The cost of inaction on physical inactivity to public health-care systems: a population-attributable fraction analysis.

BACKGROUND: Physical inactivity is an important modifiable risk factor for non-communicable diseases (NCDs) and mental health conditions. We aimed to estimate the public health-care costs associated with these diseases because of physical inactivity, which will help policy makers to prioritise investment in policy actions to promote and enable more people to be more active. METHODS: We used a population-attributable fraction formula to estimate the direct public health-care costs of NCDs and mental health conditions for 2020-30. The disease outcomes that we included were incident cases of coronary heart disease, stroke, type 2 diabetes, hypertension, cancer (breast, colon, bladder, endometrial, oesophageal, gastric, and renal), dementia, and depression in adults aged at least 18 years. We used the most recent health and economic data evidence available for 194 countries. FINDINGS: 499·2 million new cases of preventable major NCDs would occur globally by 2030 if the prevalence of physical inactivity does not change, with direct health-care costs of INT$520 billion. The global cost of inaction on physical inactivity would reach approximately $47·6 billion per year. Although 74% of new cases of NCDs would occur in low-income and middle-countries, high-income countries would bear a larger proportion (63%) of the economic costs. The cost of treatment and management of NCDs varied-although dementia accounted for only 3% of new preventable NCDs, the disease corresponded to 22% of all costs; type 2 diabetes accounted for 2% of new preventable cases but 9% of all costs; and cancers accounted for 1% of new preventable cases but 15% of all costs. INTERPRETATION: This health and economic burden of physical inactivity is avoidable. Further investments in and implementation of known and effective policy interventions will support countries to reach the Sustainable Development Goal of reduction of NCD mortality by 2030. FUNDING: None.

Ecological correlates of sport and exercise participation among Thai adolescents: A hierarchical examination of a cross-sectional population survey.

BACKGROUND: Understanding factors influencing adolescents' sport/exercise participation (S/EP) is vital to developing effective interventions, but currently, evidence from less developed countries is limited. The purpose of this study was to examine correlates of S/EP across individual, interpersonal, and environmental levels in a nationally representative sample of Thai adolescents. METHODS: Data from 4617 Thai adolescents aged 14-17 years old were obtained from recruited schools across Thailand. Data on S/EP (outcome variable), and psychosocial, home, and community environment covariates were collected from individual adolescents using the Thailand Physical Activity Children Survey, Student Questionnaire. School environmental data were collected at the school level using a School Built Environment Audit. Hierarchical regressions taking into account school clustering effects were applied for data analysis. RESULTS: At the individual level, age and body mass index were independently and strongly correlated with S/EP. Adolescents with high preference for physical activity (PA) (odd ratio (OR) = 1.71, p < 0.001) and at least a moderate level of self-efficacy (OR = 1.33, p = 0.001) were more likely to have high S/EP. At the interpersonal level, adolescents whose parents joined their sports/exercise at least 1-2 times/week (OR = 1.36, p = 0.003) received ≥3 types of parental support (OR = 1.43, p = 0.005) and who received siblings' (OR = 1.26, p = 0.004) and friends' (OR = 1.99, p < 0.001) support had a greater chance of high S/EP. At the environmental level, adolescents' S/EP was greater when there were at least 3-4 pieces of home sport/exercise equipment (OR = 2.77, p = 0.003), grass areas at school (OR = 1.56, p < 0.001), and at least 1-2 PA facilities in the community (OR = 1.30, p = 0.009). CONCLUSION: Multiple factors at different levels within an ecological framework influencing Thai adolescents' S/EP were generally similar to those found in developed countries, despite some differences. For those interested in promoting and supporting Thai adolescents' engagement in sports/exercise, further exploration of the influence of self-efficacy and attitude toward PA is required at the individual level; parental and peer support at the interpersonal level; and home sport equipment, school grass areas, and neighborhood PA facilities at the environment level.

Economic evaluations of fall prevention exercise programs: a systematic review.

