“From the beginning, this has been an incredibly productive collaboration between our research groups and respective departments,” Witman said. “Elissa was very successful throughout her Ph.D. and postdoctoral training at UD, and her work is a great example of the interdisciplinary opportunities that exist in the College of Health Sciences.” 

Witman also highlighted the scientific findings of this collaborative and impactful research. 

“As we objectively assess various behaviors in participants and clinically meaningful indices of cardiovascular health, we are also identifying these associations in young adults before they have developed or been diagnosed with any known cardiovascular disease,” Witman said. “This is particularly exciting as these behaviors are modifiable. These findings have big implications as we work towards different strategies to delay or prevent the development of cardiovascular disease.”  

While sleep and circadian rhythms are often thought of in tandem, the timing of eating may be equally as crucial to healthy circadian rhythms and, in turn, cardiovascular health.

Those potential associations inspired a follow-up study in which Hoopes worked closely with Patterson, her postdoctoral mentor and senior author of the JAHA article. They expanded the age range of study participants from 18 to 45 to ensure study results were more generalizable to early adulthood. They also used a different measure of blood vessel health: the thickness of the carotid artery. This is because atherosclerosis causes gradual thickening of the arteries due to a buildup of plaque over time. So, measuring artery thickness can provide insight into atherosclerosis development, even in very early stages.

Using a cellphone app, researchers asked participants to photograph everything they ate and drank daily for over two weeks. From there, researchers analyzed what they were eating, how much food was being consumed, the quality of the food, and what time they were eating, including the time they took their first and last bites each day. 

They then looked closely at day-to-day variability in three critical measures of eating timing — eating onset, eating offset and caloric midpoint. Variability in eating onset and eating offset indicates the extent to which someone exhibits irregularity in the first and last times they eat each day. On the other hand, variability in the caloric midpoint, or the time at which 50% of all calories for the day have been consumed, indicates the extent of irregularity in the placement of calories across the 24-hour day. 

“Caloric midpoint variability was the measure most strongly associated with carotid artery thickness,” Hoopes said. “Variability in eating onset/offset wasn’t as significant. It didn’t matter if people were consistent when they had their first or last bite each day. It mattered more whether they were consistent with when they ate their calories over the course of the day. 

“If they consistently consumed a lot of calories in the morning and less at night or consumed a lot of calories at night and less in the morning — so long as they were consistent in those behaviors — they had better vascular health compared to those who had a big breakfast one day and a big dinner the next day. This high day-to-day variability in the placement of calories across the 24-hour day was negatively associated with vascular health.” 

Like their first sleep variability study, the follow-up study again found that irregular sleep schedules — specifically, high night-to-night variability in sleep duration — was also associated with poorer vascular health. This time, though, poorer vascular health meant thicker arteries.

“The message here is that consistency in sleeping and eating behaviors is key,” Hoopes said. “Focus on how much sleep you’re consistently getting. Similarly, focus on the time of day you’re eating and try to eat the same amount around the same time every day. Our research suggests that this consistency may be important to overall cardiovascular health.” 

In addition to Hoopes, Patterson and Witman, co-authors of this interdisciplinary research include Dave Edwards, professor and chair of the KAAP Department; Shannon Robson, associate professor of HBNS; Benjamin Brewer, a biostatistician with the Epidemiology Program; Michele D’Agata, a doctoral candidate in applied physiology; Thomas Keiser, a doctoral student in HBNS; and Susan Malone, assistant professor at New York University Rory Meyers College of Nursing.