Sedentary Bouts Research Articles

Sedentary Behaviour Intervention as a Personalised Secondary Prevention Strategy (SIT LESS) for patients with coronary artery disease participating in cardiac rehabilitation: rationale and design of the SIT LESS randomised clinical trial

Patients with coronary artery disease (CAD) are more sedentary compared with the general population, but contemporary cardiac rehabilitation (CR) programmes do not specifically target sedentary behaviour (SB). We developed a...

Device-measured sedentary time in Norwegian children and adolescents in the era of ubiquitous internet access: secular changes between 2005, 2011 and 2018.

BackgroundAccess to screen-based media has been revolutionized during the past two decades. How this has affected sedentary time (ST) accumulation in children is poorly understood.MethodsThis study, based on the Physical Activity among Norwegian Children Study (PANCS), uses accelerometer data from population-based samples of 9- and 15‐year-olds, collected in 2005 (n = 1722), 2011 (n = 1587) and 2018 (n = 1859). Secular changes between surveys were analysed using random-effects linear regression models adjusted for survey-specific factors. Data on ST were collected using hip-worn ActiGraphs and ST was defined using a threshold equivalent to <100 counts/min. Sedentary bouts were grouped by duration: <1, 1–5, 5–15, 15–30 and ≥30 min.ResultsBetween 2005 and 2018, ST increased by 29 min/day in 9-year-old boys (95% CI: 19, 39; P <0.001), by 21 min/day in 15-year-old boys (95% CI: 8, 34; P = 0.002) and by 22 min/day in 15-year-old girls (95% CI: 10, 35; P <0.001), but not in 9-year-old girls at 6 min/day (95% CI: -3, 16; P = 0.191). All age-sex groups accumulated less ST in bouts lasting <5 min and more ST in longer bouts, particularly in 5–15-min bouts. Adolescent girls also increased ST accumulation in 15–30-min and ≥30-min bouts. Changes were largely mirrored before, during and after school on weekdays and during weekend days.ConclusionsCoinciding with the introduction of smartphones, tablets and near-universal internet access, total daily ST and ST accumulated in prolonged sedentary bouts increased between 2005 and 2018 in children and adolescents.

Relation between Prolonged Sedentary Bouts and Health-Related Quality of Life in Patients on Chronic Hemodialysis.

This study aimed to investigate the link between prolonged sedentary bouts and health-related quality of life (QOL) in patients on chronic hemodialysis (CHD). A total of 84 outpatients on CHD, aged 71.6±11.8 years, were enrolled in this cross-sectional study. Parameters for prolonged sedentary bouts [i.e., ≧ 30 min (% and bout) and ≧ 60 min (% and bout)] were measured using a triaxial accelerometer. Health-related QOL (HRQOL) was evaluated by the Euro-QOL (EQ-5D). Clinical parameters were obtained from medical records. Relatively prolonged sedentary bouts (%) were 44.0±18.2 (≧ 30 min) and 29.8±16.5 (≧ 60 min) for total days. Prolonged sedentary bouts (bouts) were 6.2±2.7 (≧ 30 min) and 2.7±1.6 (≧ 60 min) for total days. EQ-5D scores were 0.728±0.220. All prolonged sedentary bout parameters were negatively correlated with EQ-5D scores, except for prolonged sedentary bouts (≧ 60 min) (min) and relatively prolonged sedentary bouts (%) on hemodialysis days. Multiple regression analysis showed that prolonged sedentary bout parameters were an important factor in EQ-5D scores even after adjusting for confounding factors for total and non-hemodialysis days. Our results suggested that prolonged sedentary bouts were closely associated with HRQOL in patients on CHD, especially on non-hemodialysis days.

Cross-Sectional Associations of Sedentary Behavior and Sitting with Serum Lipid Biomarkers in Midlife.