OBJECTIVE: To investigate cost-effectiveness and costs of fall prevention exercise programmes for older adults. DESIGN: Systematic review. DATA SOURCES: Medline, Embase, Web of Science, Scopus, National Institute for Health Research Economic Evaluation Database, Health Technology Assessment database, Tufts Cost-Effectiveness Analysis Registry, Research Papers in Economics and EconLit (inception to May 2022). ELIGIBILITY CRITERIA FOR STUDY SELECTION: Economic evaluations (trial-based or model-based) and costing studies investigating fall prevention exercise programmes versus no intervention or usual care for older adults living in the community or care facilities, and reporting incremental cost-effectiveness ratio (ICER) for fall-related outcomes or quality-adjusted life years (QALY, expressed as cost/QALY) and/or intervention costs. RESULTS: 31 studies were included. For community-dwelling older adults (21 economic evaluations, 6 costing studies), results ranged from more effective and less costly (dominant) interventions up to an ICER of US$279 802/QALY gained and US$11 986/fall prevented (US$ in 2020). Assuming an arbitrary willingness-to-pay threshold (US$100 000/QALY), most results (17/24) were considered cost-effective (moderate certainty). The greatest value for money (lower ICER/QALY gained and fall prevented) appeared to accrue for older adults and those with high fall risk, but unsupervised exercise appeared to offer poor value for money (higher ICER/QALY). For care facilities (two economic evaluations, two costing studies), ICERs ranged from dominant (low certainty) to US$35/fall prevented (moderate certainty). Overall, intervention costs varied and were poorly reported. CONCLUSIONS: Most economic evaluations investigated fall prevention exercise programmes for older adults living in the community. There is moderate certainty evidence that fall prevention exercise programmes are likely to be cost-effective. The evidence for older adults living in care facilities is more limited but promising. PROSPERO REGISTRATION NUMBER: PROSPERO 2020 CRD42020178023.

Economic evaluation of physical activity mass media campaigns across the globe: a systematic review.

BACKGROUND: Physical activity mass media campaigns can deliver physical activity messages to many people, but it remains unclear whether they offer good value for money. We aimed to investigate the cost-effectiveness, cost-utility, and costs of physical activity mass media campaigns. METHODS: A search for economic evaluations (trial- or model-based) and costing studies of physical activity mass media campaigns was performed in six electronic databases (June/2021). The authors reviewed studies independently. A GRADE style rating was used to assess the overall certainty of each modelled economic evaluation. Results were summarised via narrative synthesis. RESULTS: Twenty-five studies (five model-based economic evaluations and 20 costing studies) were included, and all were conducted in high-income countries except for one costing study that was conducted in a middle-income country. The methods and assumptions used in the model-based analyses were highly heterogeneous and the results varied, ranging from the intervention being more effective and less costly (dominant) in two models to an incremental cost of US$130,740 (2020 base year) per QALY gained. The level of certainty of the models ranged from very low (n = 2) to low (n = 3). Overall, intervention costs were poorly reported. CONCLUSIONS: There are few economic evaluations of physical activity mass media campaigns available. The level of certainty of the models was judged to be very low to low, indicating that we have very little to little confidence that the results are reliable for decision making. Therefore, it remains unclear to what extent physical activity mass media campaigns offer good value for money. Future economic evaluations should consider selecting appropriate and comprehensive measures of campaign effectiveness, clearly report the assumptions of the models and fully explore the impact of assumptions in the results. REVIEW REGISTRATION: https://bit.ly/3tKSBZ3.

Impact of physical activity programs and services for older adults: a rapid review.

