Most of us have experienced the "brain fog" that comes after a bad night's sleep. A new study, however, reveals that when it comes to the effect of sleep deprivation on working memory, women fare worse than men.

The term working memory refers to our ability to hold information for short periods of time, at the same time as using it to make decisions or complete tasks.

One example of working memory is adding a contact to your cell phone; you are temporarily storing a string of numbers in your mind while simultaneously tapping them onto your screen.

Previous research found that working memory can be negatively impacted by a lack of sleep.

The researchers behind the new study—led by Frida Rångtell, a PhD student in the Department of Neuroscience at Uppsala University in Sweden—sought to find out more about how a poor night's sleep impacts working memory.

One of the aims of this study was to determine whether lack of sleep affects the working memory of men and women differently, "[given] that sleep-wake regulation and its impact on cognitive performance differs between men and women," the team notes.

Rångtell and colleagues recently reported their findings in the Journal of Sleep Research.

A cause for concern?

The study included a total of 24 young adults, of whom 12 were men and 12 were women. Each subject completed two memory tests 1 week apart.

The first test was taken the morning after a full night's sleep—defined as around 8 hours—while the second test was taken the morning after an entire night of sleep loss.

The memory test required the participants to remember an eight-digit sequence of numbers. Each subject repeated the test 16 times, and the team used their average scores to estimate their working memory performance.

To the researchers' surprise, the results revealed that a night's sleep loss appeared to have no impact on the working memory of men.

Women who lost a night's sleep, however, showed a reduction in working memory in the tests, though they did not appear to notice this reduction.

Rångtell and colleagues say that this result may be a concern for women. "Working memory is central in cognitive functioning and key to perform[ing] efficiently and effectively in academic, professional, and social settings," they write in their paper.

"With this in mind," they add, "it is highly conceivable that a drop in working memory performance due to acute sleep loss represents a risk factor for harmful accidents and mistakes."

As Rångtell points out, women might need to be extra cautious in their day-to-day activities after having a bad night's sleep.

"Our study suggests that particular attention should be paid to young women facing challenges in which they have to cope with both a high working memory load and a lack of sleep."

Frida Rångtell

Speaking of the study limitations, Rångtell notes that it is unclear whether a lack of sleep affects women's working memory throughout the day, as they only tested it during the morning hours.

Additionally, she notes that they are unable to conclude whether the effects of sleep deprivation on other areas of mental activity vary by sex.