Sleep problems are common in adolescents. Studies have consistently demonstrated that sleep disturbances are prevalent, affecting up to 50% of this population. In this project, the investigators aim to map out sleep patterns, risk factors, and obstacles for sleep in adolescents, capturing the diversity of societal factors that shape the sleeping habits of adolescents. The investigators aim to recruit school-aged adolescents (aged 12-18 years old) in 12 countries across 15 research centres (N = 1000 per centre) to fill in the questionnaire covering sleep-wake patterns, sleep problems, mood, behavioral, daytime functioning and their attitude and perception towards sleep.

Introduction Sleep problems are common in children and adolescents. In particular, extensive evidence consistently demonstrated that sleep disturbance is prevalent affecting up to 30% of this population. The situation is worrying as expanding body of evidence has demonstrated the close relationship between inadequate sleep and daytime impairment, obesity, diabetes, cardiovascular complications, disruptive behaviors, mental health and poor academic performance.

There is a web of interactive factors that contribute to sleep disturbance including biological, social, and cultural factors. For example, during adolescence, teenagers experience a circadian delay in their sleep, leading to a delayed bedtime and this sleep pattern is further exacerbated by increasing technology usage. In addition, cultural influences also play a significant role in their sleep. Mindell and colleagues compared sleep patterns between Asian and Caucasian young children and found that Asian children had significantly later bedtimes and shorter total sleep time as well as different parental perceptions towards their children's sleep problems. A similar trend was also evident among adolescents with Asian teens consistently having later bedtimes, earlier wakeup times and shorter sleep than their Caucasian counterparts. The difference in sleep patterns and sleep habits not only existed between Asian and western countries, but discrepancies were also observed within the Asian countries. A previous study that compared sleep duration between children in Hong Kong and Shanghai revealed that Hong Kong children have later bedtimes and wakeup times as well as shorter sleep than Shanghai children, particularly during weekdays.

Although there is evidence supporting the cultural influence on adolescent sleep-wake patterns, most of the studies are country specific which do not allow adequate cross-cultural comparison. Importantly, substantial cultural, religious, and economic differences exist within and between countries in Asia. A more comprehensive coverage of different countries in Asia will allow for a better understanding of specific sleep patterns in relation to the rich cultural variety across the Asian region.

Moreover, previous studies utilized different inventories, various age groups, and different measurement methods. The variations in methodology make it difficult to make an accurate comparison between different cultures. Identifying the similarities and differences in sleep patterns/problems as well as associated factors across various regions, will allow us to have a more thorough understanding of their sleep, which is an important step in devising countermeasures for mitigating this concerning situation.

In view of the above-mentioned limitations of previous studies and the necessity of multicenter collaboration (15 research centres across 12 countries), the aim of the current study (ACROSS study) is to gather sleep researchers from various Asian countries in order to:

1. To conduct a sleep survey in Asian adolescents
2. To explore the Cultural differences in sleep patterns and problems
3. To evaluate the Risk factors associated with sleep problems
4. To understand the Obstacles to obtain adequate sleep
5. To promote health Sleep in Schools

Methods Participants Participants will be recruited through schools, public advertisement, poster and emails in Asian countries. Adolescents aged 12-18 years old will be invited to complete the questionnaire either in online form or in paper form. The administration of the questionnaire will be conducted during school-term avoiding the exam period.

Participants will be invited to fill in the questionnaire covering the following aspects:

1. Demographics: gender, age, height, weight, education ethnicity, and religion etc. Parental education, employment status and socioeconomic class will be assessed.
2. Sleep patterns and problems: sleep wake patterns, napping habits, various sleep symptoms, chronotype will be covered
3. Mental wellbeing: Mood symptoms will be assessed using Patient Health Questionnarie-2; Anxiety measured by General Anxiety Disorder-2, Stress by Perceived Stress Scale-4, and also overall health status
4. Lifestyle factors: Time spent on different activities such as electronic media use, physical activities, homework, entertainment etc. will be collected
5. Attitude and perception towards sleep: Adolescent's perception towards different sleep conditions will be assessed. Parent and school practice related to sleep measure/issues will also be assessed.

Inclusion Criteria:

• School-going adolescents aged 12-18 years old

Exclusion Criteria:

• Nil.

School-going adolescents aged 12-18 years old will be invited to participate.