On Monday, World Sleep Day, sleep specialists said the lack of quality sleep has become a public health issue because of the rising number of people who are not getting adequate sleep.

Dr. Michael Sarte, president of the Philippine Society of Sleep Medicine, said Filipinos may not be realizing the effect of quality sleep on people's overall physical and mental health.

"Most people do not know that a lot of illnesses can be traced to the fact that they do not get enough sleep," he said.

"The more they can be informed, the better they can be armed," he said.

He said quality sleep for adults should have four to five cycles of both deep sleep and light sleep, five to seven hours a night.

Light sleep is when a person drifts in and out of sleep and can be easily awakened. In this stage, the eyes move slowly and muscle activity slows down.

Deep sleep is when a person falls deep in slumber. There is no eye movement or muscle activity, and the brain produces delta waves almost exclusively.

On the other hand, children require at least nine to ten hours of quality sleep, he said.