UofL researcher connecting the dots between pollution exposure in infancy and sleep health in adolescence

Clara Sears is fascinated by sleep. Quality sleep is essential to support growth and development and many adolescents in the U.S. are not getting enough.

“Everyone sleeps and it’s fascinating to me. We know so little about sleep scientifically that it really piqued my interest, and my project is right at the intersection of cardiovascular health and neurodevelopment, so it is kind of the perfect niche for my interest,” said Sears, assistant professor of environmental medicine, a researcher in the University of Louisville’s Christina Lee Brown Envirome Institute and a UofL alumna.

Sears is leading a project to discover how exposure to mixtures of common chemicals and pollutants during gestation and infancy affects sleep health in adolescence. Ultimately, she believes the exposures may be linked to cardiovascular issues later in life. Her work is part of research at the Envirome Institute to understand the relationships between the environment and human health.

“Sleep is increasingly recognized to be central to cardiovascular health. We know that a variety of lifestyle choices and environmental factors affect sleep, but we know little about the effects of chemical exposure and pollutants,” said Aruni Bhatnagar, professor of medicine and director the Envirome Institute. “Clara's work could provide new knowledge about factors that affect sleep, particularly in adolescents, so that we can improve their quality of sleep and future cardiovascular health.”

Sears’ team is examining exposure to combinations of phthalates (common components of plastics), metals and per-/polyfluoroalkyl substances (PFAS – known as “forever chemicals”). People are frequently exposed to these toxicants through their diet, as well as use of consumer goods and household products. Sears said they chose to study mixtures rather than individual chemicals because most people in the U.S. are exposed to them in combination.

“We know pregnant women and children are exposed to these chemicals in mixtures and sometimes they can affect similar biological pathways, or they can interact in ways that may magnify an effect on a health outcome,” Sears said. “So, if we study them in isolation, it is hard to get the real-world relevance of how they interact with each other to affect health.”

The work is funded by a five-year, $2.1 million grant from the National Institutes of Health to determine whether there are connections between these early exposures and poor sleep quality and increases in allostatic load in adolescents. Allostatic load is the cumulative burden of “wear and tear” on the body resulting from stressors that eventually can disrupt an individual’s immune, cardiovascular and metabolic functions. A person’s allostatic load can be assessed through biomarkers and other measures such as inflammation and body composition.

Sears is working with experts in pediatric environmental health, sleep and cardiometabolic health to analyze data from two long-term studies that track prenatal and early life exposures and other health information. The Health Outcomes and Measures of the Environment Study and the Maternal-Infant Research on Environmental Chemicals Study have documented exposures and other health measures in more than 550 children from before birth through pre-teen and teen years, along with sleep health in adolescence.

Sears hopes the study will lead to understanding the link between early life environmental factors and cardiovascular health later in life, informing efforts to improve the environment for infants and children so that they can be healthier into adulthood.

“Sleep impacts every aspect of your health and your day-to-day functioning, so if we can find ways to improve sleep it can have huge impacts on health overall.”