A siesta is good for your memory

There's nothing like a good nap after lunch, especially here in Spain. To fall into the arms of Morpheus, god of dreams, for thirty minutes mid-afternoon gives us a boost and improves learning and productivity. Businesses should not look unkindly on staff who take a nap, but rather should encourage them to do so. Thus concludes a study undertaken by the National University of Singapore (NUS), which once again shows that the Spanish custom of having a brief lie-down before starting any evening work should not be considered a symptom of laziness, but quite the opposite: one of intelligence.

The Singapore paper is not the first research study to sing the praises of the siesta. There have been previous studies, but this one is unique in that it has emphasised the impact that a quick nap after a meal can have on cognitive function. The brain needs to reset itself to continue to function at its best.

"Many know the benefits of napping, but the pressure to optimise time in the workday imposes restrictions that can make it impossible to take a regular nap," said specialist Ruth Leong, a researcher at the Centre for Sleep and Cognition, Yong Loo Lin School of Medicine in Singapore and report author.

Despite the many benefits that different investigations have attributed to it, the siesta is not for everyone. Neurologist Ana Fernández Arcos, coordinator of a study group on wakefulness and sleep disorders for the Spanish Society of Neurology (SEN), stated that they are not recommended for people who have trouble falling asleep at night.

In children, it depends on their age. Those under six years of age need a lot of rest, but those over that age should not have a siesta.

The recommendation for adults with no sleep problems is that they do not nap for more than 20 or 30 minutes. That time, "at most half an hour", is what, according to the University of Singapore, it takes to get brain activity back on track in the middle of the workday.

The study, published in the peer-reviewed journal Sleep, was carried out with a small sample of 32 young adults. Some were allowed to sleep for ten minutes, others for thirty, a third subgroup for a full hour and the fourth was allowed to nap freely until they woke up naturally.

The test subjects had their sleep controlled by the diagnostic test of polysomnography, an internationally recognised test used daily in hospitals that allows medics to verify quality of sleep and to check the existence of possible sleep disorders.

This measurement made it possible to determine "unequivocally" how long it took the volunteers to fall asleep and how long a nap should last. The researchers measured mood, subjective sleepiness (a sensitive indicator of insufficient sleep and impaired waking function), and cognitive performance at intervals of five minutes, thirty minutes, sixty minutes and up to 240 minutes after the volunteers had woken up.

The researchers observed that the participants took between ten and fifteen minutes to fall asleep. Naps lasting between ten minutes and one hour were clearly beneficial for positive mood, control of subjective feelings of sleepiness and alertness, all maintained well for up to four hours after waking up. The study allows us to conclude, according to its authors, that 10 minutes of sleep after eating is enough to reactivate the mind. However, only a nap of at least thirty minutes can yield specific benefits in memory encoding.

The improvements in alertness were moderate and no clear benefits in memory processing speed were found. The grogginess upon waking up and the sleepiness that ensued were only detected in those who slept between half an hour and one hour.

"A thirty-minute rest seems to have the best trade-off between having a reasonable siesta and reaping some benefit from it." The recommended time to sleep after eating is, therefore, half an hour, to which another ten minutes would have to be added for getting to sleep, making it 40 minutes in all required for that afternoon rest.

Sleep is considered a fundamental pillar for our well-being and health, as necessary as a good diet and regular physical exercise.

"Sleep is essential for health," stressed specialist Ana Fernández Arcos.

"We have more and more evidence that some sleep disorders could be closely linked to an increased risk of developing life-threatening conditions such as Alzheimer's or cardiovascular disease or are signs of poor control of epilepsy," she said.

Some 45% of the population will suffer from a serious sleep disorder for most of their lives. Scientific evidence suggests that twelve million people in Spain do not get a proper rest.