Almost 40 percent of Chinese adults suffer from insomnia, the China Sleep Research Society says, in a report released ahead of World Sleep Day, which falls on March 21.

The sleep time of Chinese adults has dropped at a rate of 0.71 minutes per year since 1900, which means that the current average sleep time for an adult is 1.5 hours less than it was in 1900. The China Sleep Research Society also reports that 40 percent of Chinese adults had taken a nap during the day within the last month.

There are many sleep quality monitoring gadgets on the market which may help people keep track of their sleep, but an even more effective way is to keep a sleep journal. The sleep efficiency ratio, or total sleep-time to time lying in bed over several consecutive days, is an indicator of an individual's sleep quality. A ratio lower than 85 percent is a bad sign, the report says.

Insomnia sufferers may be three to four times more likely to develop depression than those who sleep well, but only 21 percent of Chinese adults with sleep problems seek medical assistance, the newspaper reports.

Counting sheep and drinking wine will not help you nod off, say the experts, but a foot spa, a small cup of milk, or a philosophical book can do the job.

Having a long lie at the weekend can help those who don't get enough sleep during the working week, and can even reduce the risk of obesity to a certain degree, but this practice should not be adopted as a long-term replacement for sound sleep through the week.