Nighttime Coffee Consumption Linked to Increased Impulsivity, Especially in Women

Recent research from the University of Texas at El Paso reveals that drinking coffee during nighttime hours may significantly elevate impulsive behaviors, with women showing a greater susceptibility. The study, published in iScience, investigated how caffeine intake at night influences inhibition and impulse control using fruit flies as a model organism. Fruit flies, specifically Drosophila melanogaster, serve as excellent models for understanding complex neural and genetic behaviors relevant to humans.

Led by researchers Erick Saldes, Ph.D., Paul Sabandal, Ph.D., and Kyung-An Han, Ph.D., the team experimented with various doses of caffeine introduced into the flies' diets during different times—day versus night—and in conditions of sleep deprivation. They assessed impulsivity by measuring the flies' ability to halt movement in response to a strong airflow stimulus, an instinctive aversive response.

Findings indicated that flies consuming caffeine at night exhibited a marked reduction in their ability to suppress movement, displaying reckless behaviors and impulsivity, unlike those that consumed caffeine during daylight. Interestingly, this effect was not observed in flies that ingested caffeine during the day, underscoring the impact of circadian timing.

A notable sex difference emerged as well: female flies showed significantly higher impulsivity after nighttime caffeine intake even with similar caffeine levels as males. This suggests that physiological or genetic factors beyond hormones like estrogen may influence heightened sensitivity in females.

This study highlights potential risks for shift workers, healthcare professionals, and military personnel who consume caffeine late at night, especially women. The researchers emphasize the importance of understanding how circadian and sex-specific factors modulate the behavioral effects of caffeine.

The findings contribute to the broader understanding of how sitting behaviors and brain functions are affected by environmental factors and biological differences. Future research aims to uncover the underlying mechanisms driving the increased female sensitivity and explore implications for human health and safety.