BACKGROUND: Knowledge of which physical activity programs are most effective for older adults in different sub-populations and contexts is limited. The objectives of this rapid review were to: 1) Overview evidence evaluating physical activity programs/services for older adults; and 2) Describe impact on physical activity, falls, intrinsic capacity (physical domain), functional ability (physical, social, and cognitive/emotional domains), and quality of life. METHODS: We conducted a rapid review of primary studies from 350 systematic reviews identified in a previous scoping review (March 2021: PEDro, MEDLINE, CINAHL, Cochrane Database). For Objective 1, we included intervention studies investigating physical activity programs/services in adults ≥ 60 years. Of these, we included good quality (≥ 6/10 PEDro scale) randomised controlled trials (RCTs) with ≥ 50 participants per group in Objective 2. RESULTS: Objective 1: Of the 1421 intervention studies identified from 8267 records, 79% were RCTs, 87% were in high income countries and 39% were good quality. Objective 2: We identified 87 large, good quality RCTs (26,861 participants). Overall activity promotion, structured exercise and recreation/sport had positive impacts (≥ 50% between-group comparisons positive) across all outcome domains. For overall activity promotion (21 intervention groups), greatest impacts were on physical activity (100% positive) and social outcomes (83% positive). Structured exercise (61 intervention groups) had particularly strong impacts on falls (91% positive), intrinsic capacity (67% positive) and physical functioning (77% positive). Recreation/sport (24 intervention groups) had particularly strong impacts on cognitive/emotional functioning (88% positive). Multicomponent exercise (39 intervention groups) had strong impacts across all outcomes, particularly physical activity (95% positive), falls (90% positive) and physical functioning (81% positive). Results for different populations and settings are presented. CONCLUSION: Evidence supporting physical activity for older adults is positive. We outline which activity types are most effective in different populations and settings.

A scoping review of physical activity interventions for older adults.

BACKGROUND: To inform implementation and future research, this scoping review investigates the volume of evidence for physical activity interventions among adults aged 60+. Our research questions are: (1) what is the evidence regarding interventions designed to increase total physical activity in adults aged 60+ years, in accordance with three of the four strategic objectives of GAPPA (active societies, active environments, active people); (2) what is the current evidence regarding the effectiveness of physical activity programmes and services designed for older adults?; and (3) What are the evidence gaps requiring further research? METHODS: We searched PEDro, MEDLINE, CINAHL and Cochrane from 1 January 2010 to 1 November 2020 for systematic reviews and meta-analyses of physical activity interventions in adults aged 60+. We identified interventions designed to: (1) increase physical activity; and (2) deliver physical activity programmes and services in home, community or outpatient settings. We extracted and coded data from eligible reviews according to our proposed framework informed by TIDieR, Prevention of Falls Network Europe (PROFANE), and WHO's International Classification of Functioning, Disability and Health (ICF). We classified the overall findings as positive, negative or inconclusive. RESULTS: We identified 39 reviews of interventions to increase physical activity and 342 reviews of programmes/services for older adults. Interventions were predominantly structured exercise programmes, including balance strength/resistance training, and physical recreation, such as yoga and tai chi. There were few reviews of health promotion/coaching and health professional education/referral, and none of sport, workplace, sociocultural or environmental interventions. Fewer reported outcomes of total physical activity, social participation and quality of life/well-being. We noted insufficient coverage in diverse and disadvantaged samples and low-middle income countries. CONCLUSIONS: There is a modest but growing volume of evidence regarding interventions designed to increase total physical activity in older adults, although more interventional studies with long term follow-up are needed, particularly for GAPPA 1. Active Societies and GAPPA 2. Active Environments. By comparison, there is abundant evidence for GAPPA 3. specific programmes and services, but coverage of sport and workplace interventions, and diverse samples and settings is lacking. Comprehensive reviews of individual studies are now needed as well as research targeting neglected outcomes, populations and settings.

The First Global Physical Activity and Sedentary Behavior Guidelines for People Living With Disability.

