Daijiworld Media Network - New Delhi

New Delhi, Aug 6: If you're in the habit of grabbing a cup of coffee late at night, you may want to think twice. A new study suggests that caffeine consumption during nighttime hours can heighten impulsive behaviour, with the effect being more pronounced in females.

The research, conducted by a team of biologists from the University of Texas at El Paso (UTEP) and published in the journal iScience, highlights the potential risks of nighttime caffeine intake — especially for individuals in professions like health care, military service, and night shifts, where staying alert is essential.

Using fruit flies (Drosophila melanogaster) — a widely accepted model for studying neurological and behavioural processes — researchers examined how caffeine affects inhibition and impulsivity under different conditions. The flies were given caffeine in varying doses, both during the day and at night, and some were also subjected to sleep deprivation.

To test impulsivity, the team observed the flies' response to strong airflow, a stimulus that typically causes them to stop moving. But those that had consumed caffeine at night behaved differently.

"Under normal circumstances, flies stop moving when exposed to strong airflow," explained Erick Saldes, a research specialist at the University of Illinois College of Medicine Peoria. “But those with nighttime caffeine intake showed impulsive behaviours — flying recklessly, despite the aversive condition.”

Daytime caffeine intake did not trigger the same response, suggesting that timing plays a crucial role in how caffeine affects behaviour.
The study also uncovered a striking gender-based difference: female flies exhibited significantly greater caffeine-induced impulsivity than males, even though both had similar levels of caffeine in their systems.

"Interestingly, flies don't have human hormones like estrogen, so other genetic or physiological mechanisms must be influencing this increased sensitivity in females," said Professor Kyung-An Han, a neuroscientist at UTEP.

She noted that further research into these mechanisms could shed light on sex-specific responses to stimulants and how our circadian rhythms influence behavioural control.

While the study was conducted on fruit flies, the findings raise important questions about nighttime caffeine use in humans, particularly for women and those in high-stakes or safety-sensitive roles. The researchers urge caution and further investigation into how late-night caffeine consumption might affect decision-making and risk-taking in people.