SINGAPORE - On Friday (March 16), people across the globe will wake up to World Sleep Day, an annual celebration of sleep and a call to action on issues related to a good night's rest.

Here's a look at some facts and data about napping:

1. Singaporeans sleep the least

Singaporeans sleep just slightly more than seven hours day, the least number of hours among places surveyed, says a 2016 study on sleep schedules.

The Republic came in ahead of Japan (7.5 hours) and Brazil (7.6 hours) in the study published by the American Association for the Advancement of Science.

Singaporeans were also among those with the latest bedtime of 11.45pm, even as most of them woke up at about 7.10am.

Among the most well-rested countries were Belgium, the Netherlands and New Zealand.

Citizens in these countries slept for at least eight hours every day.

Singapore's results echo a similar study by SingHealth Polyclinics last year, which found that four in 10 people, or 44 per cent, lack sleep on weekdays.

2. More Zzzs for Gen Z

Sleep patterns differ across generations. If you belong to Generation Z, chances are you go to bed only after midnight but lie in a little bit longer in the morning. And as a result, you probably sleep the most.

Data scientists for health tracking device Fitbit have found inter-generational differences when it comes to sleep.

According to its latest figures, Generation Z, defined as those between the ages of 13 and 22, go to bed at 12.08am and wake up at 8.12am. This gives them at least eight hours of rest.

In contrast, baby boomers aged 52 to 71 sleep the least, averaging just six hours and 33 minutes a night.

While rapid eye movement, or REM, and light sleep remain stable throughout a person's lifetime, he will get less deep sleep as the years pass, Fitbit's data shows.

At age 20, a person spends about 17 per cent of their rest in the deep sleep stage, but this drops to 13 per cent at 70 years old.

Pain, illness and medical problems, which affect the elderly more frequently and may interfere with sleep, are possible explanations.

3. What keeps us awake?

About six in 10 adults worldwide face problems getting the sleep they need, with about 26 per cent plagued by insomnia.

Another 21 per cent fail to get a good night's sleep because of snoring.

This is according to recent findings from the Royal Philips' annual global survey, which was released this week in conjunction with World Sleep Day.

And if you find yourself up at night fretting about work, you are not alone.

Nearly six in 10 adults suffer from disrupted sleep in the past three months due to worrying. In particular, 34 per cent of them were worried about financial or economic issues.

4. If not slumberland, then what?

While most people recognise the importance of catching forty winks, many of them tend to place greater emphasis on getting a good workout or eating right, when it comes to improving their health.

Several other daily activities rank higher in priority too, according to last year's sleep report by Royal Phillips.

Adults in the United States, France and Germany admit that spending time with their family is more important than sleep.

In Netherlands, most people stay up to watch their favourite television shows or movies.

And in Japan, many sacrifice snooze time to surf the Internet.

Nearly a quarter of adults also believe that sending late night work emails, when everyone is sleeping, shows that they care more about their job.

5. Bedroom comforts and habits: A nice scent, tea and no clothes please

What makes a great bedroom? The first international bedroom poll by the United States' National Sleep Foundation found that about nine in 10 Mexicans and Germans feel more relaxed if their bedroom has a fresh, pleasant scent.

But a majority of respondents in the six countries surveyed also said that they take steps to ensure their bedrooms smell the way they want.

The poll also shed light on a few interesting cultural differences in bedtime rituals and habits.

It found that about two-thirds of Mexicans and nearly half of Americans meditate or pray before they head to bed.

In Britain, two in five drink a soothing beverage, such as tea, before about one-third of them in the country sleep naked.