Research

Hazed and confused: New research reveals link between air pollution and dementia

A first-of-its-kind study by health care economists reveals another troubling concern about breathing smoke and dust in the atmosphere: long-term exposure to certain pollutants increases our risk of developing Alzheimer's disease.

By Susie Steckner

2018-09-26

A study by ASU economists — the first of its kind — reveals a new and troubling concern about the air we breathe: long-term exposure to certain pollutants increases our risk of developing dementia.

And this comes at a considerable cost. In addition to increasing Medicare’s costs associated with Alzheimer’s disease, the study finds that dementia impairs people’s ability to make sound financial decisions.

“Dementia is a terrible illness. It disrupts relationships, makes daily life difficult, and leads to death,” says co-author Jonathan Ketcham, the Earl G. and Gladys C. Davis Distinguished Research Professor in Business. “Because it’s so prevalent, it also affects so many of us as family members and caretakers, and it can make us anxious as we consider our old age.

“Unfortunately, medical research has not developed a prevention or cure for dementia, so it has felt like high rates of dementia are inevitable,” he says. “But our results suggest that it is not, and something can be done: reducing the amount of small particulates in the air will reduce the risk of dementia.”

The research also underscores the benefits of clean air.

“Our work shows that those benefits, and the value of regulation and technological innovation that help us clean the air, are even greater than we knew before,” Ketcham explains.

“Hazed and Confused: The Effect of Air Pollution on Dementia,” by health care economist Ketcham, Assistant Professor of Economics Kelly Bishop, and Associate Professor of Economics Nicolai Kuminoff, represents the first large-scale national study of how long-term exposure to air pollution, specifically fine particulate air pollution (or PM2.5), is linked to dementia.

The work offers several critical considerations for policymakers, but one, in particular, stands out.

Researchers estimate that enforcement of the EPA’s 1997 standard on PM2.5 concentrations led to air quality improvements in newly regulated counties, which in turn averted roughly 140,000 people living with dementia in 2013.

A new tool in the arsenal

Researchers have previously found that air pollution causes heart and lung disease that kills people, especially young children and older adults.

But high pollution impacts us in more subtle ways, too, Kuminoff says.

“For example, more polluted air causes people to do worse on cognitive tests, causes agricultural workers to be less productive, and causes baseball umpires to make even more mistakes than usual,” he says. “The smallest particulates mostly cause air pollution's negative effects on cognition — PM2.5 — which means smaller than 2.5 microns or about 1/40th the diameter of a human hair.”

And that’s where the dementia link comes in.

Because of its small size, PM2.5 remains airborne for long periods and can penetrate buildings, is easily inhaled, and can reach and accumulate within brain tissue. That accumulation of particulates in the brain can cause neuroinflammation, which is associated with symptoms of dementia.

To date, policy discussions surrounding dementia have focused on investing in research and health infrastructure, as well as modifying behaviors related to smoking, diet, and exercise. But through “Hazed and Confused,” policymakers have another tool in reducing the prevalence of dementia.

Collaborative environment

A dog sparked the very early work in this arena, Ketcham says. About 15 years ago, a researcher noticed that dogs living in the most polluted parts of Mexico City were showing signs of dementia.

A series of medical studies followed, using mice and human cadavers and small groups of people. Kuminoff was aware of the hypothesis that small air pollution particles might cause dementia.

Ketcham says, “The fantastic collaborative environment here at W. P. Carey led the three of us to combine our data and our expertise.”

Their work came together over the course of three years.

The researchers relied on 15 years of Medicare records for nearly 7 million American adults ages 65 and older to track patients’ dementia diagnoses. At the same time, they used data from the U.S. Environmental Protection Agency showing patients’ cumulative exposure to PM2.5.

Basing their research on the trove of medical records was essential to the finding that 140,000 cases of dementia were averted, Bishop says.

“In contrast to the powerful motivating evidence that came out of the medical literature, our study does not rely on small selected groups of people or animal studies,” she says. “We analyze data describing millions of representative Americans on Medicare.”

Added social costs

As researchers linked air pollution and dementia, they also examined the social costs of this connection.

“Dementia is irreversible and has huge costs for society,” Kuminoff says. “For example, Alzheimer’s patients will spend over a quarter trillion dollars on health care in 2018, according to the Alzheimer’s Association, and taxpayers will cover most of this bill through Medicare.”

Beyond that, the researchers found that dementia negatively impacts a patient’s financial decision making, such as whether to shop around for a prescription drug insurance plan with lower costs.

Now consider the 140,000 dementia cases that were averted because of improved air quality and resulting cost benefits.

According to the study, “Our estimates for the monetary benefits of dementia cases avoided ($163 billion) are sufficiently large to suggest that dementia-related benefits may matter for future benefit-cost analyses of federal air-quality regulations.”

On the horizon

Bishop says the research offers several essential takeaways for policymakers as well as individuals, including:

• When the EPA implemented the new air quality standard in new counties, the benefits were much more significant than previously known with so many dementia cases averted.
• There is potential room for improvement going forward. Lowering the federal cap on fine-particulate air pollution would be useful in further reducing dementia among older Americans.
• The research proposes a pathway to lower one’s own risk of dementia by limiting exposure to fine particulates. This could impact where a person chooses to live or whether a person limits outdoor activity on high-pollution days.

In the United States, air quality has improved steadily due to stricter regulations and technological innovations, Ketcham says.

Supporting policies that will continue to improve air quality and promote innovation is critical.

“This includes federal and local environmental regulations, and also strong capital markets, effective intellectual property protections, vigorous competition, and high-quality education and health care —everything people need to have the opportunities, abilities, and incentives to do the hard work and take risks needed to make great discoveries,” Ketcham says. “Given our results and others’ work showing that clean air improves test performance, job productivity, and cognition in general, cleaner air may be part of a virtuous cycle that helps us accomplish that.”

Environmental Economics