Q (Nov 28) I am a Secondary Four student who recently had some sleep problems. Though I go to bed by 11pm and wake up at 6.30am, I feel tired all day. And I always fall asleep during lessons.

I also dream a lot and often have mysterious dreams. Is this due to exam stress? Or is it due to lack of exercise? Shall I go and see a doctor?

A From the information given, it appears likely that you have excessive daytime sleepiness related to chronic sleep deprivation.

The average sleep requirement for a 16-year-old is about nine hours. It is not surprising that with 61/2 to 71/2 hours a day over weeks to months, you experience tiredness and excessive daytime sleepiness.

Stress may also aggravate the situation.

Dreams that are 'mysterious', 'weird' or 'confusing' are common in teenagers your age and is a normal phenomenon.

Despite the rapid advances in the understanding of sleep physiology, there is yet no consensus regarding the meaning of dreams. What we do know is that adequate dream sleep is needed for information processing, learning and memory.

Lack of exercise does not directly contribute to poor sleep or dreams although regular exercise at least four hours or more from bedtime may help you to sleep better.

I would recommend a total sleep time of at least 8 1/2 to 9 1/2 hours a day, and adequate time for rest and recreation in the midst of examination stress.

If your symptoms persist or progress, you may benefit from a visit to your family doctor who could decide if onward referral for further evaluation - to exclude co-existing sleep and other disorders - is necessary.

DR JENNY TANG, DIRECTOR, SLEEP DISORDERS PROGRAM, DEPARTMENT OFPAEDIATRICS, KKWOMEN'S AND CHILDREN'S HOSPITAL