ABSTRACTIntroductionPhysical inactivity, excessive total time spent in sedentary behavior (SB) and prolonged sedentary bouts have been proposed to be risk factors for chronic disease morbidity and mortality worldwide. However, which patterns and postures of SB have the most negative impacts on health outcomes is still unclear. This population-based study aimed to investigate the independent associations of the patterns of accelerometer-based overall SB and sitting with serum lipid biomarkers at different moderate- to vigorous-intensity physical activity (MVPA) levels.MethodsPhysical activity and SB were measured in a birth cohort sample (N = 3272) at 46 yr using a triaxial hip-worn accelerometer in free-living conditions for 14 d. Raw acceleration data were classified into SB and PA using a machine learning–based model, and the bouts of overall SB and sitting were identified from the classified data. The participants also answered health-related questionnaires and participated in clinical examinations. Associations of overall SB (lying and sitting) and sitting patterns with serum lipid biomarkers were investigated using linear regression.ResultsThe overall SB patterns were more consistently associated with serum lipid biomarkers than the sitting patterns after adjustments. Among the participants with the least and the most MVPA, high total time spent in SB and SB bouts of 15–29.99 and ≥30 min were associated with impaired lipid metabolism. Among those with moderate amount of MVPA, higher time spent in SB and SB bouts of 15–29.99 min was unfavorably associated with serum lipid biomarkers.ConclusionsThe associations between SB patterns and serum lipid biomarkers were dependent on MVPA level, which should be considered when planning evidence-based interventions to decrease SB in midlife.

Patterns of Objectively Measured Sedentary Time and Emotional Disorder Symptoms Among Youth.

We examined the within-person longitudinal and bidirectional associations between patterns of sedentary time accumulation [alpha (sedentary bout duration/length), sedentary breaks (number of breaks in sedentary bouts)], and symptoms of major depressive disorder and generalized anxiety disorder. Children [N = 167, 10.1(0.9) years old, 54.5% female, 59.3% Hispanic, 35.9% overweight/obese at baseline] participated in a 3-year longitudinal study that consisted of assessments of sedentary time, and depressive and anxiety symptoms. At each assessment, participants wore accelerometers and completed the Revised Child Anxiety and Depression Scale. Separate random intercept cross-lagged panel models estimated the within-person longitudinal and bidirectional associations between alpha, sedentary breaks, and symptoms of major depressive disorder and generalized anxiety disorder across chronological age intervals. Having greater than one's own usual depressive symptoms at age 11 was associated with fewer sedentary breaks 1 year later. Having greater than one's own usual generalized anxiety symptoms at age 11 was associated with longer sedentary bouts and fewer sedentary breaks 1 year later. In contrast, having greater than one's own usual sedentary breaks at age 10 was associated with fewer generalized anxiety symptoms 1 year later. All other associations, including at younger ages, were null. Deviations from one's usual levels of depressive or anxiety symptoms may be important for how sedentary time is subsequently accumulated. Intraindividual processes appear to be at play, therefore more within-person research is needed. Intervention strategies for promoting a healthier accumulation of sedentary time may consider targeting occasions when depressive and anxiety symptoms are greater than usual.

Sedentary Behavior and Atrial Fibrillation in Older Women: The OPACH Study.

BackgroundSedentary behavior is associated with cardiovascular disease, but its association with incident atrial fibrillation is not well studied. Our aim was to measure the association between objectively measured sedentary behavior and incident atrial fibrillation.Methods and ResultsSedentary behavior was measured by a triaxial accelerometer worn on a belt for 1 week. Incident atrial fibrillation was ascertained from Medicare claims. The associations between total sedentary time (or patterns of sedentary behavior) and incident atrial fibrillation were assessed using Cox proportional hazards models adjusted for demographic and clinical covariates. Among 2675 participants (mean age, 78.2 years), there were 268 (10.0%) cases of incident atrial fibrillation at a rate of 31 cases per 1000 person‐years. Greater total sedentary time was associated with a higher risk of incident atrial fibrillation after adjustment for age, race and ethnicity, body mass index, education, smoking history, hypertension, diabetes, stroke, heart disease, and other chronic conditions (quartile 4 versus quartile 1: hazard ratio, 1.20, [95% CI, 0.81–1.78]; P for trend=0.05). After adjusting for physical function and self‐rated health, this was no longer statistically significant. Both longer mean sedentary bout duration and more continuous sedentary periods (versus frequent breaks in sedentary time) were also associated with higher risks of incident atrial fibrillation, but these associations were also attenuated with serial adjustment.ConclusionsTotal sedentary time and prolonged patterns of sedentary accumulation were associated with a higher risk of atrial fibrillation in this prospective study of community‐dwelling older women, but these associations were attenuated by adjustment for physical function and self‐reported health. This suggests that associations between sedentary behavior and atrial fibrillation may be attributable to global measures of overall function and health.

