Sedentary behaviour and health with special reference to obesity and fatty liver in early midlife. The Cardiovascular risk in Young Finns Study

Background: Physical inactivity and positive energy balance pose a risk to health. They increase the risk of obesity and associated non-communicable diseases. Recently, also sedentary behaviour has been associated with obesity and non-communicable diseases. Nevertheless, it has been unclear which type of sedentary behaviour is the most harmful. It is also unknown whether the relationship of sedentary behaviour with obesity is truly independent of other factors, for example physical activity and diet. Longitudinal data are limited, and the direction of causality and the mechanism of action are still unknown. Aims: The aim of this study was 1) to identify the type of sedentary behaviour having the strongest association with obesity, 2) to explore the causal relationship of sedentary behaviour and weight increase, and 3) to additionally, investigate the relationship of sedentary behaviour with fatty liver. These were studied in cross-sectional and/or longitudinal settings using data from the Cardiovascular Risk in Young Finns Study. Special emphasis was put on the evaluation of a wide range of other lifestyle factors and risks for obesity and fatty liver. Subjects: 2,060 subjects (aged 33-50 years in 2011, of which 55 % were female) from the Cardiovascular Risk in Young Finns Study participating in follow-ups in 2001, 2007, and 2011. Measures: Self-reported time spent in various types of sedentary behaviour (I), or TV viewing time (I-III). Measured body weight, height and waist circumference (I-III), and genetic variants for high BMI (I). Fasting plasma concentrations of gamma-glutamyltransferase enzyme and triglyceride, calculated Fatty Liver Index (based on gamma-glutamyltransferase and triglyceride concentration, BMI and waist circumference), and the amount of intrahepatic fat measured with ultrasound (III). Self-reported leisure-time physical activity and active commuting, occupational physical activity, energy intake, diet, alcohol consumption, smoking, socioeconomic status, and sleep duration as possible confounders were considered (I-III). Results: TV viewing is the sedentary behaviour type that has the strongest association with obesity. Sedentary behaviour (TV viewing) precedes weight increase, and not the other way around. Sedentary behaviour (TV viewing) is associated with increased risk of fatty liver. Conclusions: Sedentary behaviour (especially high TV viewing time) is associated with increased risks of obesity and fatty liver. Intervention studies are needed to assess whether reduction of TV time would prevent obesity and fatty liver.

Predicting and breaking sedentary behaviour at work

This thesis aimed at designing and developing a system that can a) infer individuals’ need for a break from sedentary behaviour in the workplace, and b) persuade them to take a break through the use of different techniques from persuasive psychology. We postulated three variables, namely, individuals’ posture, stress levels and involvement in their computer mediated activity. We developed and field-studied a system that could infer these using a web camera and a key presses and mouse clicks log. We found that the system could predict posture from viewing depth and stress from the movement detected. We then created a general formula that predicts individuals’ need for a break using only the posture and stress predictors. Once the first objective was set, we built and field-studied a system that used three ways to communicate a recommendation for a break to a user: implicit, just-in time and ambient feedback. The implicit feedback was operationalized through changes in the users’ computer wallpaper that provided subtle visual cues. The just-in time feedback employed prompting at the bottom right side of the user’s screen. In addition, we implemented an intuitive behind-screen interaction technique where people can snooze a notification using simple gestures. The ambient feedback mechanism employed an origami sculpture sitting on the user’s desk. This prototype was continuously reflecting the user’s posture and performed rhythmic movements when to recommend breaks. A field study demonstrated the overall success of the system, with 69% of the break recommendations received by users were accepted. The study further revealed the strengths and weaknesses of the three persuasive mechanisms.

