers, it wasn’t quite clear whether air pollution worked to diminish cognitive abilities via the reduction of effective breathing firstly, or whether air pollution was itself a cause of cognitive deficits.
Study leader Mohammad Vossoughi, a PhD student at the Leibniz Institute for Environmental Medicine, commented on the work: “Our findings disprove the hypothesis that air pollution first decreases lung function and this decline, in turn, causes cognitive impairment by releasing stress signals and humoral mediators into the body.”
This work means that other possible mechanisms must now be considered — such as the possibility that that particulate pollution (as well as other forms of pollution) could be “translocated to the central nervous system via our sense of smell.”
Green Car Congress provides a bit more information:
To reach their conclusions, the team of German and Swiss researchers used data from the cohort Study on the influence of Air pollution on Lung function, Inflammation and Aging, or SALIA. The researchers first tested the association between impaired lung function and cognitive impairment. They measured change in lung function through force expiratory volume in one second (FEV1) and forced volume capacity (FVC). They measured cognitive changes using tests from the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD), a neuropsychological battery used to study Alzheimer’s progression.
After adjusting for risk factors known to affect lung and/or cognitive impairment, including age, body mass index, smoking status, education, and the presence of a gene variant implicated in Alzheimer’s disease (the ApoE ε4 risk allele), they found the strongest association between impaired lung function and cognitive decline in the test that measures visuo-spatial ability. At baseline: one liter lower FVC resulted in an absolute decline in cognition of -0.3583 (p=0.007); one liter lower FEV1 resulted in a decline of -0.3075 (p=0.048). This association persisted at follow-up.
Next, the group applied a mediator analysis to test the influence of lung function on the air-pollution-cognitive-decline association. They looked at both particulate matter (PM) and nitrogen dioxide (NO2), factors known to reduce lung health. After studying changes in FEV1 and FVC as a result of an interquartile increase in both from baseline, they could not find a corresponding decrease in visuo-spatial ability: PM10 (β= -0.3158; p < 0.001 to β= -0.3082; p < 0.001); NO2 (from β= -0.3111; p=0.003 to β= -0.3018; p=0.004).
While the researchers consider the next work to be fairly comprehensive, they do state that further enquiry is a given in order to verify the findings — most especially to verify the findings in other demographics (men + the non-elderly). Further is also needed in order to “elucidate the mechanisms underlying impaired lung function, air pollution and cognitive decline.”