Impact of habitual sedentary patterns on popliteal artery endothelial-dependent vasodilation in healthy adults.

Introduction:Acute, laboratory-based bouts of prolonged sitting attenuate lower-limb arterial endothelial-dependent vasodilation. However, the impact of habitual sedentary patterns on popliteal artery endothelial health is unclear. We tested the hypothesis that greater habitual total sedentary time, more time spent in prolonged sedentary bouts, and fewer sedentary breaks would be associated with worse popliteal flow-mediated dilation (FMD) responses.Methods:This cross-sectional study used 98 healthy participants (19–77 years, 53 females) that wore an activPAL monitor on the thigh for 6.4 ± 0.8 days to objectively measure sedentary activity and completed a popliteal ultrasound assessment to determine FMD. Both relative (%baseline diameter) and absolute (mm) FMD were calculated. Using bivariate correlation and multiple regression analyses, we examined if there were relationships between sedentary outcomes and FMD while statistically controlling for any potential confounders.Results:In the multiple regression model, age (p = 0.006, β = −0.030, 95% CI = −0.051, −0.009) and total time in sedentary bouts > 1 hour (p = 0.031, β = −0.005, 95% CI = −0.009, −0.001) were independent predictors of relative FMD. Age (β = −0.002, 95% CI = −0.003, −0.001), mean blood flow (β = 0.013, 95% CI = 0.002, 0.024), moderate-intensity physical activity (β = 155.9E−5, 95% CI = 22.4E−5, 289.4E−5), sedentary breaks (β = 0.036, 95% CI = 0.007, 0.066), and total time spent in sedentary bouts > 1 hour (β = −25.02E−5, 95% CI = −47.67E−5, −2.378E−5) were predictors of absolute FMD (all, p < 0.047). All independent outcomes remained significant after partially controlling for all other predictor variables (all, p < 0.031).Conclusions:Habitual prolonged sedentary bouts and sedentary breaks, but not total sedentary time, were predictors of popliteal endothelial-dependent vasodilatory function. The patterns by which sedentary time is accumulated may be more important than the total sedentary time on lower-limb arterial health.

Associations of Objectively-Measured Sedentary Time and Patterns with Cognitive Function in Non-Demented Japanese Older Adults: A Cross-Sectional Study.

This study aimed to investigate the cross-sectional associations of objectively-measured sedentary time and patterns with cognitive function in Japanese older adults. A total of 1681 non-demented community-dwelling older adults (aged 73 ± 6, 62.1% women) were included. Total sedentary time, prolonged sedentary time (accumulated in ≥30 min bouts) and mean sedentary bout length were assessed using a tri-axial accelerometer. Global and domain-specific cognitive functions were measured using the Montreal Cognitive Assessment. The average of total sedentary time and prolonged sedentary time were 462 ± 125 and 186 ± 111 min/day, respectively. Greater prolonged sedentary time, but not total sedentary time, was significantly associated with poorer performance in the orientation domain even after controlling for moderate-to-vigorous physical activity (p for trend = 0.002). A significant inverse association was also observed between mean sedentary bout length and the orientation domain (p for trend = 0.009). No significant associations were observed for global cognitive function or other cognitive domains. Sedentary time accumulated in prolonged bouts, but not total sedentary time, was inversely associated with orientation ability among older adults. Our results encourage further researches to confirm the role of prolonged sedentary time in changes to cognitive domains over time among older adults.

