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Good sleep contributes to health and performance. However, insufficient and poor sleep are very common among adolescents today. This study examines cross-national differences in adolescents' sleep and activity patterns across Finland, France, Hungary, Italy, Netherlands, South Africa, South Korea, Spain, and the UK, using an innovative 24-hour time-use approach with time-diary data (N = 25,248 diaries; mean age 15.4 years; 50.3% girls). Sleep duration ranges from 7:21 hours (South Korea) to 8:46 hours (South Africa, UK) on schooldays and from 9:13 hours (South Korea) to 10:33 hours (Netherlands) on non-schooldays. South Africa shows the earliest and Spain the latest sleep onsets and wake-up-times. Insufficient sleep duration (i.e. less than 8 hours) ranges from 19% (South Africa) to 69% (South Korea) on schooldays. Activity patterns before sleep (e.g. eating, screen time, studying) also differ strongly across countries. Our findings could support policy makers in developing effective strategies to improve adolescent sleep. [ABSTRACT FROM AUTHOR]

Background: The ways children spend their time is one of the most valuable inputs for healthy child development. It is unknown which time investment yields the greatest return for children's language and behavioural outcomes at school entry.Methods: We used data from the first three waves (2004, 2006, 2008) of the Longitudinal Study of Australian Children (n = 4253). At every wave, parents completed 24-h time-use diaries on one randomly selected week and one weekend day. The amount of time children spent on 11 activities at ages 0-1, 2-3 and 4-5 years was analysed. Receptive vocabulary was assessed using the Peabody Picture Vocabulary Test, and externalizing behaviours were measured by the Strengths and Difficulties Questionnaire, completed by parents and teachers at 4-5 years. To identify which time investment in the first 5 years of life mattered most for children's outcomes, a new production function was developed. This production function was estimated using a log-log linear regression model.Results: Relative to other time investments, time spent on educational activities at 2-3 years of age was the most important time investment for receptive vocabulary and behavioural outcomes at school entry. After adjusting for confounding, every 1 h invested in educational activities at 2-3 years was associated with a 0.95% [95% CI (confidence interval): 0.62, 1.28] increase in receptive vocabulary, and a -5.72% (95% CI: -7.71, -3.73) and -9.23% (95% CI: -12.26, -6.20) reduction in parent- and teacher-reported externalizing problem behaviours. Time invested in play was also important to both receptive vocabulary and behaviour. One hour invested in play at 2-3 and 4-5 years was associated with a 0.68% (95% CI: 0.38, 0.98) and 0.71% (95% CI: 0.39, 1.03) increase in children's receptive vocabulary at school entry. In addition, time invested in play at 2-3 and 4-5 years was associated with reduced problem behaviours at school entry. In contrast, screen time at all ages was associated with poorer parent- and teacher-reported externalizing problem behaviours.Conclusions: These results suggest that time invested in educational activities at 2-3 years of age yield the greatest return for children's receptive vocabulary and behaviour at school entry. [ABSTRACT FROM AUTHOR]

Researchers analysing time-use data often estimate limited dependent variable models because time spent must be nonnegative and cannot be more than the total amount of time in a given observation period. While the traditional empirical technique applied to such cases is maximum likelihood estimation of a Tobit (censored regression) model, recent debate has questioned whether linear models estimated via Ordinary Least Squares (OLS) are preferable. On the one hand, Tobit models are deemed necessary to address the significant censoring (i.e. large numbers of zeroes) typically found in time-use data, in the face of which OLS estimators would be biased and inconsistent. Yet, optimization occurs over a longer period than that covered by the typical time diary (often a day), and thus some argue that reported zeroes represent a measurement problem rather than true nonparticipation in the activity, in which case OLS would be preferred. We provide direct empirical evidence on this question using the Australian Time Use Surveys, which record time-use information for two consecutive diary days, by estimating censored and linear versions of a parental child care model for both 24-hour and 48-hour windows of observation in order to determine the empirical consequences of estimation technique and diary length. [ABSTRACT FROM PUBLISHER]