Can a Nap Make Up for a Bad Night's Sleep?

For many, napping remains the best ally after nights that are short, fragmented, or completely sleepless. But is it really an effective and healthy reflex? Insights from a neuroscientist.

More than a third of French people are dissatisfied with the quality of their sleep, as reported in March by a survey from the National Institute of Sleep and Vigilance and MGEN. The causes of poor sleep are varied (stress, screen exposure, nightmares, noise pollution), but there are ways to counteract the effects of a less restorative night on the body. Among these is the famous nap, which, according to its enthusiasts, helps recharge batteries and catch up on the fatigue accumulated during the previous shortened night. Really?

A Minimum Amount of Time for Physical and Mental Recovery

In reality, as explained by Armelle Rancillac, a neuroscience researcher at Inserm and sleep specialist, napping is a physiological and individual need whose benefits depend primarily on its duration. For example, the short format of the power nap, also known as a "flash" nap and popularized by artist Salvador Dalí, only lasts a few seconds or minutes. You hold an object in your hand until it falls with a crash as you fall asleep and wake you up. The goal here is not to recover the body but rather to energize in order to stimulate creativity, the neuroscientist specifies.

If, after a bad night, one wishes to fight drowsiness and regain energy, the napping time should be extended to at least 20 minutes. "Sleeping enough in the middle of the day helps to reduce the sleep pressure that has accumulated with the bad night," confirms the neuroscience researcher. During this time, a bit of slow-wave sleep is produced, the phase supposed to help the body recover better. "Thanks to this type of nap, we can restore alertness, concentration, and cognitive performance," summarizes Armelle Rancillac.

In case of significant sleep deficit, for example after a sleepless night or after insomnia that has halved our sleep quota, the neuroscientist advises (when possible) to sleep for a full cycle, between 90 and 120 minutes, to mimic a "mini-night." In practice, "during a nap of an hour to an hour and a half, our body will produce more slow-wave sleep, which will regenerate tissues and secrete necessary hormones for the body, like growth hormone," she explains. Another important sleep stage will also be stimulated, the so-called "REM" stage, where the brain consolidates learning and regulates emotions.

A Habit to Monitor and Adapt

Regardless of the nap's duration, the golden rule is not to nap too late in the day, as this can have detrimental effects on the following night. "The ideal is not to nap after 5 pm to allow adenosine, the hormone responsible for sleep onset, enough time to recharge before being released in the evening," indicates Armelle Rancillac. To ensure the effectiveness of the daytime nap, one must also assess their energy level after waking up. If one still feels tired, it may be a sign that the sleep debt is not sufficiently repaid, suggests the neuroscientist, or that one suffers from a real sleep disorder. In this case, it is advisable to consult a health professional. Moreover, many studies highlight sleep deprivation as a risk factor for cardiovascular diseases, type II diabetes, hypertension, overweight, and to a lesser extent, depression or anxiety.

Other reflexes are just as important as napping to protect one's sleep. Starting with regular waking and sleeping times, even on weekends, the neuroscientist reminds. During the day, it's also essential to activate the synchronizers of the sleep-wake rhythm by exposing oneself as much as possible to natural light. A well-informed sleeper is worth two.