BACKGROUND: The World Health Organization has released the first global public health guidelines on physical activity and sedentary behavior for people living with disability. This paper presents the guidelines, related processes, and evidence, and elaborates upon how the guidelines can support inclusive policy, practice, and research. METHODS: Methods were consistent with the World Health Organization protocols for developing guidelines. Systematic reviews of the evidence on physical activity for health for people living with disability were appraised, along with a consideration of the evidence used to inform the general 2020 World Health Organization guidelines. RESULTS: Evidence supported the development of recommendations for people living with disability, stressing that there are no major risks to engaging in physical activity appropriate to an individual's current activity level, health status, and physical function, and that the health benefits accrued generally outweigh the risks. They also emphasize the benefits of limiting sedentary behavior. CONCLUSIONS: The guidelines mark a positive step forward for disability inclusion, but considerable effort is needed to advance the agenda. This paper highlights key considerations for the implementation of the new recommendations for people living with disability, in line with the human rights agenda underpinning the Global Action Plan on Physical Activity 2018-2030 and allied policies.

School policies and practices associated with Thai children's overall and domain specific physical activity.

School has a significant role in providing opportunities for children to engage in physical activity (PA) through policies and practices. This study aimed to identify the prevalence of school policies and practices related to physical activity (PA) and their association with Thai students' overall and domain specific PA. This cross-sectional analysis included 5,830 students aged 6-17 years from 136 schools recruited though a multi-stage stratified cluster sampling across Thailand. Student's PA data were assessed using a student survey and school data were collected by a principal survey. Associations between students' PA and school variables were examined using logistic regressions. Despite a high prevalence of Thai schools reporting many policies and practices promoting PA in different areas, students reported low levels of PA. None of the school PA policies and practices was associated with students' overall and domain specific activities, with active transport as the one exception. When schools had an active transport policy, students were 40% (OR = 1.40, p = 0.01) more likely to travel actively to/from school. The identified positive relationship between school active transport policy and students' active travel behavior suggests a potential wider adoption of the policy promoting school active transport aiming to increase student's PA levels among all Thai schools. Intervention studies are necessary to confirm this finding. Our study also reflected that, for greater levels of children's school-based PA, strategies to translate the existing school PA policies into effective implementation should be an emphasis for Thai schools.

Air pollution, physical activity and health: A mapping review of the evidence.

BACKGROUND: Exposure to air pollution and physical inactivity are both significant risk factors for non-communicable diseases (NCDs). These risk factors are also linked so that the change in exposure in one will impact risks and benefits of the other. These links are well captured in the active transport (walking, cycling) health impact models, in which the increases in active transport leading to increased inhaled dose of air pollution. However, these links are more complex and go beyond the active transport research field. Hence, in this study, we aimed to summarize the empirical evidence on the links between air pollution and physical activity, and their combined effect on individual and population health. OBJECTIVES AND METHODS: We conducted a non-systematic mapping review of empirical and modelling evidence of the possible links between exposure to air pollution and physical activity published until Autumn 2019. We reviewed empirical evidence for the (i) impact of exposure to air pollution on physical activity behaviour, (ii) exposure to air pollution while engaged in physical activity and (iii) the short-term and (iv) long-term health effects of air pollution exposure on people engaged in physical activity. In addition, we reviewed (v) public health modelling studies that have quantified the combined effect of air pollution and physical activity. These broad research areas were identified through expert discussions, including two public events performed in health-related conferences. RESULTS AND DISCUSSION: The current literature suggests that air pollution may decrease physical activity levels during high air pollution episodes or may prevent people from engaging in physical activity overall in highly polluted environments. Several studies have estimated fine particulate matter (PM2.5) exposure in active transport environment in Europe and North-America, but the concentration in other regions, places for physical activity and for other air pollutants are poorly understood. Observational epidemiological studies provide some evidence for a possible interaction between air pollution and physical activity for acute health outcomes, while results for long-term effects are mixed with several studies suggesting small diminishing health gains from physical activity due to exposure to air pollution for long-term outcomes. Public health modelling studies have estimated that in most situations benefits of physical activity outweigh the risks of air pollution, at least in the active transport environment. However, overall evidence on all examined links is weak for low- and middle-income countries, for sensitive subpopulations (children, elderly, pregnant women, people with pre-existing conditions), and for indoor air pollution. CONCLUSIONS: Physical activity and air pollution are linked through multiple mechanisms, and these relations could have important implications for public health, especially in locations with high air pollution concentrations. Overall, this review calls for international collaboration between air pollution and physical activity research fields to strengthen the evidence base on the links between both and on how policy options could potentially reduce risks and maximise health benefits.

