A study following 400 adults over eight weeks found that a short afternoon nap of around 20 minutes improved attention scores on evening tasks, without measurably affecting participants' night-time sleep quality.

Researchers controlled for caffeine intake and screen time, both known to affect alertness, and said the effect held even after accounting for those factors.

The researchers cautioned that naps longer than 30 minutes showed a smaller benefit and, in some participants, made it harder to fall asleep at night.