“Duration is very important,” says Damien Léger, a doctor who runs the sleep-research center at the Hôtel-Dieu hospital in Paris. Aim to sleep for 20 minutes. Anything longer, and you risk drifting into what scientists call slow-wave sleep, a state of languid brain-wave activity considered important for consolidating memories. Set an alarm clock. A slow-wave encounter is likely to leave you with what Léger calls “sleep drunkenness” instead of a feeling of rejuvenation.
Think of napping as a basic right, not a petty luxury. For a French think tank, Léger wrote a recent report arguing that all workers should be permitted naptime, an especially important respite for those working night shifts or anyone who routinely sleeps six or fewer hours daily. Such chronic sleep deprivation is associated with hypertension, diabetes, depression, obesity, cancer and even an increased risk of death. Research shows that short periods of sleep increase cognitive performance, reaction time and mood. In one study, subjects who took an afternoon nap were nearly twice as likely to solve a video-game problem as those who didn’t….