Findings by University of Montana Professor Dr. Lilian Calderón-Garcidueñas and her team of researchers reveal that children with lifetime exposures to concentrations of air pollutants above the current US standards, including fine particulate matter, are at an increased risk for brain inflammation and neurodegenerative changes, including Alzheimer’s and Parkinson’s diseases.

The study found that clinically healthy children who live in a polluted environment and who also carry a gene—the apolipoprotein ε4 allele, already known to increase a person’s risk of developing Alzheimer’s disease—demonstrated compromised cognitive responses when compared with children carrying a gene with apolipoprotein ε3 allele.

Metropolitan Mexico City is an example of extreme urban growth and serious environmental pollution, where 8 million children are involuntarily exposed to harmful concentrations of fine particulate matter in the air every day beginning at conception.

The study matched two groups of children living in Mexico City by multiple variables, including age, gender, socioeconomic status and education, among others. They then compared children carrying the ε4 allele to children carrying the ε3 allele and found that those with the ε4 allele had three significant alterations. They had short-term memory shortfalls, an IQ that while within the normal limits measured 10 points less, and changes in key metabolites in the brain that mirror those of people with Alzheimer's disease.

The results add to growing data suggesting ε4 carriers could have a higher risk of developing early Alzheimer’s disease if they reside in a polluted urban environment.

—Lilian Calderón-Garcidueñas

Calderón-Garcidueñas said the study also raises concerns about important educational issues. Since Mexico City children mostly attend underprovided public schools, children do not build cognitive reserves that serve as a defense to pollution impacts.

The authors argue that sustained exposures to urban air pollution result in cognitive underperformance and metabolic brain changes that could lead to an acceleration of neurodegenerative changes.

Air pollution is a serious public health issue, and exposures to concentrations of air pollutants at or above the current standards have been linked to neuroinflammation and neuropathology. In the US, 200 million people live in areas where pollutants such as ozone and fine particulate matter exceed the standards.

There are significant associations between exposures to particulate matter and increased mortality due to stroke, cardiovascular disease and respiratory events. The problem in children living in megacities like Mexico City is much worse, according to the researchers.

There is an urgent need to have a broader focus on APOE ε4 and air pollution interactions impacting children’s brains, and their responses could provide new avenues toward the unprecedented opportunity for Alzheimer’s disease prevention. We have a 50-year window of opportunity between the time urban children experience the detrimental effects we are describing here and when they will present with mild cognitive impairment and dementia. We need support for studying the current pediatric clinical and imaging evidence in highly exposed urban children. Our efforts should be aimed to identify and mitigate environmental factors influencing Alzheimer’s disease.

—Lilian Calderón-Garcidueñas

Resources

• Lilian Calderón-Garcidueñas, Antonieta Mora-Tiscareño, Maricela Franco-Lira, Hongtu Zhu, Zhaohua Lu, Edelmira Solorio, Ricardo Torres-Jardón, Amedeo D’Angiulli (2015) “Decreases in Short Term Memory, IQ, and Altered Brain Metabolic Ratios in Urban Apolipoprotein ε4 Children Exposed to Air Pollution” Journal of Alzheimer’s Disease doi: 10.3233/JAD-142685