Airborne pollutions contributed by cars, factories, power plants, and forest fires, add on to the risk factors for Alzheimer's disease as per a UCSF-led study, published in the journal JAMA Neurology.
Alzheimer's disease (AD) is a neurodegenerative disease that is characterized by a decline in memory and cognition due to the formation of beta-amyloid plaques and tau proteins in the brain tissue - pathological hallmark.
Air pollution remains a threat to various health problems and cardiopulmonary diseases. Existing studies also suggest its implications on cognitive impairment which may lead to dementia - AD in later life. Although air pollution is proposed to alter the amyloid-beta processing, anti-oxidant defense, and inflammatory process in the brain, the underlying mechanism that leads to cognitive problems remain masked.
The researchers enrolled 18,178 participants (Medicare beneficiaries) of average age 75 who were diagnosed with mild cognitive impairment or dementia, for the IDEAS study (Imaging Dementia - Evidence for Amyloid Scanning). PET scans of those who lived in the most polluted areas showed 10 percent increased amyloid plaques depositions in their brain, as compared to those in the least polluted areas. While 40 percent of the participants showed no evidence of plaques on the scan, suggesting non-Alzheimer's diagnoses like frontotemporal or vascular dementias.
Air pollution in the neighborhood of each participant was estimated with Environmental Protection Agency datathat measured ground-level ozone and PM2.5 - fine particles of a diameter of fewer than 2.5 micrometers, produced from burning fuel and chemical reactions that could pose a greater health risk.
"Exposure in our daily lives to PM2.5, even at levels that would be considered normal, could contribute to induce a chronic inflammatory response. Over time, this could impact brain health in a number of ways, including contributing to an accumulation of amyloid plaques", said first author Leonardo Iaccarino, Ph.D., also of the UCSF Memory and Aging Center, Department of Neurology and the Weill Institute of Neurosciences.
When applied to the U.S. population, with an estimated 5.8 million people over 65 with Alzheimer's disease, high exposure to microscopic airborne particles may be implicated in tens of thousands of cases. Due to emerging pieces of evidence, the Lancet Commissionon dementia included air pollution, together with excessive alcohol intake and traumatic brain injury, to their list of risk factors for dementia, in 2020.
The study sheds light on the risk factors of AD due to air pollution, thereby urging the need to modify these elements to prevent cognitive decline.