BAKU
A new study from the University of Texas at El Paso (UTEP) has found that caffeine consumed at night can increase impulsive behavior particularly in females. Published in the journal iScience, the research was led by UTEP biologists Erick Saldes, Paul Sabandal, and Professor Kyung-An Han.
The team used fruit flies (Drosophila melanogaster) to study how caffeine affects behavior. Fruit flies are commonly used in scientific research because of their genetic similarities to humans. “Caffeine is the most widely used psychoactive substance, with about 85% of adults in the U.S. using it regularly,” said Sabandal. “We wanted to see if certain factors like the time of day or sex—change how caffeine affects behavior.”
Researchers added caffeine to the flies’ diets under various conditions, including different doses, day versus night intake, and sleep deprivation. They then tested impulsivity by seeing how well flies could suppress movement when exposed to strong airflow, something flies normally avoid.
“We found that flies given caffeine at night were less able to stop moving in response to the airflow,” said Saldes. “They behaved more recklessly, even when facing unpleasant conditions.” Interestingly, caffeine had no such effect when consumed during the day.
The researchers also noted that female flies showed much more impulsive behavior than males, even though both had similar levels of caffeine in their systems. Since flies don’t have human hormones like estrogen, scientists believe other biological factors are behind the increased sensitivity in females.
Professor Han said understanding these factors may help explain how nighttime caffeine affects people differently based on sex and body rhythms.
The findings could have real-world implications for shift workers, healthcare professionals, and military personnel who often rely on caffeine at night—especially women. The research was carried out in UTEP’s Department of Biological Sciences, where Han’s lab studies how the brain controls learning, memory, addiction, and other behaviors.