Levels and Correlates of Objectively Measured Sedentary Behavior in Young Children: SUNRISE Study Results from 19 Countries.

ABSTRACTPurposeThere is a paucity of global data on sedentary behavior during early childhood. The purpose of this study was to examine how device-measured sedentary behavior in young children differed across geographically, economically, and sociodemographically diverse populations, in an international sample.MethodsThis multinational, cross-sectional study included data from 1071 children 3–5 yr old from 19 countries, collected between 2018 and 2020 (pre-COVID). Sedentary behavior was measured for three consecutive days using activPAL accelerometers. Sedentary time, sedentary fragmentation, and seated transport duration were calculated. Linear mixed models were used to examine the differences in sedentary behavior variables between sex, country-level income groups, urban/rural settings, and population density.ResultsChildren spent 56% (7.4 h) of their waking time sedentary. The longest average bout duration was 81.1 ± 45.4 min, and an average of 61.1 ± 50.1 min·d−1 was spent in seated transport. Children from upper-middle–income and high-income countries spent a greater proportion of the day sedentary, accrued more sedentary bouts, had shorter breaks between sedentary bouts, and spent significantly more time in seated transport, compared with children from low-income and lower-middle–income countries. Sex and urban/rural residential setting were not associated with any outcomes. Higher population density was associated with several higher sedentary behavior measures.ConclusionsThese data advance our understanding of young children’s sedentary behavior patterns globally. Country income levels and population density appear to be stronger drivers of the observed differences, than sex or rural/urban residential setting.

Changes in sedentary behavior patterns during the transition from childhood to adolescence and their association with adiposity: a prospective study based on compositional data analysis

BackgroundTo date, no longitudinal study using a compositional approach has examined sedentary behavior (SB) patterns in relation to adiposity in the pediatric population. Therefore, our aims were to (1) investigate the changes in SB patterns and adiposity from childhood to adolescence, (2) analyze the prospective compositional associations between changes in SB patterns and adiposity, and (3) estimate the changes in adiposity associated with substituting SB with physical activity (PA) of different intensities.MethodsThe study presents a longitudinal design with a 5-year follow-up. A total of 88 participants (61% girls) were included in the analysis. PA and SB were monitored for seven consecutive days using a hip-worn accelerometer. Adiposity markers (fat mass percentage [FM%], fat mass index [FMI], and visceral adiposity tissue [VAT]) were assessed using the multi-frequency bioimpedance analysis. The prospective associations were examined using compositional data analysis.ResultsOver the follow-up period, the proportion of time spent in total SB increased by 154.8 min/day (p < 0.001). The increase in total SB was caused mainly by an increase in middle and long sedentary bouts, as these SB periods increased by 79.8 min/day and 62.0 min/day (p < 0.001 for both), respectively. FM%, FMI, and VAT increased by 2.4% points, 1.0 kg/m2, and 31.5 cm2 (p < 0.001 for all), respectively. Relative to the remaining movement behaviors, the increase in time spent in middle sedentary bouts was significantly associated with higher FM% (βilr1 = 0.27, 95% confidence interval [CI]: 0.02 to 0.53) at follow-up. Lower VAT by 3.3% (95% CI: 0.8 to 5.7), 3.8% (95% CI: 0.03 to 7.4), 3.9% (95% CI: 0.8 to 6.9), and 3.8% (95% CI: 0.7 to 6.9) was associated with substituting 15 min/week spent in total SB and in short, middle, and long sedentary bouts, respectively, with an equivalent amount of time spent in vigorous PA.ConclusionsThis study showed unfavorable changes in SB patterns and adiposity status in the transition from childhood to adolescence. Incorporating high-intensity PA at the expense of SB appears to be an appropriate approach to reduce the risk of excess adiposity in the pediatric population.

Measuring sedentary behavior using waist- and thigh-worn accelerometers and inclinometers - are the results comparable?

