Nighttime Coffee Linked to Increased Impulsivity in Women: Study Finds
New Delhi: If you often reach for a cup of coffee late at night, you may want to reconsider. A new study by researchers at The University of Texas at El Paso (UTEP) has found that consuming caffeine during nighttime hours may increase impulsive behavior—particularly in females.
Published in the journal iScience, the study explored how nighttime caffeine intake affects inhibition and impulsivity using fruit flies (Drosophila melanogaster) as a model. Though small, these flies are widely used in research due to their genetic and neurological similarities to humans.
The researchers introduced caffeine into the flies’ diets under a variety of conditions, including different doses, timing (day vs. night), and combinations with sleep deprivation. They then assessed the flies' responses to a strong, aversive airflow—a stimulus that usually causes them to stop moving.
“Under normal circumstances, flies stop moving when exposed to strong airflow,” explained 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.”
Interestingly, caffeine consumed during the daytime did not lead to the same behavior, even though overall caffeine levels in the body were similar. The researchers also found that female flies showed a much stronger impulsive response to nighttime caffeine intake than male flies, despite the absence of human hormones like estrogen.
“Flies don’t have human hormones like oestrogen, suggesting that other genetic or physiological factors are driving the heightened sensitivity in females,” said Professor Kyung-An Han from UTEP’s Department of Biological Sciences.
"Uncovering these mechanisms will help us better understand how nighttime physiology and sex-specific factors modulate caffeine's effects," Han added.
This research could have important implications for night shift workers, healthcare professionals, and military personnel—groups that commonly rely on caffeine to stay alert during overnight hours. The findings suggest that consuming caffeine at night could impair judgment or increase risky behavior, especially in women.
As researchers continue to study the underlying mechanisms, the message is clear: when it comes to caffeine, timing—and gender—might matter more than we think.
Dr Bhumika Maikhuri is a Consultant Orthodontist at Sanjeevan Hospital, Delhi. She is also working as a Correspondent and a Medical Writer at Medical Dialogues. She completed her BDS from Dr D Y patil dental college and MDS from Kalinga institute of dental sciences. Apart from dentistry, she has a strong research and scientific writing acumen. At Medical Dialogues, She focusses on medical news, dental news, dental FAQ and medical writing etc.