Drinking coffee at night may raise impulsivity in women — Study

NEW DELHI — Are you someone who reaches for a cup of coffee every night? According to a new study, nighttime caffeine consumption can increase impulsive behaviour, potentially leading to reckless actions, especially among women.

The findings could have negative implications for shift workers, health care, and military personnel who consume coffee at night, particularly females, said a team of biologists from The University of Texas at El Paso (UTEP).

The study, published in the journal iScience, examined how nighttime caffeine intake affects inhibition and impulsivity in fruit flies.

Drosophila melanogaster, the fruit fly species used in the study, is a powerful model to study complex behaviours due to its genetic and neural parallels with humans.

The team designed a series of experiments introducing caffeine into the flies' diets under various conditions, including different caffeine doses, nighttime versus daytime consumption, and in combination with sleep deprivation.

They then assessed impulsivity by measuring the flies' ability to suppress movement in response to strong airflow -- a naturally unpleasant stimulus.

"Under normal circumstances, flies stop moving when exposed to strong airflow," said Erick Saldes, a science research specialist at the University of Illinois College of Medicine Peoria.

"We found that flies consuming caffeine at night were less able to suppress movement, displaying impulsive behaviours such as reckless flying despite these aversive conditions," Saldes added.

Interestingly, caffeine consumed by the flies during the daytime did not lead to the same reckless flying, the team said.

Further, despite having comparable levels of caffeine in the body, females exhibited significantly greater caffeine-induced impulsivity than males.

"Flies don't have human hormones like oestrogen, suggesting that other genetic or physiological factors are driving the heightened sensitivity in females," said Biological Sciences Professor Kyung-An Han.