Background:Objective sensor-based quantification of sedentary behavior is an important tool for planning and evaluating interventions for excessive sedentary behavior in patients with musculoskeletal diseases. Although waist-worn accelerometers are the standard for physical activity (PA) assessment, only thigh-worn inclinometers can clearly distinguish sedentary behavior from any light PA or standing activity.Methods:In this study, 53 adults (ages 20–85 years) wore two ActiGraph wGT3X-BT monitors, each containing an inclinometer and accelerometer (set for acquisition of slow movements in all three planes), attached to the right waist and thigh for a period of about 4 days. Both monitors recorded total sedentary time and continuous sedentary 10-min bouts by synchronous accelerometry and inclinometry. Differences and correlations between methods and wearing positions were evaluated against participant age, body mass index (BMI), and number of steps taken. Thigh-worn inclinometry was used as reference.Results:Data from thigh-worn inclinometry and waist-worn accelerometry were highly correlated for total sedentary time [rho = 0.888; intraclass correlation coefficient (ICC) = 0.937] and time in sedentary bouts (rho = 0.818; ICC = 0.848). Nevertheless, accelerometry at the waist underestimated sedentary time by ≈17% (p < 0.001) and time in sedentary bouts by ≈54% (p < 0.001). A satisfactory concordance thus could be demonstrated only for total sedentary time, based on the Bland–Altmann method (≈96% of data within the limits of agreement). The differences between waist-worn accelerometry and thigh-worn inclinometry did not correlate with age but did correlate with BMI and PA for both sedentary behavior parameters (r ⩾ 0.240, p ⩽ 0.043).Conclusion:A waist-worn accelerometer can be used to determine total sedentary time under free-living conditions with sufficient accuracy if the correct settings are chosen. Further investigations are necessary to investigate why short sedentary bouts cannot be reliably assessed.Trial registration:DRKS00024060 (German Clinical Trials Register)

Association between patterns of sedentary time and academic performance in adolescents: the mediating role of self-concept.

Objective:To analyze the association between the pattern of sedentary time (bouts and breaks) with academic performance, with an emphasis on the mediating role of self-concept.Methods:Participants in the cross-sectional study were 394 adolescents (208 girls), aged 10–14 years, from sixth grade from Londrina, Paraná, Brazil. The sedentary time pattern was measured through accelerometry. Definitions: sedentary bouts — uninterrupted periods of sedentary behavior; breaks — non-sedentary period between two sedentary bouts. The self-concept was estimated using the Piers-Harris II Inventory. Academic performance was obtained by school grades.Results:Short sedentary bouts were associated with higher academic performance in boys (1–4 minutes: β=0.035, p=0.007) and girls (1–4 minutes: β=0.031, p=0.014; 5–14 minutes: β=0.054, p=0.001). Long bouts (30 minutes) were associated with lower academic performance in boys (β=-0.023; p=0.011) and girls (β=-0.032; p<0.001). For girls, total and intellectual self-concept mediated the association between all sedentary pattern and academic performance (bouts 1–4 minutes [total: 39% and intellectual: 42.8%]; bouts 5–14 minutes [total: 21.5% and intellectual: 35.4%]; bouts ≥30 minutes [total: 22.6% and intellectual: 32.3%]; and breaks [total: 38.9% and intellectual: 40.7%]). For boys, the total (56.4%) and intellectual (82.9%) self-concept mediated only the association between bouts of 5–14 minute and academic performance.Conclusions:The pattern of sedentary time is associated with academic performance in adolescents and this association is mediated by self-concept, especially in girls.

Ecological Validity of Prolonged Sitting Studies: How Well Do They Represent Real-Life Sedentary Patterns? A Pilot Study

