A new study by researchers from the Karolinska Institute, published in Sleep Advances, has revealed an intriguing contradiction: women are significantly more likely than men to report poor sleep, even though objective measurements suggest the opposite.

The study included 476 Swedish adults aged 29 to 85, with equal numbers of men and women. Participants underwent overnight polysomnography, a technique that records brain activity, breathing patterns, and body movements during sleep. The following morning, they were asked to assess their sleep quality.

The findings were surprising. Although women reported poorer sleep more frequently, sleep recordings showed that, on average, they slept better than men across nearly all major indicators.

Women experienced fewer nighttime awakenings, slept longer, spent more time in deep sleep, and used their time in bed more efficiently. In other words, from a physiological perspective, their sleep quality was superior.

The researchers identified a possible explanation for this paradox.

Women appeared to remember their nighttime awakenings much more accurately than men. Men, by contrast, often failed to notice or recall brief periods of wakefulness.

For example, when a man woke up for a few seconds or minutes during the night, he typically still considered that he had slept well. Women, however, were more likely to notice even short awakenings and factor them into their assessment of sleep quality.

When researchers excluded men who experienced these brief, barely noticeable awakenings from the analysis, the differences in subjective sleep ratings between men and women largely disappeared.

According to the study’s lead author, Professor Torbjörn Åkerstedt, men’s more positive perception of their sleep may stem from their reduced awareness or memory of short nighttime awakenings. The reasons behind this sex difference remain unclear.

The study also found that the gap becomes more pronounced with age. Older men showed a greater decline in deep sleep and experienced more frequent nighttime awakenings. Although women also experienced age-related changes in sleep, these changes were less severe. Nevertheless, even in older age, women continued to rate their sleep quality more negatively than men.