Do you drink coffee at night to keep you awake? A new study from the University of Texas at El Paso suggests the habit may have some unexpected downsides. Scientists have found that consuming caffeine at night increases impulsive behavior, making you more likely to engage in risky or uncontrollable behavior.
The survey results are iscienceis from a study led by Dr. Eric Sardes, Dr. Paul Sabandal, and Dr. Kyung-An Han. Researchers used fruit flies to examine how caffeine ingested at different times of the day affects inhibition and impulsivity.
The tree species used are Drosophila melanogasterwhose genetic makeup and nervous system share important similarities with humans, are widely used in behavioral research, Han explained.
“Caffeine is the most widely consumed psychoactive substance in the world, with approximately 85 percent of U.S. adults using caffeine on a regular basis,” said Sabandar, a research assistant professor in the UTEP School of Biological Sciences. “Given the popularity of caffeine, we wanted to investigate whether additional factors influence its effects on behavioral control.”
Caffeine at night leads to decreased self-control
To test this, the research team gave fruit flies caffeine under different conditions, including different doses, daytime and nighttime exposure, and in combination with sleep deprivation. They then assessed impulsivity by observing the extent to which the flies were able to stop moving when exposed to strong air currents, which are inherently uncomfortable for the flies.
“Under normal circumstances, flies stop moving when exposed to strong air currents,” says Sardes, now a scientific research specialist at the University of Illinois at Peoria School of Medicine and a former doctoral student at UTEP. “We found that flies that consume caffeine at night have a reduced ability to inhibit locomotion and exhibit impulsive behaviors such as reckless flight despite such aversive conditions.”
Flies that received caffeine during the day did not show the same pattern, indicating that the timing of caffeine intake plays an important role.
Female flies have a stronger response to caffeine
Researchers also observed clear differences between men and women. Even though both men and women had similar levels of caffeine in their systems, women showed much higher levels of impulsive behavior.
“Flies do not have human hormones like estrogen, which suggests that other genetic or physiological factors are causing the increased susceptibility in females,” said Kyung-an Han, professor of biological sciences. “Uncovering these mechanisms will help us better understand how nighttime physiology and gender-specific factors modulate the effects of caffeine.”
Potential impact on night shift workers
The findings could have broader implications for people who rely on caffeine at night, such as shift workers, medical professionals and military personnel. Researchers note that these effects may be particularly relevant for women.
The research was conducted in Han’s lab in the UTEP School of Biological Sciences. The laboratory focuses on the neurobiological basis of behavioral plasticity, including learning, memory, and addiction, as well as gene-environment interactions associated with Alzheimer’s disease and related dementias.