Exploring the relationship between patterns of physical activity, sedentary behaviour and cardiometabolic health in middle-aged Irish adults

Background and Study Rationale Being physically active is a major contributor to both physical and mental health. More specifically, being physically active lowers risk of coronary heart disease, high blood pressure, stroke, metabolic syndrome (MetS), diabetes, certain cancers and depression, and increases cognitive function and wellbeing. The physiological mechanisms that occur in response to physical activity and the impact of total physical activity and sedentary behaviour on cardiometabolic health have been extensively studied. In contrast, limited data evaluating the specific effects of daily and weekly patterns of physical behaviour on cardiometabolic health exist. Additionally, no other study has examined interrelated patterns and minute-by-minute accumulation of physical behaviour throughout the day across week days in middle-aged adults. Study Aims The overarching aims of this thesis are firstly to describe patterns of behaviour throughout the day and week, and secondly to explore associations between these patterns and cardiometabolic health in a middle-aged population. The specific objectives are to: 1 Compare agreement between the International Physical Activity Questionnaire-Short Form (IPAQ-SF) and GENEActiv accelerometer-derived moderate-to-vigorous (MVPA) activity and secondly to compare their associations with a range of cardiometabolic and inflammatory markers in middle-aged adults. 2 Determine a suitable monitoring frame needed to reliably capture weekly, accelerometer-measured, activity in our population. 3 Identify groups of participants who have similar weekly patterns of physical behaviour, and determine if underlying patterns of cardiometabolic profiles exist among these groups. 4 Explore the variation of physical behaviour throughout the day to identify whether daily patterns of physical behaviour vary by cardiometabolic health. Methods All results in this thesis are based on data from a subsample of the Mitchelstown Cohort; 475 (46.1% males; mean aged 59.7±5.5 years) middle-aged Irish adults. Subjective physical activity levels were assessed using the IPAQ-SF. Participants wore the wrist GENEActiv accelerometer for 7 consecutive days. Data was collected at 100Hz and summarised into a signal magnitude vector using 60s epochs. Each time interval was categorised based on validated cut-offs. Data on cardiometabolic and inflammatory markers was collected according to standard protocol. Cardiometabolic outcomes (obesity, diabetes, hypertension and MetS) were defined according to internationally recognised definitions by World Health Organisation (WHO) and Irish Diabetes Federation (IDF). Results The results of the first chapter suggest that the IPAQ-SF lacks the sensitivity to assess patterning of activity and guideline adherence and assessing the relationship with cardiometabolic and inflammatory markers. Furthermore, GENEActiv accelerometer-derived MVPA appears to be better at detecting relationships with cardiometabolic and inflammatory markers. The second chapter examined variations in day-to-day physical behaviour levels between- and within-subjects. The main findings were that Sunday differed from all other days in the week for sedentary behaviour and light activity and that a large within-subject variation across days of the week for vigorous activity exists. Our data indicate that six days of monitoring, four weekdays plus Saturday and Sunday, are required to reliably estimate weekly habitual activity in all activity intensities. In the next chapter, latent profile analysis of weekly, interrelated patterns of physical behaviour identified four distinct physical behaviour patterns; Sedentary Group (15.9%), Sedentary; Lower Activity Group (28%), Sedentary; Higher Activity Group (44.2%) and a Physically Active Group (11.9%). Overall the Sedentary Group had poorer outcomes, characterised by unfavourable cardiometabolic and inflammatory profiles. The remaining classes were characterised by healthier cardiometabolic profiles with lower sedentary behaviour levels. The final chapter, which aimed to compare daily cumulative patterns of minute-by-minute physical behaviour intensities across those with and without MetS, revealed significant differences in weekday and weekend day MVPA. In particular, those with MetS start accumulating MVPA later in the day and for a shorted day period. Conclusion In conclusion, the results of this thesis add to the evidence base regards an optimal monitoring period for physical behaviour measurement to accurately capture weekly physical behaviour patterns. In addition, the results highlight whether weekly and daily distribution of activity is associated with cardiometabolic health and inflammatory profiles. The key findings of this thesis demonstrate the importance of daily and weekly physical behaviour patterning of activity intensity in the context of cardiometabolic health risk. In addition, these findings highlight the importance of using physical behaviour patterns of free-living adults observed in a population-based study to inform and aid health promotion activity programmes and primary care prevention and treatment strategies and development of future tailored physical activity based interventions.

