ONE in three people here is getting so little sleep that it is affecting his health, according to a recent editorial in the Annals, a journal by the Singapore Academy of Medicine.
People who do not sleep enough are more likely to become obese, and suffer from diabetes and heart problems, it said.
Insufficient sleep also increases the risk of transport and industrial accidents by 11/2 to two times, according to Professor Michael Chee of the centre for cognitive neuroscience at the Duke-NUS Graduate Medical School.
Prof Chee, who wrote the editorial, cited figures from various studies that were done both locally and internationally over the past decade.
A yet-to-be-published study conducted here found that people who sleep five hours or less have higher levels of coronary artery calcium, which increases the risk of heart attacks.
Prof Chee said: "It is known elsewhere, but when you see it in your own people, it makes you think twice."
Adults should get seven to 7 1/2 hours of sleep. At the very least, it should be six hours, although this would still affect the performance of the majority, said Prof Chee, a neurologist who has been studying how a lack of sleep affects the brain.
Children need more sleep as their brains and bodies are still developing.
Working, socialising and commuting are the main reasons Singaporeans stay awake past bedtime, he noted in his report, which was funded by the National Medical Research Council Singapore.
But sacrificing sleep may have serious consequences. It "is associated with increased all-cause mortality", Prof Chee warned.
Lack of sleep causes people to crave either very sweet or salty-greasy food, which are bad for health and leads to obesity, he said. Also worrying, he noted, is that after a few days of not getting enough sleep, many think they have adjusted and are fine.
But research has shown that they are more prone to making mistakes than they are aware of.
The young, in particular, tend to sleep less than they should.
A study of 2,000 students at the National University of Singapore and the Nanyang Technological University found that they sleep an average of 6.2 hours.
Prof Chee said: "This is short. They should be thinking, developing memories and consolidating them, and this is going to affect them."
Another study of 60 teenagers here, which used motion sensors while they slept, found that they averaged only 4.36 hours due to fragmented sleep which sees them waking several times a night. "This is scary," he said.
A study by University College London of 17,465 students from 27 universities in 24 countries found that Asians in general average less than seven hours of sleep a night, compared with more than eight for students in Europe.
Explaining why this might be so, Prof Chee said: "Despite shifting mores, traditional values of hard work continue to inure Asians to long hours and short sleep."
Associate Professor Stacey Tay, who heads paediatric neurology at the National University Hospital (NUH), and has researched sleep in pre-school children here, said toddlers "were indeed getting less night-time sleep".
They sleep 8.5 hours at night and have another 1.6-hour nap in the day.
"Both total sleep and night- time sleep were shorter than the recommended sleep duration of 11 to 13 hours a night for the pre-school age, and significantly less compared to values from Western studies," she said.
"Shortage of sleep may result in migraine and tension-type headaches, attention difficulties, and affect memory and academic performance."
The ill-effects of insufficient sleep on the population, cautioned Prof Chee, could be as big a health scourge as smoking and consuming sweetened soft drinks.
His colleague, Dr Joshua Gooley, a chronobiologist who studies sleep patterns, said: "Short sleep is also associated with increased risk for psychiatric conditions and can negatively impact mood and relationships."
Both he and Prof Chee feel that the early school start times affect students.
Said Dr Gooley: "Many teenagers struggle with waking up early because their body clock is telling them that they should still be sleeping."
Added Prof Chee: "There is abundant data to suggest that it's better to start school later."