Many in our society have been appropriately concerned about the burning of fossil fuels because of its impact on our environment in general and on global warming in particular. But the destruction of our planet isn’t the only problem with using fossil fuels; it also causes air pollution which leads to death, cognitive decline and Alzheimer’s disease.
Fossil Fuel Pollution Kills More Than 8 Million People Each Year
A new study from researchers at Harvard University and colleagues in the United Kingdom, published in the journal Environmental Research, estimates that in 2018 pollution from fossil fuel emissions likely caused 18 percent of total global deaths, or more than 8 million people—a staggering number. Countries with the greatest estimated numbers of fossil fuel pollution deaths were China (3.9 million) and India (2.5 million). Another study in China found that there are 1,166 early deaths attributable from air pollution for every 100,000 people ages 75 and older.
How do fossil fuel emissions cause death? As individuals breathe in the polluted air it causes a variety of lung and heart diseases, including lung cancer, chronic obstructive pulmonary disease, emphysema, asthma, heart disease and stroke. I’d love to say that the story ends there, but it doesn’t. In addition to damaging the lungs and heart, air pollution is related to an increased rate of cognitive impairment, dementia and Alzheimer’s disease.
Air Pollution Is Associated With Cognitive Impairment, Dementia and Alzheimer’s Disease
Several studies suggest that air pollution might lead to brain damage. In one study, researchers from China and the United States found that long-term exposure to air pollution was related to poor performance on verbal and math tests, particularly for older individuals and those with less education. A study from England examined 130,978 adults ages 50 to 79 years from 75 medical practices in greater London, finding that that from 2005 to 2013, 1.7 percent of this sample was diagnosed with dementia, with about a third due to Alzheimer’s disease, a third due to vascular dementia, and the remaining third not given a specific dementia diagnosis.
‘Older adults living in areas with the highest annual concentration of air pollution had a higher risk of dementia.’
Importantly, those older adults living in areas with the highest annual concentration of air pollution had a higher risk of dementia compared with those living in areas with lower concentrations of pollution. In addition, the correlation between pollution and Alzheimer’s disease was particularly robust.
Does Air Pollution Shrink Your Brain?
Researchers from the University of Southern California and Harvard Medical School looked at the effect of air pollution not only on cognition but also on brain size. They looked at data from 998 women ages 73 to 87 years and found that women who were exposed to higher concentrations of air pollution in the preceding three years showed both greater declines in learning a list of words as well as more brain atrophy (shrinkage). But what was particularly worrisome was that those areas that shrunk were the same areas as those that typically shrink from Alzheimer’s disease.
This carefully conducted study controlled for multiple possible confounding factors including age, geographic region, race/ethnicity, education, income, smoking history, alcohol history, average physical activity, employment status, diabetes, high cholesterol, hypertension, cardiovascular diseases, hormone therapy and MRI-measured cerebrovascular disease.
How Is Air Pollution Related to Impaired Cognition, Brain Shrinkage and Alzheimer’s Disease?
So how do fossil fuel emissions lead to cognitive impairment, brain atrophy and Alzheimer’s disease? The first thing to note is that correlation is not the same as causation. My favorite example on this point is that just because German researchers found a strong correlation between the decline in the number of storks in Germany and the decline in the German birth rate, does not prove that the lower numbers of births is caused by the lower number of storks. Thus, although air pollution is correlated with cognitive impairment, brain atrophy and Alzheimer’s disease, it may or may not cause them.
The pollution particles may sit around forever as amyloid plaques and inflammatory cells build up around them.
There are, however, many possible mechanisms as to how air pollution might cause Alzheimer’s disease. One possible—but unproven—mechanism is related to a relatively new theory about the normal function of amyloid protein in the brain. Researchers at Massachusetts General Hospital and Harvard Medical school have speculated that the normal function of the beta-amyloid protein is to help the brain fight off infections. If this hypothesis is correct, the explanation may go like this: Some of the particulate matter in fossil fuel emission is just the right size to travel from the lungs, through the blood stream and into the brain. Once in the neural tissue, the brain’s defense mechanisms—including the amyloid system—spring into action trying to “kill” the “invading” particles of pollution.
The particulate matter cannot be killed, and so the pollution particles sit around forever as amyloid plaques and inflammatory cells build up around them. The build-up of amyloid plaques and inflammatory cells leads directly to the formation of tau tangles and destruction of brain cells that is Alzheimer’s disease.
How to Reduce Air Pollution and Lower the Risk of Alzheimer’s Disease and Death?
The researchers from Harvard and the United Kingdom who found that fossil fuel emissions were related to more than 8 million deaths globally made a strong statement of how we can reduce air pollution and lower our risk of death. They note that their study is a “clear message to policymakers and stakeholders to further incentivize a shift to clean sources of energy.”
In turn, I hope that policymakers and stakeholders read this article and are spurred to action. In addition, I hope that readers will elect local and national leaders in your towns, cities, states and countries who will advocate for clean energy.
Lastly, we should all do what we can on our own to reduce fossil fuel emission. We can bike, walk, carpool and take public transportation. We can purchase local produce and other foods that don’t need to be trucked across the country and shipped around the world. And we can reuse and recycle materials to reduce manufacturing in factories. We can make a difference in our health—and the health of our planet.
Andrew E. Budson, MD, is chief of Cognitive & Behavioral Neurology at the Veterans Affairs Boston Healthcare System, professor of Neurology at Boston University, lecturer in neurology at Harvard Medical School, and associate director of the Boston University Alzheimer’s Disease Research Center. His book, “Seven Steps to Managing Your Memory” explains how to distinguish Alzheimer’s from normal aging, what medications, vitamins, diets and exercise regimes can help, and the best strategies and memory aids to use. His latest book, “Six Steps to Managing Alzheimer’s Disease and Dementia: A Guide for Families” teaches caregivers how they can manage all the problems that come with dementia—and still take care of themselves.