Health outcomes associated with reallocations of time between sleep, sedentary behaviour, and physical activity: a systematic scoping review of isotemporal substitution studies

Abstract

BackgroundDuring a 24-h day, each given period is spent in either sedentary behaviour, sleeping, light physical activity (LPA), or moderate-to-vigorous physical activity (MVPA). In epidemiological research most studies have traditionally analysed the associations of these behaviours in isolation from each other; that is, without taking into account the displacement of time spent in the remaining behaviours. In recent years, there has been a growing interest in exploring how all the behaviours across the energy expenditure spectrum influence health outcomes. A statistical model used to investigate these associations is termed an isotemporal substitution model (ISM). Considering the increasing number of ISM-based studies conducted in all age groups, the present paper aimed to: (i) review and summarise findings from studies that employed ISM in sleep, sedentary behaviour, and physical activity research; (ii) appraise the methodological quality of the studies; and (iii) suggest future research directions in this area.MethodsA systematic search of ten databases was performed. The Newcastle–Ottawa scale was used to assess the methodological quality of the included studies.ResultsFifty-six studies met the inclusion criteria, all being of moderate or high methodological quality. Associations were reported for exchanged time varying from one minute to 120 min/day across the studies, with 30 min/day being the most common amount of time reallocated. In total, three different ISM methodologies were used. The most commonly studied health outcomes in relation to isotemporal substitutions were mortality, general health, mental health, adiposity, fitness, and cardiometabolic biomarkers. It seems that reallocations of sedentary time to LPA or MVPA are associated with significant reduction in mortality risk. Current evidence appears to consistently suggest that reductions in mortality risk are greater when time spent sedentary is replaced with higher intensities of physical activity. For adiposity, it seems that reallocating sedentary time to physical activity may be associated with reduced body mass index, body fat percentage, and waist circumference in all age groups, with the magnitude of associations being greater for higher intensities of physical activity. While there is a relatively large body of evidence reporting beneficial associations between the reallocation of time from sedentary behaviour to LPA or MVPA and cardiometabolic biomarkers among adults, there is a lack of studies among children, adolescents, and older adults. Although some studies investigated general health, mental health, and fitness outcomes, further investigation of these topics is warranted. In general, it seems that the strongest association with health outcomes is observed when time is reallocated from sedentary behaviour to MVPA. Most studies did not account for sleep time, which is a major limitation of the current evidence.ConclusionsThe current evidence indicates that time reallocation between sleep, sedentary behaviour, LPA, and MVPA may be ass...

Association between Reallocation Behaviors and Subjective Health and Stress in South Korean Adults: An Isotemporal Substitution Model

“…In contrast, increasing MVPA at the expense of SB was favorably associated with health-related quality of life in Australian mid-age adults, but increasing LPA at the expense of SB resulted in a negative association [17]. Reallocating effects could vary depending on outcome variables or population type [16], due to the discrepancy of PA participation across age groups [28]. Our results here provide the first evidence of age-related variation in reallocation effects and subjective health.…”

“…The isotemporal substitution (IS) model has emerged as a new method to determine the effects of changing time allocation across activities on a given outcome variable [14], while adjusting for covariates [15]. Data from the IS model helps health professionals develop PA-promoting strategies within a finite and fixed amount of time [16]. For example, reallocating time from SB or light PA (LPA) to MVPA was positively associated with quality of life in older adults [17] and middle-aged Japanese adults [18].…”

Body composition impact on sleep in young adults: The mediating role of sedentariness, physical activity, and diet

“…Our study therefore has significant contributions to the clinical and research practice in this field, further clarifying the recognised bidirectional relationship between obesity and sleep disorders [9] and, thus, supporting the need of designing appropriate strategies of health promotion through physical activity and/or sedentary behaviour avoidance in young populations. In this regard, the replacement of sedentary time with physical activity may be the most effective strategy for general sleep and cardiometabolic benefits [68,69]. As sedentariness has also been independently linked to cardiovascular disease, cancer incidence and mortality, and all-cause mortality in adults [70], modifying this behavioural risk factor could not only improve the current obesity and sleep disorder epidemics in young adults but also prevent this population from suffering chronic health conditions and early mortality.…”

Efeito da substituição do tempo de tela e atividades físicas no lazer na percepção positiva de saúde de universitários

“…Para realização da análise de substituição isotemporal, foi realizada a normalização do tempo de prática por uma determinada constante de tempo 14 , pois essa abordagem consiste em remover o tempo de uma atividade por outra, por exemplo, realocando 30 minutos do tempo de caminhada para o tempo de comportamento sedentário, visando esclarecer o efeito do comportamento sedentário sob determinada variável desfecho 21,22 .…”

“…Também torna-se relevante compreender o impacto da realocação do tempo destinado entre diferentes modalidades praticadas no lazer sobre a autoavaliação de saúde, pois essas atividades incidem diretamente em melhorias na aptidão física relacionada à saúde 13 . Deste modo, modelos de análise que permitam estimar o efeito da substituição do tempo dedicado a um determinado comportamento, pelo mesmo tempo dedicado a outro, pode ser útil para a saúde pública 14 .…”