The inter-relationship between physical activity, sedentary behaviour and sleep (collectively defined as physical behaviours) is of interest to researchers from different fields. Each of these physical behaviours has been investigated in epidemiological studies, yet their codependency and interactions need to be further explored and accounted for in data analysis. Modern accelerometers capture continuous movement through the day, which presents the challenge of how to best use the richness of these data. In recent years, analytical approaches first applied in other scientific fields have been applied to physical behaviour epidemiology (eg, isotemporal substitution models, compositional data analysis, multivariate pattern analysis, functional data analysis and machine learning). A comprehensive description, discussion, and consensus on the strengths and limitations of these analytical approaches will help researchers decide which approach to use in different situations. In this context, a scientific workshop and meeting were held in Granada to discuss: (1) analytical approaches currently used in the scientific literature on physical behaviour, highlighting strengths and limitations, providing practical recommendations on their use and including a decision tree for assisting researchers’ decision-making; and (2) current gaps and future research directions around the analysis and use of accelerometer data. Advances in analytical approaches to accelerometer-determined physical behaviours in epidemiological studies are expected to influence the interpretation of current and future evidence, and ultimately impact on future physical behaviour guidelines.

The 24-h day—containing physical activity, sedentary behaviour and sleep—in pre-school children has not yet been extensively investigated. The aim of the current study was to investigate pre-schoolers’ compliance with the 24-h movement behaviour guidelines (i.e., three hours/day total physical activity, a maximum of one hour/day of screen time and 10–13 h sleep/night). In total, 595 pre-schoolers (53.3% boys, mean age: 4.2 years) provided complete data for the three behaviours. Physical activity was objectively measured with accelerometers, while screen time and sleep were parent-reported through questionnaires. The proportion of pre-schoolers complying with the 24-h movement behaviour guidelines was calculated on weekdays and on weekend days. Low compliance rates were found: 10.1% on weekdays and only 4.3% on weekend days. The majority of pre-schoolers complied with the sleep duration guidelines (>90% on weekdays and weekend days), followed by the screen time guidelines (61% on weekdays and 28% on weekend days). The lowest compliance rates were found for physical activity (<20% on weekdays and weekend days). Overall, low percentages of pre-schoolers complying with the 24-h movement behaviour guidelines were found, and the lowest compliance was found for physical activity.

ObjectiveTo examine the joint associations of daily time spent in different intensities of physical activity, sedentary behaviour and sleep with all-cause mortality.MethodsFederated pooled analysis of six prospective cohorts with device-measured time spent in different intensities of physical activity, sedentary behaviour and sleep following a standardised compositional Cox regression analysis.Participants130 239 people from general population samples of adults (average age 54 years) from the UK, USA and Sweden.Main outcomeAll-cause mortality (follow-up 4.3–14.5 years).ResultsStudies using wrist and hip accelerometer provided statistically different results (I2=92.2%, Q-test p<0.001). There was no association between duration of sleep and all-cause mortality, HR=0.96 (95% CI 0.67 to 1.12). The proportion of time spent in moderate to vigorous physical activity was significantly associated with lower risk of all-cause mortality (HR=0.63 (95% CI 0.55 to 0.71) wrist; HR=0.93 (95% CI 0.87 to 0.98) hip). A significant association for the ratio of time spent in light physical activity and sedentary time was only found in hip accelerometer-based studies (HR=0.5, 95% CI 0.42 to 0.62). In studies based on hip accelerometer, the association between moderate to vigorous physical activity and mortality was modified by the balance of time spent in light physical activity and sedentary time.ConclusionThis federated analysis shows a joint dose–response association between the daily balance of time spent in physical activity of different intensities and sedentary behaviour with all-cause mortality, while sleep duration does not appear to be significant. The strongest association is with time spent in moderate to vigorous physical activity, but it is modified by the balance of time spent in light physical activity relative to sedentary behaviour.