You’re in the middle of the afternoon, eyelids heavy, focus slipping. You close your eyes for half an hour and wake up feeling recharged. But later that night, you’re tossing and turning in bed, wondering why you can’t drift off. 1[■]
Napping has long been praised as a tool for boosting alertness, enhancing mood, strengthening memory, and improving productivity. Yet for some, they can sabotage nighttime sleep. Napping is a double-edged sword. Done right, it is a powerful way to recharge. Done wrong, it can leave you struggling to fall asleep later. 2[■]
Most people experience a natural dip in alertness in the early afternoon, typically between 1 pm and 4 pm. Our internal body clock creates cycles of wakefulness and tiredness throughout the day. The early afternoon lull is part of this cycle, which is why so many people feel drowsy at that time. Studies suggest that a short nap allows the brain to rest without slipping into deep sleep. But there’s a catch. 3[■] This is due to “sleep inertia”-the grogginess (昏沉) and disorientation that comes from waking up during deeper sleep stages. Once a nap extends beyond 30 minutes, the brain transitions into slow-wave sleep, making it much harder to wake up.
For certain groups, napping is essential. 4[■] A well-timed nap before a night duty can boost their alertness and reduce the risk of errors and accidents. Similarly, people who regularly struggle to get enough sleep at night-whether due to work, parenting, or other demands-may benefit from naps to bank extra hours of sleep that compensate for their sleep loss.
5[■] Age, lifestyle, and underlying sleep patterns all influence whether naps help or hinder. A good nap is all about strategy-knowing when, how, and if one should nap at all.