Performance analysis of an SRI screen based on employment quality in high and low capital industries: International evidence

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Finance from the NOVA – School of Business and Economics and Maastricht University School of Business and Economics

Regional differences of physical activity and sedentary behaviour in Swiss children are not explained by socio-demographics or the built environment.

OBJECTIVE: We evaluated whether regional differences in physical activity (PA) and sedentary behaviour (SB) existed along language boundaries within Switzerland and whether potential differences would be explained by socio-demographics or environmental characteristics. METHODS: We combined data of 611 children aged 4 to 7 years from four regional studies. PA and SB were assessed by accelerometers. Information about the socio-demographic background was obtained by questionnaires. Objective neighbourhood attributes could be linked to home addresses. Multivariate regression models were used to test associations between PA and SB and socio-demographic characteristics and neighbourhood attributes. RESULTS: Children from the German compared to the French-speaking region were more physically active and less sedentary (by 10-15 %, p < 0.01). Although German-speaking children lived in a more favourable environment and a higher socioeconomic neighbourhood (differences p < 0.001), these characteristics did not explain the differences in PA behaviour between French and German speaking. CONCLUSIONS: Factors related to the language region, which might be culturally rooted were among the strongest correlates of PA and SB among Swiss children, independent of individual, social and environmental factors.

Regional differences of physical activity and sedentary behaviour in Swiss children are not explained by socio-demographics or the built environment

Objective We evaluated whether regional differences in physical activity (PA) and sedentary behaviour (SB) existed along language boundaries within Switzerland and whether potential differences would be explained by socio-demographics or environmental characteristics. Methods We combined data of 611 children aged 4 to 7 years from four regional studies. PA and SB were assessed by accelerometers. Information about the socio-demographic background was obtained by questionnaires. Objective neighbourhood attributes could be linked to home addresses. Multivariate regression models were used to test associations between PA and SB and socio-demographic characteristics and neighbourhood attributes. Results Children from the German compared to the French-speaking region were more physically active and less sedentary (by 10–15 %, p < 0.01). Although German-speaking children lived in a more favourable environment and a higher socioeconomic neighbourhood (differences p < 0.001), these characteristics did not explain the differences in PA behaviour between French and German speaking. Conclusions Factors related to the language region, which might be culturally rooted were among the strongest correlates of PA and SB among Swiss children, independent of individual, social and environmental factors.

Normative reference values for the 20-meter shuttlerun test in a population-based sample of schoolchildren in Bogota, Colombia: The FUPRECOL Study

Our aim was to determine the normative reference values of cardiorespiratory fitness (CRF) and to establish the proportion of subjects with low CRF suggestive of future cardio-metabolic risk.

Uptake and factors that influence the use of ‘sit less, move more’ occupational intervention strategies in Spanish office employees

