A study published in Science Advances has found that women sleep more than men. The study also revealed that people from Netherlands get more sleep than people from Japan and Singapore. The data was gathered using the Entrain app, which was developed by a team of researchers at the University of Michigan to help people overcome jetlag. Users had the option to share their sleeping pattern data with the team so they could better assess the overall global sleep situation.

Entrain simulates the user’s circadian clock on the phone and makes mathematically optimal lighting recommendations to help them adjust as fast as possible to new time zones and schedules.

The scientists asked an estimate of 6,000 people over the age of 15 to anonymously send data about their sleep and wake up times and their lighting environments. The app also asked users to send data about their gender, country, time zone and ages.

The study found that people in Singapore and Japan on average slept for 7 hours and 24 minutes. People from the UK slept for just under 8 hours, which was just a few hairs short of the time slept by the French. Dutch people, on the under hand, received the most sleep, about 8 hours and 12 minutes.

The study also showed that women slept on average 30 minutes more than men every night, especially those within the age groups of 30 to 60. It also showed that people who spent more time in natural sunlight tend to go to sleep earlier. So people who work outside such as construction workers tend to sleep at an earlier hour. Age also affected sleep durations, especially in men. Young men had a wide range of sleep patterns and their sleep and wake up times had a greater variation. In older men the sleep duration greatly narrowed, according to one of the researchers Professor Daniel Foger. Older men were getting less than the recommended 7 to 8 hours sleep every night.

Although a difference of about 30 to 48 minutes in sleep might not seem much but as time goes on, the sleep deprivation can get compounded which can be quite dangerous. According to the study, people who lack proper sleep suffer a reduction in their cognitive abilities without them knowing. “Impaired sleep presents an immediate and pressing threat to human health,” the study said.

The average time slept in the bed had the biggest impact on the time spent in bed. At what time the country woke up in the morning had little effect on the sleep duration, rather at what time the group went to sleep in the night.

Prof Foger said that there is a constant contradiction between people’s desire to stay up late and motivation to wake up early. He said that there is a “global sleep crisis” going on and society is to blame for it. He elaborated that society is forcing us to stay up late but wake up early so our sleep is being sacrificed in the process. He said, “If you look at countries that are really getting less sleep, I’d spend less time worrying about alarm clocks and more about what people are doing at night — are they having big dinners at 22:00 or expected to go back to the office?”

In most cases office workers had sleep problems, known as shift work sleep disorder which can lead to very serious health problems.

Sleeping Pattern: How Sleep Works?

Sleep is regulated by body’s internal clock known as the circadian rhythm. Circadian rhythm is affected by external stimuli known as zeitgebers, which means time givers in German, the most important being external light. The brain’s circadian clock is located in the hypothalamus which is responsible for regulating hormones in the body. The hypothalamus uses zeitgebergs to synchronize the circadian clock with the earth’s 24 hour rotation cycle.

The brain’s circadian clock is responsible for regulating sleeping and feeding patterns, body temperature, alertness, body restoration processes such as cell regeneration, and hormone production. Most important hormones regulated by the clock are melatonin and cortisol.

Melatonin affects the sleep cycles as it is released by the body when there is darkness. So at night time the body automatically starts feeling drowsy because of melatonin. Cortisol affects sleep in a multiple ways. It is a stress hormone that is released in stressful situations. When cortisol release becomes chronic, our sleep gets affected. So increased stress levels lead to elevated cortisol levels, which can lead to sleep disorders.

Normal sleep cycle is made of light sleep, deeper slow-wave of sleep and REM sleep. Light sleep includes stages 1 and stages 2 in the sleep cycle. Stage 1 sleep is considered the transition stage between sleep and wakefulness. This period lasts for 5 to 10 minutes and is made up of very slow brain waves, known as theta waves. Stage 2 lasts for about 20 minutes and involves mixed frequency brain waves with rapid brain activity bursts known as sleep spindles. During this stage body temperature starts to decrease and heart rate begins to slow.

Deeper sleep occurs in stages 3 and 4. Stage 3 sleep is identified by 20-50% slower brain waves, known as delta waves. It is the transition stage between light to very deep sleep. Stage 4 has more than 50% of slower brain waves. This stage lasts for about 30 minutes. Stage 5 is known as REM sleep and in this stage most of the dreams occur while respiration rate and brain activity increase. The ideal sleep cycle begins in stage 1 and progresses to stages 2, 3, and 4. After stage 4, stages 3 and then 2 are repeated before stage 5, the REM phase, begins. The body usually returns to stage 2 after REM sleep is over. First cycle of REM sleep lasts for about 90 minutes, with each cycle the duration of REM sleep increases.