Sleep duration or bedtime? Exploring the relationship between sleep habits and weight status and activity patterns

Area of Science:

• Pediatrics
• Sleep Science
• Public Health

Background:

• Sleep timing is a crucial factor influencing child development and health.
• Understanding the impact of specific sleep schedules on activity and weight is vital for public health initiatives.
• Previous research has highlighted associations between sleep duration and health outcomes, but the role of sleep timing requires further investigation.

Purpose of the Study:

• To investigate the effects of early versus late bedtimes and wake times on time use and weight status in Australian school-aged children.
• To analyze the relationship between different sleep-wake patterns and physical activity, screen time, and body mass index (BMI).

Main Methods:

• An observational, cross-sectional study was conducted.
• Data were collected from 2200 Australian adolescents aged 9–16 years using time-use interviews and pedometers.
• Participants were categorized into four sleep-wake groups: Early-bed/Early-rise, Early-bed/Late-rise, Late-bed/Early-rise, and Late-bed/Late-rise.

Main Results:

• Adolescents with late bedtimes and late wake times (Late-bed/Late-rise) exhibited significantly more daily screen time (48 min/d) and less moderate-to-vigorous physical activity (MVPA) (27 min/d) compared to those with early sleep schedules.
• The Late-bed/Late-rise group had a higher mean BMI z-score (0.66 vs. 0.45) and were more likely to be overweight or obese (1.47 times), obese (2.16 times), have low MVPA (1.77 times), and high screen time (2.92 times).
• Late sleep schedules were also associated with socioeconomic factors, with Late-bed/Late-rise adolescents more likely to come from poorer households, live in major cities, and have fewer siblings.

Conclusions:

• Late bedtimes and late wake times are independently associated with an unfavorable profile of physical activity and weight status in Australian adolescents.
• These findings suggest that optimizing sleep timing, irrespective of total sleep duration, may be a key strategy for improving child health.
• Public health interventions should consider sleep timing as a modifiable factor to address childhood obesity and promote healthy lifestyles.