Global Public Health Guidelines on Physical Activity and Sedentary Behavior for People Living With Chronic Conditions: A Call to Action.

BACKGROUND: In 2020, the World Health Organization (WHO) released global guidelines on physical activity (PA) and sedentary behavior, for the first time providing population-based recommendations for people living with selected chronic conditions. This article briefly presents the guidelines, related processes and evidence, and, importantly, considers how they may be used to support research, practice, and policy. METHODS: A brief overview of the scope, agreed methods, selected chronic conditions (adults living with cancer, hypertension, type 2 diabetes, and human immunodeficiency virus), and appraisal of systematic review evidence on PA/sedentary behavior is provided. Methods were consistent with World Health Organization protocols for developing guidelines. RESULTS: Moderate to high certainty evidence (varying by chronic condition and outcome examined) supported that PA can reduce the risk of disease progression or premature mortality and improve physical function and quality of life in adults living with chronic conditions. Direct evidence on sedentary behavior was lacking; however, evidence extrapolated from adult populations was considered applicable, safe, and likely beneficial (low certainty due to indirectness). CONCLUSIONS: Clinical and public health professionals and policy makers should promote the World Health Organization 2020 global guidelines and develop and implement services and programs to increase PA and limit sedentary behavior in adults living with chronic conditions.

Advancing the global physical activity agenda: recommendations for future research by the 2020 WHO physical activity and sedentary behavior guidelines development group.

BACKGROUND: In July, 2019, the World Health Organization (WHO) commenced work to update the 2010 Global Recommendations on Physical Activity for Health and established a Guideline Development Group (GDG) comprising expert public health scientists and practitioners to inform the drafting of the 2020 Guidelines on Physical Activity and Sedentary Behavior. The overall task of the GDG was to review the scientific evidence and provide expert advice to the WHO on the amount of physical activity and sedentary behavior associated with optimal health in children and adolescents, adults, older adults (> 64 years), and also specifically in pregnant and postpartum women and people living with chronic conditions or disabilities. METHODS: The GDG reviewed the available evidence specific to each sub-population using systematic protocols and in doing so, identified a number of gaps in the existing literature. These proposed research gaps were discussed and verified by expert consensus among the entire GDG. RESULTS: Evidence gaps across population sub-groups included a lack of information on: 1) the precise shape of the dose-response curve between physical activity and/or sedentary behavior and several of the health outcomes studied; 2) the health benefits of light-intensity physical activity and of breaking up sedentary time with light-intensity activity; 3) differences in the health effects of different types and domains of physical activity (leisure-time; occupational; transportation; household; education) and of sedentary behavior (occupational; screen time; television viewing); and 4) the joint association between physical activity and sedentary time with health outcomes across the life course. In addition, we acknowledge the need to conduct more population-based studies in low- and middle-income countries and in people living with disabilities and/or chronic disease, and to identify how various sociodemographic factors (age, sex, race/ethnicity, socioeconomic status) modify the health effects of physical activity, in order to address global health disparities. CONCLUSIONS: Although the 2020 WHO Guidelines for Physical Activity and Sedentary Behavior were informed by the most up-to-date research on the health effects of physical activity and sedentary time, there is still substantial work to be done in advancing the global physical activity agenda.

World Health Organization 2020 guidelines on physical activity and sedentary behaviour.

