Scientists link ‘forever chemicals’ to poor sleep in young adults

Exposure to certain types of “forever chemicals” may be disrupting the sleep quality of young adults — contributing not only to tiredness, but also to potential knock-on health effects, new research has found.

Individuals who had heightened levels of four specific types of per- and polyfluoroalkyl substances (PFAS) in their blood experienced worse sleep, according to the results of a University of Southern California study published in Environmental Advances.

These forever chemicals may be interfering with the function of a gene that is critical to the production of the hormone cortisol, which helps regulate sleep and wakefulness rhythms, the authors noted.

“Because the body needs sleep every day, if PFAS might be interfering with your sleep, that may affect you more immediately than other chronic health issues,” said lead author Shiwen (Sherlock) Li, a postdoctoral researcher at USC’s Keck School of Medicine, in a statement.

There are thousands of types of PFAS, some of which are known to cause illnesses like kidney cancer, testicular cancer and thyroid disease.

Notorious for their ability to persist in the body and the environment, these chemicals are found in certain firefighting foams and industrial waste, as well as in numerous household products, cosmetics and waterproof apparel.

Building upon existing knowledge that PFAS can disrupt hormone and immune function, the researchers collected blood samples and sleep information from 144 people ages 19 to 24. These young adults were participants in the broader USC Children’s Health Study, a long-term effort to research the impacts of pollutants on children.

The scientists gathered their data in two stages — from 136 young adults recruited between 2014 and 2018 and from 76 who were reassessed between 2020 and 2022. An additional eight individuals participated only in the latter window, according to the study.

In each stage, the scientists measured blood concentrations of seven types of PFAS: PFOS, PFOA, PFHxS, PFHpS, PFPeS, PFNA and PFDA. They assessed sleep duration from participant self-reports at both visits, while also tracking sleep disturbance with validated instruments, per the study.

Four of the PFAS evaluated — PFDA, PFHxS, PFOA and PFOS — exhibited significant associations with less sleep or worse quality of sleep for four compounds, the scientists found.

Although PFOA and PFOS are considered “legacy PFAS” and have largely been phased out of production, they remain plentiful and persistent in the environment. 

“It could be a matter of cumulative exposure over time,” Li said. “What we measured in the blood is likely driven by exposure since birth, or even prenatal exposures.”

The researchers found that PFDA, PFOA and PFHxS were connected to shorter sleep duration: young adults with blood levels of these compounds in the highest third slept about 80 minutes fewer each night than those whose levels were in the lowest third.

Meanwhile, PFOS was associated with greater sleep disturbance and sleep-related impairment, with affected participants self-reporting whether they had difficulty falling asleep or staying asleep, or if they had trouble waking up or experienced tiredness during the day.

The scientists then took their findings one step further, in an attempt to divulge just why these chemicals might be contributing to sleep quality.

Seeking out an overlap between potential genes affected by these four PFAS and those related to sleep disorders, they turned to toxicology databases that connect chemicals, diseases and shifts in gene expression.

The researchers then measured participant blood levels of specific proteins that indicate the expression of those suspect genes. Out of more than 600 candidate genes, they found that seven activated by PFAS seemed to affect sleep.

One immune-oriented gene, HSD11B1, contributes to the production of the hormone cortisol, which plays a critical role in controlling sleep and wakefulness patterns, the authors noted.

“If the expression of the protein encoded by HSD11B1 is disrupted, that means that cortisol levels could also be disrupted,” Li said. “That, in turn, affects sleep.”

Another gene, cathepsin B, produces enzymes that serve as a precursor for amyloid beta proteins, which are found in the plaques and brains of Alzheimer’s patients, according to the study. High levels of those enzymes have previously been linked to cognitive decline in Alzheimer’s, which itself has connections to sleep deficits, the researchers explained.

Going forward, the investigators said they plan to continue exploring the impacts of forever chemicals on children’s sleep patterns as part of a broader National Institutes of Health initiative.

“Sleep quality is an issue that affects almost everybody, so the impact of PFAS on sleep may have policy implications,” Li added.