A short daytime nap can help a person maintain alertness and concentration and improve his emotional state. GERALDINE LING reports

You do not want to be caught sleeping on the job. On the other hand, you have yet to convince your boss of the benefits of power naps.

There is evidence that a quick nap in the day is beneficial to one’s health.

Day snoozes, also dubbed power naps and which last for about 10 to 20 minutes each, help to maintain alertness and concentration, said adjunct assistant professor Sridhar Venkateswaran, a consultant in respiratory medicine at Changi General Hospital.

Dr Chng Seo Yi, a paediatrician at SBCC Asthma Lung Sleep and Allergy Centre, who agrees, said daytime naps can have an invigorating effect and improve one’s emotional state.

However, there can be too little or too much of a good thing. Dr Sridhar said the benefits of power naps depend on their length.

Naps shorter than five minutes have no real benefit because they are too short and shut-eye beyond 30 minutes can cause sleep inertia.

Dr Chng explained that sleep inertia results in grogginess and decreased alertness – at least for about half an hour after rousing from a nap that has taken too long.

It makes sense, in such situations, to avoid tasks that require critical thinking or quick responses, like driving, until the effect wears off.

If you take a prolonged nap, she said, and your boss suddenly phones you to give you a task, it may be hard to fully grasp instructions as you are still groggy.

“It will be apparent to your boss that you have just woken up or been sleeping on the job,” she added.

To reduce sleep inertia, washing one’s face or doing stretching exercises for a few minutes can help, she suggested.

She said that research has found that the optimum time for a daytime nap is around 3pm, as people are naturally less alert then. This may be due to the body’s biological rhythm.

“This post-lunch sleepiness occurs whether lunch has been consumed or not,” she added.

Catching up on sleep
Dr Chng also noted that many people are sleeping less due to a hectic lifestyle. They then use the weekends and holidays to catch up on sleep and repay their sleep debt.

Dr Lim Li Ling, a consultant neurologist at the Singapore Neurology & Sleep Centre and president of the Singapore Sleep Society, said that adults need about six to eight hours of sleep daily.

Having less than four to five hours is considered too little for most people.

Dr Chng said that routinely sleeping too little increases one’s risk for obesity, heart disease and diabetes.

Prof Sridhar said sleeping in on weekends is generally okay. However, he warns that one can never fully repay the sleep debt incurred from sleeping too little on weekdays.