Forever Chemicals: The Link Between PFAS and Dementia
Summary
- The Miller School’s Dr. Hannah Gardener is studying the impact of PFAS on brain health.
- Dr. Gardener and team published a literature review in Alzheimer’s and Dementia highlighting the gap in knowledge regarding how exposure to PFAS in adulthood affects cognition and dementia risk.
- In an upcoming study, Dr. Gardener will follow Northern Manhattan Study participants to determine the relationship between PFAS exposure and cognitive health.
Hannah Gardener, Sc.D., an epidemiologist and research assistant professor in neurology at the University of Miami Miller School of Medicine, has been thinking about studying the effect of per- and polyfluoroalkyl substances (PFAS) on dementia risk for a decade.
“I’ve been really passionate about the impacts of environmental toxicants, plastic exposures and, in particular, PFAS on brain health for over 15 years now,” said Dr. Gardener.
PFAS, also known as “forever chemicals,” have been a popular topic for the past decade. But existing research has focused primarily on impacts of the chemicals on early development.
“The health effects of PFAS exposure on multiple cancers, liver damage, reproduction, immune function, cardiometabolic disease and infant development have been well-evidenced, but there’s not a lot known about the impacts of PFAS on adult brain health,” she said. “The attention has been focused primarily on neurodevelopment and brain health in infants and children, and very little on how adult PFAS exposure impacts adult brains, especially cognitive changes late in life.”
Dr. Gardener and her team published a literature review in Alzheimer’s and Dementia describing the existing research and highlighting the gap in knowledge regarding how exposure to PFAS in adulthood affects cognition and dementia risk. She also laid out her plans, supported by a five-year grant from the National Institutes on Aging, to tease apart the influence of PFAS exposure later in life on cognitive health.
PFAS and Health
PFAS were first produced about 70 years ago. Manufacturers used them to make a wide range of products water- and stain-resistant. Scientists have found that these chemicals persist in the environment—in water, soil, and air, for example—forever. The chemicals can get into people’s bodies when they touch them, drink contaminated water, eat contaminated food or breath contaminated air. PFAS accumulate in our bodies and persist in our organs for decades after exposure, and can wreak havoc on our organs and our health. High PFAS exposure is linked to conditions such as cancer and hormonal disorders.
National Health and Nutrition Examination Survey (NHANES) data have suggested that every person in the U.S. likely has some level of PFAS in his or her blood.
Still, there are only a handful of existing studies on PFAS exposure and dementia. Those studies have produced confusing and conflicting results, Dr. Gardener explained. Surprisingly, some have even suggested that PFAS exposure was correlated with improved cognitive function.
“Those results are hard to trust. There haven’t been any methodologically rigorous epidemiological studies on PFAS exposure and future risk of dementia,” she said.
For example, most studies failed to account for important, confounding factors, including diet and kidney function. Fish often contain PFAS, but also contains compounds that support brain health, such as Omega-3s. That means someone who eats a lot of fish might have a higher PFAS exposure, but also better overall brain health.
“When we fail to account for fish consumption, we increase the risk of making spurious conclusions, and exaggerating the brain health benefits of toxic contaminants found in fish, including PFAS,” she said.
Studying PFAS and Cognitive Function
In the upcoming study, Dr. Gardener plans to follow participants in the Northern Manhattan Study. The cohort is made up of people who were older than 40 between 1993 and 2001 and living in New York City. The group is unique for several reasons. The sample is made up of a diverse group of ethnicities. Most were not exposed to PFAS as children and only became heavily exposed in adulthood. That can help researchers to determine the specific effects of PFAS exposure later in life.
Dementia and Alzheimer’s disease are such substantial and growing public health burdens, and PFAS exposure is something that we can reduce, both at the individual level with lifestyle changes and at the community level with regulatory changes.
Dr. Hannah Gardener
In addition to clarifying the significance of PFAS exposure in dementia risk, Dr. Gardener and her team hope to learn more about how the chemicals exert their effects. Knowing that PFAS exposure is already linked to higher cholesterol in the blood, which is also linked to cognitive decline, Dr. Gardener and her team suspect that PFAS disrupt lipid metabolism and increase atherosclerosis, leading to impaired cognitive function. They’ll also look for differences in outcomes between patients who do and don’t have a common genetic risk factor.
The researchers have taken two blood samples from each participant about six years apart. They will measure the concentrations of 13 different PFAS to determine the individual’s overall PFAS burden and whether it is changing over time. The participants have also had repeated cognitive testing over time and have been evaluated for dementia and mild cognitive impairment. The investigators will examine whether the body burden of PFAS impacts changes in cognitive functioning as well as the risk of dementia.
“This is a big gap in the literature that is important to fill, especially because dementia and Alzheimer’s disease are such substantial and growing public health burdens, and PFAS exposure is something that we can reduce, both at the individual level with lifestyle changes and at the community level with regulatory changes,” said Dr. Gardener. “We really need to identify new avenues for protecting brain health and reducing dementia risk. This study has the potential to elucidate the relationship between a ubiquitous environmental exposure and how it impacts cognitive health, which can then inform future interventions.”
Tags: Alzheimer's disease, brain health, cognitive decline, dementia, Dr. Hannah Gardener, neurology, neuroscience