Background Little is known about the types of ‘sit less, move more’ strategies that appeal to office employees, or what factors influence their use. This study assessed the uptake of strategies in Spanish university office employees engaged in an intervention, and those factors that enabled or limited strategy uptake. Methods The study used a mixed method design. Semi-structured interviews were conducted with academics and administrators (n = 12; 44 ± 12 mean SD age; 6 women) at three points across the five-month intervention, and data used to identify factors that influenced the uptake of strategies. Employees who finished the intervention then completed a survey rating (n = 88; 42 ± 8 mean SD age; 51 women) the extent to which strategies were used [never (1) to usually (4)]; additional survey items (generated from interviewee data) rated the impact of factors that enabled or limited strategy uptake [no influence (1) to very strong influence (4)]. Survey score distributions and averages were calculated and findings triangulated with interview data. Results Relative to baseline, 67% of the sample increased step counts post intervention (n = 59); 60% decreased occupational sitting (n = 53). ‘Active work tasks’ and ‘increases in walking intensity’ were the strategies most frequently used by employees (89% and 94% sometimes or usually utilised these strategies); ‘walk-talk meetings’ and ‘lunchtime walking groups’ were the least used (80% and 96% hardly ever or never utilised these strategies). ‘Sitting time and step count logging’ was the most important enabler of behaviour change (mean survey score of 3.1 ± 0.8); interviewees highlighted the motivational value of being able to view logged data through visual graphics in a dedicated website, and gain feedback on progress against set goals. ‘Screen based work’ (mean survey score of 3.2 ± 0.8) was the most significant barrier limiting the uptake of strategies. Inherent time pressures and cultural norms that dictated sedentary work practices limited the adoption of ‘walk-talk meetings’ and ‘lunch time walking groups’. Conclusions The findings provide practical insights into which strategies and influences practitioners need to target to maximise the impact of ‘sit less, move more’ occupational intervention strategies.

Niveles de actividad física, condición física y tiempo en pantallas en escolares de Bogotá, Colombia: Estudio FUPRECOL

Examina la relación entre los niveles de actividad física (AF) de forma objetiva, la condición física (CF) y el tiempo de exposición a pantallas en niños y adolescentes de Bogotá, Colombia.

Conceptos y prácticas de la actividad física que se reproducen en las clases sociales: aproximación desde el enfoque determinantes/ determinación social de la salud

El concepto de actividad física es concebido de diferentes formas. Mostrando que existen varios factores que afectan de manera directa e indirecta la percepción que los sujetos construyen entorno a él, generando así una aproximación a diferentes definiciones de la actividad física desde varias perspectivas y dimensiones, donde predomina una noción netamente biológica. Este estudio pretende analizar, como desde las clases sociales se concibe la actividad física en sus conceptos y prácticas considerando los modelos de determinantes y determinación social para la salud. Con fin de comprender como los autores de la literatura científica conciben la actividad física y la relación con las clases sociales, desde una perspectiva teórica de los determinantes sociales de la salud y la teoría de la determinación social, se realizó una revisión documental y análisis de contenido de los conceptos y prácticas de la actividad física que se han considerado en los últimos 10 años. Para ello se seleccionaron las bases de datos PubMed y BVS (Biblioteca Virtual de Salud) por sus énfasis en publicaciones de salud mundialmente. Mostrando que la actividad física es concebida dominantemente desde una perspectiva biológica que ejerce una mirada reduccionista. Las relaciones entre actividad física y las clases sociales están claramente establecidas, sin embargo, estas relaciones pueden discrepar teniendo en cuenta el concepto de clase social, el contexto y la orientación de los autores y las poblaciones objetos de estudio. Obteniendo como resultado que los estudios documentados, revisados y analizados muestran una clara tendencia al modelo de determinantes; no obstante, algunos estudios en sus análisis se orientan hacia el modelo de determinación social. En cuanto al concepto de clases sociales los autores consideran una combinación de factores culturales y económicos sin atreverse a adoptar un concepto específico.

The effects of Australian tall poppy attitudes on American value based leadership theory

A survey study of twenty-two Australian CEOs and their subordinates assessed relationships between Australian leader motives, Australian value based leader behaviour, subordinate tall poppy attitudes and subordinate commitment, effectiveness, motivation and satisfaction (CEMS). On the whole, the results showed general support for value based leadership processes. Subsequent regression analyses of the second main component of Value Based Leadership Theory, value based leader behaviour, revealed that the collectivistic, inspirational, integrity and visionary behaviour sub-scales of the construct were positively related with subordinate CEMS. Although the hypothesis that subordinate tall poppy attitudes would moderate value based leadership processes was not clearly supported, subsequent regression analyses found that subordinate tall poppy attitudes were negatively related with perceptions of value based leader behaviour and CEMS. These findings suggest complex relationships between the three constructs, and the proposed model for the Australian context is accordingly amended. Overall, the research supports the need to consider cultural-specific attitudes in management development.