OBJECTIVES: To describe new WHO 2020 guidelines on physical activity and sedentary behaviour. METHODS: The guidelines were developed in accordance with WHO protocols. An expert Guideline Development Group reviewed evidence to assess associations between physical activity and sedentary behaviour for an agreed set of health outcomes and population groups. The assessment used and systematically updated recent relevant systematic reviews; new primary reviews addressed additional health outcomes or subpopulations. RESULTS: The new guidelines address children, adolescents, adults, older adults and include new specific recommendations for pregnant and postpartum women and people living with chronic conditions or disability. All adults should undertake 150-300 min of moderate-intensity, or 75-150 min of vigorous-intensity physical activity, or some equivalent combination of moderate-intensity and vigorous-intensity aerobic physical activity, per week. Among children and adolescents, an average of 60 min/day of moderate-to-vigorous intensity aerobic physical activity across the week provides health benefits. The guidelines recommend regular muscle-strengthening activity for all age groups. Additionally, reducing sedentary behaviours is recommended across all age groups and abilities, although evidence was insufficient to quantify a sedentary behaviour threshold. CONCLUSION: These 2020 WHO guidelines update previous WHO recommendations released in 2010. They reaffirm messages that some physical activity is better than none, that more physical activity is better for optimal health outcomes and provide a new recommendation on reducing sedentary behaviours. These guidelines highlight the importance of regularly undertaking both aerobic and muscle strengthening activities and for the first time, there are specific recommendations for specific populations including for pregnant and postpartum women and people living with chronic conditions or disability. These guidelines should be used to inform national health policies aligned with the WHO Global Action Plan on Physical Activity 2018-2030 and to strengthen surveillance systems that track progress towards national and global targets.

How can global physical activity surveillance adapt to evolving physical activity guidelines? Needs, challenges and future directions.

Public health guidelines on physical activity (PA) establish national policy agendas and provide the basis for setting goals and targets. Advances in measurement and resulting new scientific findings lead to evolution of PA guidelines. PA surveillance serves to track compliance with national guidelines, usually expressed as the proportion of the population 'meeting' the main quantitative guidelines. The WHO recently completed a process to review and update the global PA guidelines. Changes to the guidelines, such as removal of a 10-min bout criterion, pose challenges for PA surveillance. We review the evolution of PA guidelines and associated surveillance methods and explore implications of the updated guidelines for changes in population surveillance and opportunities for technological approaches to PA to enhance surveillance.

Levels of domain-specific physical activity at work, in the household, for travel and for leisure among 327 789 adults from 104 countries.

OBJECTIVE: To compare the country-level absolute and relative contributions of physical activity at work and in the household, for travel, and during leisure-time to total moderate-to-vigorous physical activity (MVPA). METHODS: We used data collected between 2002 and 2019 from 327 789 participants across 104 countries and territories (n=24 low, n=34 lower-middle, n=30 upper-middle, n=16 high-income) from all six World Health Organization (WHO) regions. We calculated mean min/week of work/household, travel and leisure MVPA and compared their relative contributions to total MVPA using Global Physical Activity Questionnaire data. We compared patterns by country, sex and age group (25-44 and 45-64 years). RESULTS: Mean MVPA in work/household, travel and leisure domains across the 104 countries was 950 (IQR 618-1198), 327 (190-405) and 104 (51-131) min/week, respectively. Corresponding relative contributions to total MVPA were 52% (IQR 44%-63%), 36% (25%-45%) and 12% (4%-15%), respectively. Work/household was the highest contributor in 80 countries; travel in 23; leisure in just one. In both absolute and relative terms, low-income countries tended to show higher work/household (1233 min/week, 57%) and lower leisure MVPA levels (72 min/week, 4%). Travel MVPA duration was higher in low-income countries but there was no obvious pattern in the relative contributions. Women tended to have relatively less work/household and more travel MVPA; age groups were generally similar. CONCLUSION: In the largest domain-specific physical activity study to date, we found considerable country-level variation in how MVPA is accumulated. Such information is essential to inform national and global policy and future investments to provide opportunities to be active, accounting for country context.

2020 WHO guidelines on physical activity and sedentary behaviour for children and adolescents aged 5-17 years: summary of the evidence.