ABSTRACT Acute prolonged sitting studies have been frequently implemented to determine the physiological effect of sedentary time on vascular and metabolic health. The length of these laboratory-based prolonged sitting studies ranges from 1.5 to 6 h, with most being 3 h in duration. Whether or not these sitting durations reflect true habitual prolonged sitting patterns is unclear. The purpose of this pilot study was to examine the habitual sedentary patterns of a heterogeneous sample to inform the design of future acute laboratory-based sitting studies. Participants (n = 121; 48 females) wore an activPAL inclinometer on their thigh 24 h·d−1 for 6.5 ± 0.7 d. A customized LabVIEW program determined daily averages of waking hours spent standing versus sitting and/or laying. The number of prolonged sedentary bouts (e.g., number of sedentary bouts &gt;30 min) and the frequency of sedentary breaks (per waking hour) were also calculated. Overall, participants engaged in 9.4 ± 1.9 h·d−1 of sedentary time. Participants frequently engaged in sedentary bouts between 0.5 and 1.0 h (3.5 ± 1.1 bouts per day) and between 1 and 2 h (1.7 ± 0.8 bouts per day) in duration. By contrast, they rarely engaged in bouts &gt;2 h without interruption (i.e., once every ~5 d). Very few participants engaged in any prolonged sedentary bouts between 3 and 4 h (n = 25; 21%) or &gt;4 h (n = 6, 5%). Participants averaged 2.9 ± 0.7 sedentary breaks per hour (i.e., every ~21 min), with the majority (n = 83, 69%) breaking up their sitting time every 17–30 min (i.e., 2–3.5 breaks per hour). To maximize the ecological validity, our preliminary findings indicate that acute models of prolonged sitting should be 1–2 h in length and strategies to break up prolonged sitting implemented every 20–30 min. The results from this pilot study may be used to inform large epidemiological studies to characterize prolonged sitting patterns in a variety of populations to assist in translating findings from the laboratory to the habitual setting.

Does physical activity moderate the association between device-measured sedentary time patterns and depressive symptoms in adults?

To investigate the association between sedentary time (ST) patterns and depressive symptoms, and whether moderate-to-vigorous physical activity (MVPA) can moderate this association. This cross-sectional study included a representative sample of 243 adults (mean age 41.8±16.7 years, 56.4% women) from a city in Southeast Brazil. Depressive symptoms were estimated through the Hospital Anxiety and Depression Scale (HADS). ST patterns (i.e., number of breaks, mean length of sedentary bouts, and number of long sedentary bouts), total ST, and MVPA were assessed using accelerometers. Poisson regression models revealed associations of total ST (ß = 0.063; 95%CI 0.011 to 0.116) and number of long bouts (0.108; 0.047 to 0.171) with depressive symptoms among men. MVPA moderated the associations of breaks and longer bouts of ST with depressive symptoms, with an increase of one break/hour, the increase of one long bout, and a decrease of 1 minute in mean bout length being associated with a reduction of 0.211 and increases of 0.081 and 0.166, respectively, in the number of depressive symptoms among men with physical inactivity (breaks = -0.211; -0.360 to -0.063; mean bout length = 0.081; 0.003 to 0.158; number of long bouts = 0.166; 0.090 to 0.242). Interventions that encourage breaking up ST should be helpful to reduce depressive symptoms among people with physical inactivity.

Association of Sedentary and Active Bout Frequency With Mortality in Older Men Using Accelerometry

BACKGROUND: Time spent sedentary increases with age and has several negative health consequences. We sought to examine associations between daily sedentary and active bout frequency with all-cause mortality. METHODS: Data are from 2,918 men in the Osteoporotic Fractures in Men (MrOS) study (mean age at Visit 3±SD: 79.0±5.1 years) with valid activity monitor data (5.1±0.3 days worn>90%) at Year 7 visit (Visit 3, 2007-2009). Sedentary and active bout frequencies are defined as the daily transition frequency from a sedentary bout lasting 5+ minutes to activity of any intensity, and the transition frequency from an active bout lasting 5+ minutes to sedentary. Deaths were centrally adjudicated using death certificates. Cox proportional hazard models were used to examine associations between quartiles of sedentary (Q1 referent, <13.6 bouts/day) or active (Q1 referent, <5 bouts/day) bout frequency and mortality. Models were repeated, stratifying by median daily total time spent sedentary and active. RESULTS: After 9.4±3.7 years of follow-up, 1,487 (51.0%) men died. Men averaged 16.9±5.1 and 8.2±4.2 sedentary and active bouts/day, respectively. After full covariate adjustment, each quartile reflecting a higher sedentary (Q4 vs Q1 HR: 0.68, 95%CI: 0.58-0.81, p-trend<0.001) and active bout (Q4 vs Q1 HR: 0.57, 95%CI: 0.48-0.68, p-trend<0.001) frequency was associated with lower mortality risk. There was no evidence that effects differed by total sedentary time (p-interaction for sedentary bout frequency and total sedentary time>0.05). CONCLUSIONS: More frequent, prolonged sedentary and active bouts are associated with a lower mortality risk in older men and is not moderated by total sedentary time.