Physical activity and pregnancy

SUMMARY : The traditional medical advice for pregnant women has been to reduce their physical activity (PA) levels. The advice was based on concerns that exercise could affect pregnancy outcomes by increasing core body temperature, by increasing the risk of maternal musculoskeletal injury and by altering the transplacental transport of oxygen and nutrients to maternal skeletal muscle rather than to the developing foetus. In the meantime, several studies have provided new information on adaptation of the pregnant woman and her foetus to moderate PA. New investigations have shown no adverse maternal or neonatal outcomes, abnormal foetal growth, increase in early pregnancy loss, or late pregnancy complications. Moreover, enrolment in moderate PA has proven to result in marked health benefits including improved maternal cardiovascular function, reduction of excessive weight gain and fat retention, less complicated labour, improved foetal stress tolerance and neurobehavioral maturation. In view of the beneficial effects, current recommendations encourage healthy pregnant women to engage in 30 minutes of moderate PA on most, if not all, days of the week. This thesis work addressed several questions. Firstly, it examined whether compliance with the recommended levels of PA during pregnancy results in better preparedness for the sudden physical exertion of labour and delivery. Secondly, it measured PA during pregnancy as compared to postpartum. Lastly, it assessed the influence of pre-pregnancy body mass index on gestational resting metabolic rate. Data collection was conducted on healthy women living in Switzerland during the third trimester of pregnancy and postpartum. Total and activity energy expenditure was assessed through 24-hour heart rate and accelerations recordings, and cardiovascular fitness through an individual step-test. Information related to pregnancy, labour and delivery was collected from medical records. The results indicate that a minimum 30 min of moderate PA per day during pregnancy are associated with better cardiovascular fitness and lower risk of operative delivery with no negative effects on maternal and foetal conditions (study 1). Despite these benefits, a substantial proportion of pregnant women (39%) living in Switzerland do not meet the PA recommendations. The decrease in activity related energy expenditure during pregnancy compared to postpartum was measured to be around 100 kcal/day (~13%), whereas the total energy expenditure was found to increase by 300 kcal/day (study 2). Thus, the energy cost of late pregnancy in Switzerland corresponds to 200 kca/day. These findings are based on average values of the study group. It should be noted, however, that large variations in individual energy expenditure may occur depending on the pre-pregnancy body mass index (study 3). When adjusted to body weight, gestational resting metabolic rate is significantly lower among women of high pre-pregnancy body mass index compared to women of normal or low pre-pregnancy body mass index. This can be explained by the fact that resting metabolic rate is primarily a function of fat-free mass, and when expressed per kg body weight, it decreases as the percentage of body fat increases. If energy intake is not modified appropriately in order to match lower energy cost per kg body weight in overweight and obese women it will result in positive energy balance, thus contributing to the current trend towards increasing adiposity in affluent society. The results of these studies go beyond the current state of knowledge on PA and pregnancy (study 4) and provide valid evidence to guide clinical practice. In view of the current epidemic of sedentary behaviour and obesity related pathology, the findings contribute new and reliable information to public health policies regarding the effects of PA in pregnancy, an important period of life for both mother and infant.

Cost-effectiveness of an exercise intervention program in perimenopausal women: the Fitness League Against MENopause COst (FLAMENCO) randomized controlled trial.

