Everyday chemicals linked to cognitive decline in older adults, especially men, new study reports

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Men with higher levels of these chemicals in their bodies were nearly 1.8 times more likely to show cognitive difficulties, especially in immediate word recall and processing speed. (Photo credit: iStock by Getty Images)

Older adults exposed to a mix of chemicals found in everyday products—such as food packaging, cosmetics, and printed receipts—may face a higher risk of memory loss and cognitive decline, according to a study published last month (April 2025) in the Journal of Affective Disorders. 

Using data from nearly 900 U.S. adults with an average age of 69, researchers found that combined exposure to phenols, parabens, and especially phthalates was linked to lower scores on standard tests of brain function, particularly among men.

The more chemicals in participants’ bodies, the worse they performed on tests that measure cognition, such as memory, learning, problem-solving, and attention. But even low levels, as detected in urine samples, were associated with signs of cognitive decline, the researchers say.

Key findings include:

Most chemical safety standards still evaluate substances individually, even though people are exposed to mixtures every day. The study warns that these combined exposures may accumulate and interact in the body. 

This could have stronger, more harmful effects on brain health than single chemicals alone—especially in older adults at a time when aging-related Alzheimer’s and Parkinson’s diseases are common neurodegenerative disorders. According to a 2022 study, nearly one in 10 U.S. adults ages 65 and older has dementia, while another 22% have mild cognitive impairment. 

“Chronic exposure to harmful elements can disrupt neural processes, damaging the brain and causing memory loss,” the researchers say. “Given that older adults are a vulnerable group in terms of health, cognitive decline can severely impact their quality of life and independence.”

Combined chemicals linked to lower cognitive test scores

Phthalates, parabens, and phenols—common in consumer products like plastic containers and shampoos—are known endocrine disruptors. These chemicals interfere with hormone function and have been associated with reproductive issues, developmental delays, obesity, asthma, metabolic dysfunction, cancer, and other severe health problems. Most recently, new evidence emerged that plastic polymers and their chemical additives contribute to cardiovascular disease. 

In 2018, more than 356,238 deaths worldwide were attributed to exposure to DEHP, the most widely used plasticizer or plastic “softener,” representing about 13% of all cardiovascular deaths among individuals aged 55–64. Of these, the vast majority (349,113) were attributed to the use of plastics, according to a study [April 2025] published in the journal eBioMedicine.

Our study suggests that exposure to phenols, parabens, and PAEs may negatively affect cognition in older adults, particularly in the male population.

The researchers analyzed data from 856 people (417 men and 439 women) who participated in the National Health and Nutrition Examination Survey (NHANES) between 2011 and 2014. Urine samples were analyzed for nine chemicals:

Participants also completed four cognitive tests assessing memory, attention, and processing speed:

Researchers then used three types of statistical models to examine the relationship between chemical exposures and cognitive performance. All showed that combined chemical exposures were significantly associated with lower test scores, with the strongest and most consistent declines seen in men.

Of all the chemicals, the phthalate MEHP—a breakdown product of DEHP—had the greatest negative association with cognitive scores, though it may interact with other factors. MEHP is more toxic than DEHP and more easily absorbed by the body, the researchers say.

Prior studies suggest MEHP may contribute to inflammation, a known factor in cognitive decline, and have toxic effects on organs like the liver, testes, pituitary gland, and heart, the researchers say. Prenatal exposure to phthalates may be associated with slower information-processing and lower recognition memory ability in infants, one study shows.

MPB, which is commonly used to prolong shelf life in preserved foods like jams and beverages, showed the highest exposure levels among participants. Higher levels of both MPB and EPB were associated with a lower risk of cognitive problems on certain tests. But these results were inconsistent, the researchers note, and may reflect more complex interactions between chemicals, overall health, and brain function. 

The authors also suggest that biological differences may help explain why older men were more affected by environmental chemicals than women. A prior study showed boys exposed to phthalates before birth scored lower on language tests, while an animal study linked phthalates to anxiety-like behaviors and brain changes in male mice. Gender differences in the brain also make males developmentally vulnerable to neurological disorders, according to another study.

More studies needed on mixed chemical impacts on the brain

Earlier research with 835 NHANES participants indicated that mixed exposure phthalates may be a risk factor for cognitive decline. 

The authors of this study caution that it also does not definitively prove these chemicals directly cause cognitive problems—only that a strong association exists. More research, particularly long-term and focused on men, is needed to confirm these findings and clarify how chemical mixtures affect the brain.

Among other limitations, the study did not adjust for multiple statistical comparisons, which raises the chance of false-positive results, the authors say. It also used data from only two NHANES cycles, which may limit how broadly the findings apply. In addition, health conditions like stroke or smoking history were also self-reported, which can introduce errors, they say.

Reference

Du H, Wang Q, Chen Y, Wu X, Jiang J, Zhao Y. Association between mixed exposure of phenols, parabens, phthalates and cognitive function in US elders. J Affect Disord. Published online April 19, 2025. doi:10.1016/j.jad.2025.04.079