Sleep is essential to our existence but tell that to the multitudes of people in Hong Kong and elsewhere who are in chronic need of more sleep. You may think you can catch up later, but think again, warns Dr Esther Lau of Psychology who has conducted a number of studies on sleep.

“When I was younger, I thought this way, too,” she said. “I could stay up all night and study hard and play hard and I thought sleep was not important.

“But a growing body of research evidence is pointing to the fact that sleep does affect your functioning to a large extent and accumulating sleep debts predicts how well you function during the day.”

For one thing, poor sleep over the long run can affect your higher thinking skills, which involve complex executive functioning that enables you to keep track of many different things at the same time and access the information you need to do that. Dr Lau and her colleagues found both adults and children with sleep apnoea, a chronic condition that causes interrupted breathing during sleep, had impaired executive functioning even after impairments in lower-level functioning were reversed.

Sleep-mood connection

They are also showing, in another study, that poor sleep can affect your mental health over the long run. This research involves an on- going longitudinal study with several thousand people, mostly university students, that is looking at the pathway between sleep and mood, and the mediating role of thinking styles (pessimist or optimist). As Dr Lau put it: “Is your mood so bad that your sleep is affected, or is it the other way around?” The preliminary results suggest a greater role for sleep.

“We are seeing that poor sleep is not just a symptom of poor mental health. It predicts your mental health. In the past sleep was often considered a symptom, so if you had depression and you had insomnia, the depression caused your insomnia. But in recent years there are more and more studies showing sleep actually predicts your mental health, even in people who do not have any depression or other problems. So if you aren’t sleeping well on a constant basis, it has a large impact on your well-being a few years later,” she said.

Dr Lau is also interested in researching normal sleep, not only disorders. Here, she sees opportunities for using sleep towards positive ends. A study on ‘chronotypes’ – whether you are a morning or evening person – produced unusual findings by focussing on students in university halls in Hong Kong. While other studies show morning people perform better on most measures, the opposite happened in the halls. Night owls adjusted better and were less likely to quit hall a year later, a finding which could help students make decisions about living in a hall and inform administrators on hall policies and education.

Take a nap

Napping is another normal sleeping activity of interest and it is showing potential for a therapeutic role. Dr Lau has shown it has a positive impact on higher cognitive functioning, echoing her findings on sleep apnoea and adding to other studies that found it improved attention, vigilance and mood. In future she hopes to explore links between napping and emotional processing. “If we find napping has a positive effect on emotional processing, it could be beneficial for clinical populations such as people with traumatic memories or post-traumatic stress disorder who are dealing with a lot of negative emotions,” she said.

Dr Lau directs a sleep laboratory dedicated purely to research and she works with a wide range of collaborators in different branches of Medicine and Social Sciences.

“I try to throw sleep questions into whatever study I’m doing,” she said. “Sleep is important, that’s the bottom line. And it plays a major role in one’s well-being. So if people are having trouble sleeping, we shouldn’t look at it as something that will go away and think that as long as the person is not diagnosed with depression or an anxiety disorder it doesn’t warrant clinical attention. I think that is just wrong thinking.

“My hope is that our research programme can reveal the different roles of sleep in our lives in predicting mental health, cognitive performance, academic functioning, even social functioning.

“My dream would be if the University could provide sleep pods so people could pop in and sleep for 30 minutes. That would boost the performance of both students and staff, and the mood and mental health of the University community,” said Dr Lau.■

Dr Lau giving a public lecture based on research findings from the HKU Sleep Laboratory and other sleep studies.