BACKGROUND The high prevalence of women that do not reach the recommended level of physical activity is worrisome. A sedentary lifestyle has negative consequences on health status and increases health care costs. The main objective of this project is to assess the cost-effectiveness of a primary care-based exercise intervention in perimenopausal women. METHODS/DESIGN The present study is a Randomized Controlled Trial. A total of 150 eligible women will be recruited and randomly assigned to either a 16-week exercise intervention (3 sessions/week), or to usual care (control) group. The primary outcome measure is the incremental cost-effectiveness ratio. The secondary outcome measures are: i) socio-demographic and clinical information; ii) body composition; iii) dietary patterns; iv) glycaemic and lipid profile; v) physical fitness; vi) physical activity and sedentary behaviour; vii) sleep quality; viii) quality of life, mental health and positive health; ix) menopause symptoms. All outcomes will be assessed at baseline and post intervention. The data will be analysed on an intention-to-treat basis and per protocol. In addition, we will conduct a cost effectiveness analysis from a health system perspective. DISCUSSION The intervention designed is feasible and if it proves to be clinically and cost effective, it can be easily transferred to other similar contexts. Consequently, the findings of this project might help the Health Systems to identify strategies for primary prevention and health promotion as well as to reduce health care requirements and costs. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT02358109 . Date of registration: 05/02/2015.

Identification, using a siRNA screen approach, and molecular characterization of a new Fas pathway modulator: STK11/

Abstract : Apoptosis is an evolutionarily conserved cellular suicide mechanism that can be triggered by activation of various pathways, such as the Fas-Pathway. Upon stimulation by its specific ligand (FasL), present at the surface of Cytotoxic Τ lymphocytes, the death receptor Fas initiates a signaling cascade culminating in the activation of cellular caspases, leading thus to cell death of the target cell (e.g. transformed cell). Dysregulation of apoptosis in general, and of Fas pathway in particular, was shown to contribute to pathogenesis of cancers and many human diseases. Even though, during the last decades the molecular mechanisms of apoptosis have been widely studied, it is important to better understand the mechanisms leading to apoptosis, to improve our understanding of pathological processes, and generate more subtle apoptosis-modulating therapies to fight cancer and other diseases. In order to identify new components of the Fas signaling pathway, a screen based on the mechanism of RNA interference was undertaken. After a first and a second manual whole-kinome screen, we identified several strong positive hits that showed a protection against Fas ligand-induced apoptosis with distinct siRNAs, notably STK11, an interesting tumor suppressor mutated in several sporadic and inherited cancers. The STK11 functional characterization reveals that this kinase represents an apically acting general pro-apoptotic modulator of the extrinsic pathway (FasL, TRAIL, TNF-induced apoptosis), but not of the intrinsic apoptotic pathway. The STK11 action on the Fas pathway was shown to be dependent on its kinase activity, but independent of AMPK, a well-characterized STK11 downstream substrate. Furthermore, STK11 was shown to interact with caspase-8, a major mediator of the extrinsic pathway, and modulate its activity through an unclear mechanism that may involve an STK11-dependant caspase-8 phosphorylation. This modification may allow a proper caspase-8 polyubiquitination and activation in p62 sequestosmes aggregates, but may also increase the activation of caspase-8 at the DISC level. In addition, we observed that STK11 modulate not only the apoptotic pathway induced by Fas engagement, but also FasL-induced JNK and NF- KB, sustaining an upstream role of this kinase in the pathway. In conclusion, our report reveals that STK11 is an important pro-apoptotic modulator of the Fas pathway in particular, and extrinsic pathway in general. Our finding could explain, at least partially, why inactivating mutations of the kinase leads to cancer, by allowing resistance to apoptosis and accordingly evasion of immune surveillance. Résumé : L'apoptose est un mécanisme de suicide cellulaire, conservé dans diverses espèces, et qui au niveau moléculaire est déclenché par différentes voies de signalisation, comme par exemple lors de l'activation du récepteur Fas. La liaison du ligand FasL au récepteur de la mort Fas, induit une cascade de signalisation qui conduit à l'activation des caspases. Les lymphocytes Τ cytotoxiques peuvent utiliser la voie Fas pour induire la mort et se débarrasser de cellules dangereuses pour le reste de l'organisme, tel que les cellules transformées. La dysrégulation de l'apoptose en général, et de la voie Fas en particulier, peut contribuer à diverses maladies telles que le cancer. Même si ces dernières décennies, les mécanismes moléculaires conduisant à l'apoptose ont été extensivement étudiés, il reste néanmoins important de mieux comprendre le phénomène d'apoptose, pour améliorer notre compréhension des processus pathologiques, mais surtout dans le but de développer de nouvelles thérapies ciblant l'apoptose contre le cancer et d'autres pathologies. Pour identifier de nouveau constituants de la voie Fas, un criblage génétique basé sur l'interférence à l'ARN a été entrepris. Après un premier et un deuxième criblage d'une librairie du kinome, nous avons identifié différentes protéines qui pourraient jouer un rôle positif dans la voie Fas, et en particulier la protéine suppresseur de tumeur STK11, qui est fréquemment mutée dans divers cancers sporadiques et héréditaires. La caractérisation fonctionnelle de STK11 a révélé que cette kinase était un modulateur apical de la voie extrinsèque de l'apoptose en général (Fas, TNF, TRAIL), mais pas de la voie intrinsèque. L'action de STK11 sur la voie Fas est dépendante de sa fonction kinase, mais indépendante de l'AMPK, un substrat bien caractérisé de STK11. De plus, STK11 interagît avec la caspase-8, un constituant majeur de la voie Fas, et module son activité, par un mécanisme encore peu clair qui pourrait impliquer une phosphorylation de la caspase-8 par STK11. Cette modification pourrait permettre une activation optimale de la caspase-8 en jouant un rôle dans le processus de polyubiquitination de la caspase-8, phénomène qui semble être important pour l'activation de la caspase-8 dans des agrégats protéiques avec p62, mais qui pourrait aussi augmenter son activation au niveau du DISC. Finalement, nous avons observé que STK11 modulait non seulement la voie apoptotique déclenchée par l'activation de Fas, mais aussi les voies non-apoptotiques de Fas, comme JNK et NF-KB. En conclusion notre étude, révèle que STK11 est un important modulateur pro- apoptotique de la voie Fas, et de la voie extrinsèque en général. Cette découverte pourrait expliquer, du moins partiellement, pourquoi les mutations inactivatrices de STK11 conduisent au cancer, par une augmentation de la résistance à l'apoptose et donc par l'évasion de la surveillance immunitaire.

