Newswise — San Diego (April 25, 2018)—A new study in medical students finds that summer, not winter, is the season when people are most likely to have higher levels of circulating stress hormones. These non-intuitive findings contradict traditional concepts of the taxing physical toll of winter and the relaxed ease of summer. Researchers will present their findings today at the American Physiological Society (APS) annual meeting at Experimental Biology 2018 in San Diego.

Cortisol—often referred to as the “stress hormone” because it is released into the bloodstream during stressful situations—helps regulate the body’s levels of sugar, salt and fluids. The hormone helps reduce inflammation and is essential for maintaining overall health. Cortisol levels are typically highest in the morning and gradually drop throughout the day. Levels are lower in the evening to maintain healthy sleeping patterns. Illness, lack of sleep and certain medications can affect cortisol levels more than normal daily fluctuations. Researchers from Poznan University of Medical Sciences in Poland have now discovered seasonal patterns in the cortisol levels of medical students.

The research team studied a group of female medical students on two separate days in the winter and for two days again in the summer. The researchers took saliva samples every two hours during each testing period—a full 24-hour cycle—to measure levels of cortisol and markers of inflammation. The volunteers completed a lifestyle questionnaire during each testing session about their sleep schedule, type of diet they followed and physical activity levels.

Previous studies on the seasonal variability of cortisol have shown inconsistent findings—possibly because participants were tested in their own homes and not in a uniform setting. In the current study, however, the research team found cortisol levels to be higher on the summer testing dates. Inflammation levels did not change significantly between seasons.

Dominika Kanikowska, of Poznan University of Medical Sciences, will present the poster “Daily and seasonal rhythms of interleukin 6 and cortisol levels in saliva and some lifestyle habits of medical students in Poland” on Wednesday, April 25, in the Sails Pavilion of the San Diego Convention Center.

NOTE TO JOURNALISTS: To schedule an interview with a member of the research team, please contact the APS Communications Office or 301-634-7209. Find more research highlights in the APS Press Room.

About Experimental Biology 2018

Experimental Biology is an annual meeting comprised of more than 14,000 scientists and exhibitors from five sponsoring societies and multiple guest societies. With a mission to share the newest scientific concepts and research findings shaping clinical advances, the meeting offers an unparalleled opportunity for exchange among scientists from across the United States and the world who represent dozens of scientific areas, from laboratory to translational to clinical research.

About the American Physiological Society (APS)

Physiology is the study of how molecules, cells, tissues and organs function in health and disease. Established in 1887, the American Physiological Society (APS) was the first U.S. society in the biomedical sciences field. The Society represents more than 10,500 members and publishes 15 peer-reviewed journals with a worldwide readership.

Meeting Link: American Physiological Society (APS) annual meeting at Experimental Biology 2018