BACKGROUND: The World Health Organization (WHO) released in 2020 updated global guidelines on physical activity and sedentary behaviour for children, adolescents, adults, older adults and sub-populations such as pregnant and postpartum women and those living with chronic conditions or disabilities. OBJECTIVE: To summarize the evidence on the associations between physical activity, sedentary behaviour, and health-related outcomes used to inform the 2020 WHO guidelines on physical activity and sedentary behaviour for children and adolescents aged 5-17 years. METHODS: The update of the WHO guideline recommendations for children and adolescents utilized and systematically updated the evidence syntheses on physical activity and sedentary behaviour conducted for the 2016 Canadian 24-Hour Movement Guidelines for Children and Youth, the 2019 Australian 24-Hour Movement Guidelines for Children and Young People (5-17 years), and the 2018 Physical Activity Guidelines for Americans, Second Edition. Systematic reviews published from 2017 up to July 2019 that addressed the key questions were identified, and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework was used to rate the certainty of the evidence for the entire body of evidence. RESULTS: The updated literature search yielded 21 relevant systematic reviews. The evidence base reviewed (i.e., existing and new systematic reviews) provided evidence that greater amounts and higher intensities of physical activity as well as different types of physical activity (i.e., aerobic and muscle and bone strengthening activities) are associated with improved health outcomes (primarily intermediate outcomes). There was sufficient evidence to support recommendations on limiting sedentary behaviours, which was not addressed in the 2010 WHO guidelines. However, there is still insufficient evidence available to fully describe the dose-response relationships between physical activity or sedentary behaviour and health outcomes, and whether the associations vary by type or domain of physical activity or sedentary behaviour. CONCLUSIONS: Addressing the identified research gaps will better inform guideline recommendations in children and adolescents, and future work should aim to prioritize these areas of research. In the meantime, investment and leadership is needed to scale up known effective policies and programs aimed at increasing activity in children and adolescents.

New global guidelines on sedentary behaviour and health for adults: broadening the behavioural targets.

BACKGROUND: In 2018, the World Health Organisation (WHO) commenced a program of work to update the 2010 Global Recommendations on Physical Activity for Health, for the first-time providing population-based guidelines on sedentary behaviour. This paper briefly summarizes and highlights the scientific evidence behind the new sedentary behaviour guidelines for all adults and discusses its strengths and limitations, including evidence gaps/research needs and potential implications for public health practice. METHODS: An overview of the scope and methods used to update the evidence is provided, along with quality assessment and grading methods for the eligible new systematic reviews. The literature search update was conducted for WHO by an external team and reviewers used the AMSTAR 2 (Assessment of Multiple Systematic Reviews) tool for critical appraisal of the systematic reviews under consideration for inclusion. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) method was used to rate the certainty (i.e. very low to high) of the evidence. RESULTS: The updated systematic review identified 22 new reviews published from 2017 up to August 2019, 14 of which were incorporated into the final evidence profiles. Overall, there was moderate certainty evidence that higher amounts of sedentary behaviour increase the risk for all-cause, cardiovascular disease (CVD) and cancer mortality, as well as incidence of CVD, cancer, and type 2 diabetes. However, evidence was deemed insufficient at present to set quantified (time-based) recommendations for sedentary time. Moderate certainty evidence also showed that associations between sedentary behaviour and all-cause, CVD and cancer mortality vary by level of moderate-to-vigorous physical activity (MVPA), which underpinned additional guidance around MVPA in the context of high sedentary time. Finally, there was insufficient or low-certainty systematic review evidence on the type or domain of sedentary behaviour, or the frequency and/or duration of bouts or breaks in sedentary behaviour, to make specific recommendations for the health outcomes examined. CONCLUSIONS: The WHO 2020 guidelines are based on the latest evidence on sedentary behaviour and health, along with interactions between sedentary behaviour and MVPA, and support implementing public health programmes and policies aimed at increasing MVPA and limiting sedentary behaviour. Important evidence gaps and research opportunities are identified.