Objectively measured physical activity and sedentary time in youth: the International children's accelerometry database (ICAD).

BACKGROUND: Physical activity and sedentary behaviour in youth have been reported to vary by sex, age, weight status and country. However, supporting data are often self-reported and/or do not encompass a wide range of ages or geographical locations. This study aimed to describe objectively-measured physical activity and sedentary time patterns in youth. METHODS: The International Children's Accelerometry Database (ICAD) consists of ActiGraph accelerometer data from 20 studies in ten countries, processed using common data reduction procedures. Analyses were conducted on 27,637 participants (2.8-18.4 years) who provided at least three days of valid accelerometer data. Linear regression was used to examine associations between age, sex, weight status, country and physical activity outcomes. RESULTS: Boys were less sedentary and more active than girls at all ages. After 5 years of age there was an average cross-sectional decrease of 4.2 % in total physical activity with each additional year of age, due mainly to lower levels of light-intensity physical activity and greater time spent sedentary. Physical activity did not differ by weight status in the youngest children, but from age seven onwards, overweight/obese participants were less active than their normal weight counterparts. Physical activity varied between samples from different countries, with a 15-20 % difference between the highest and lowest countries at age 9-10 and a 26-28 % difference at age 12-13. CONCLUSIONS: Physical activity differed between samples from different countries, but the associations between demographic characteristics and physical activity were consistently observed. Further research is needed to explore environmental and sociocultural explanations for these differences.