“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 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 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.”

See previous sleep research from the Envirome Institute: Reduced sleep linked to environmental factors | UofL News.

The Nature Conservancy is overseeing the planting of approximately 8,000 trees and shrubs in the designated neighborhoods. Researchers with the University of Louisville’s Christina Lee Brown Envirome Institute will compare data about the health of people living in the neighborhoods and air pollution levels collected before the plantings with data collected two years after the vegetation is planted. The results will provide insight into how the additional vegetation affects the health of people in the community.

“Our primary objective is to understand how increasing greenness affects the risk of heart disease within the community,” said Aruni Bhatnagar, PhD, director of the at the University of Louisville, who oversees the project. “Heart disease remains the leading cause of death throughout the world. We can treat heart disease with stents and statins, but we cannot prevent the disease. If we can show that putting in more trees will lower the incidence of the disease, even by a fraction of what it is, that would be a major achievement.”

The Nature Conservancy is planting the trees and shrubs in designated residents’ yards at no charge to property owners.

“We’re excited to enter the next phase of the Green Heart project,” said David Phemister, state director for in Kentucky. “Tree plantings at this scale require strong partnerships and deep engagement with the community. Green Heart is not just a science experiment – it is a deep investment to bring more nature to neighborhoods in the heart of Louisville.”

The residents’ health is being assessed by UofL researchers through the Health, Environment and Action in Louisville (HEAL) Study. The HEAL researchers obtained health information from approximately 700 participating residents of the Taylor-Berry, Jacobs, Hazelwood, Oakdale, Wilder Park and Beechmont neighborhoods before the planting began. They collected information such as blood pressure, cholesterol, heart health and other health indicators. The same participants will be evaluated again in two years to determine if these health indicators have changed.

“We wanted Louisville to become maybe one of the first cities in the country that makes its decisions through the lens of all forms of health,” said Christina Lee Brown, benefactor of the Envirome Institute. “That is the Envirome’s objective. This project is a magnificent example of healing our community from the roots up.”

In addition to the Envirome Institute and The Nature Conservancy, the project is funded by the National Institutes of Health and is supported by partnerships with Metro Louisville, Louisville Grows, Washington University in St. Louis, Hyphae Design Laboratory and the United States Forest Service. The total cost of the five-year project is more than $15 million.

A UofL video about this project is available on .

In this study, the first of its kind, researchers from the University of Louisville investigated the impact of neighborhood greenspaces on individual-level markers of stress and cardiovascular disease risk.

Over five years, blood and urine samples were collected from 408 people of varying ages, ethnicities and socioeconomic levels, then assessed for biomarkers of blood vessel injury and the risk of having cardiovascular disease. The participants were recruited from the and were largely at elevated risk for developing cardiovascular diseases.

The density of the greenspaces near the participants’ residences were measured using the Normalized Difference Vegetation Index (NDVI), a tool that indicates levels of vegetation density created from satellite imagery collected by NASA and USGS. Air pollution levels also were assessed using particulate matter from the EPA and roadway exposure measurements.

Researchers found living in areas with more green vegetation was associated with:

• Lower urinary levels of epinephrine, indicating lower levels of stress;
• Lower urinary levels of F2-isoprostane, indicating better health (less oxidative stress);
• Higher capacity to repair blood vessels.

They also found that associations with epinephrine were stronger among women, study participants not taking beta-blockers – which reduce the heart’s workload and lower blood pressure – and people who had not previously had a heart attack.

“Our study shows that living in a neighborhood dense with trees, bushes and other green vegetation may be good for the health of your heart and blood vessels,” said Aruni Bhatnagar, PhD, lead study author and professor of medicine and director of the UofL and the . “Indeed, increasing the amount of vegetation in a neighborhood may be an unrecognized environmental influence on cardiovascular health and a potentially significant public health intervention.”

The findings were independent of age, sex, ethnicity, smoking status, neighborhood deprivation, use of statin medications and roadway exposure.

Previous studies also have suggested that neighborhood greenspaces are associated with positive effects on overall physical and psychosocial health and well-being, as well as reduced rates of death from cardiovascular and respiratory diseases and improved rates of stroke survival, according to Bhatnagar. However, these reports are largely limited by their reliance on self-reported questionnaires and area-level records and evaluations, Bhatnagar said.

Co-authors of this study are Ray Yeager, Ph.D.; Daniel W. Riggs, M.S.; Natasha DeJarnett, Ph.D.; David J. Tollerud, Ph.D.; Jeffrey Wilson, Ph.D.; Daniel J. Conklin, Ph.D.; Timothy E. O’Toole, Ph.D.; James McCracken, Ph.D.; Pawel Lorkiewicz, Ph.D.; Xie Zhengzhi, Ph.D.; Nagma Zafar, M.D., Ph.D.; Sathya S. Krishnasamy, M.D.; Sanjay Srivastava, Ph.D.; Jordan Finch, M.S.; Rachel J. Keith, Ph.D.; Andrew DeFilippis, M.D.;  Shesh N. Rai, Ph.D. and Gilbert Liu, M.D. Author disclosures are on the manuscript.

The WellPoint Foundation and the National Institute of Environmental Health Sciences of the National Institutes of Health supported the study. View the manuscript .