Objectively Measured Physical Activity, Sedentary Behavior, and Incident Fracture in Older Women: The OPACH Study

Women aged 65 and older experience nearly three-fourths of the 2 million osteoporotic fractures annually in the US, yet whether accelerometer-measured volumes and intensities of physical activity and sedentary behavior (SB) are associated with reduced fracture risk is understudied. We investigated associations of accelerometer-measured light physical activity (LPA), moderate-to-vigorous physical activity (MVPA), sedentary time (ST), and mean sedentary bout duration (MBD) with incident clinical fractures (hip, vertebral, pelvis, lower leg, upper arm, forearm, and wrist) in the WHI OPACH cohort. Participants (N=6248; mean±SD age=78.6±6.7; 34% Black, 17% Hispanic) without prior hip fracture wore the ActiGraph GT3X+ for 7 days between May 2012-April 2014 and were followed through March 2020 for incident clinical fracture (N=711). Cox models estimated hazard ratios (HR) and 95% confidence intervals (CI), adjusting for age, race-ethnicity, education, alcohol, smoking, height, weight, falls history, RAND-36 physical function, diabetes, thiazide use, prescription osteoporotic therapy, and age at menopause. The HR(95% CI) across MVPA quartiles was 1.00(reference), 1.15(0.93-1.41), 0.90(0.72-1.13), and 0.79(0.61-1.02); p-trend=0.01. The HR(95% CI) for a one-interquartile range increment in MVPA (42 minutes/day) was 0.86(0.76-0.97). Associations were modified by prescription osteoporotic therapy [no: HR=0.77(0.66-0.89), yes: HR=1.03(0.85-1.25); p-interaction=0.01] and varied in magnitude by age[<80: HR=0.78(0.64-0.96), ≥80: HR=0.92(0.79-1.07); p-interaction=0.09], BMI [<30 kg/m2: HR=0.85(0.75-0.97), ≥30 kg/m2: HR=0.90(0.67-1.19); p-interaction=0.08], and race-ethnicity [Black: HR =0.63(0.44-0.89), Hispanic: HR =0.78(0.56-1.09), White: HR =0.92(0.80-1.06); p-interaction=0.16]. LPA, ST, or MBD were not associated with incident fractures. These data suggest that MVPA may reduce and not increase fracture risk and that LPA and SB do not increase fracture risk.

A new measure to quantify sedentary behavior using accelerometer data: Application to the Hispanic Community Health Study/Study of Latinos.

Availability of accelerometer data has made it possible to objectively and continuously monitor sedentary behavior. Various summaries of the extensive accelerometer data have been used to understand the relationship between sedentary behavior and health. However, the widely used summary measures on sedentary bouts, average bout length or its derivatives, fail to reveal patterns of accumulated sedentary behavior over time. Studies have suggested that prolonged uninterrupted sedentary behavior can be an important metric that is related to health states. Yet existing measures to capture the prolonged sedentary patterns either rely on parametric assumptions on the underlying distribution of sedentary bout length or have to categorize sedentary bout length into somewhat arbitrary categories. Gini index was also used; however, it only measures the variability in bout lengths but not the actual length. To overcome these limitations, we proposed a non-parametric weighted survival function to characterize uninterrupted sedentary behavior over time in a continuous fashion and used the area under the survival curve as a new summary measure to quantify sedentary behavior. We showed that this measure is a weighted average of bout length and contains the information on both the mean and variability of bout lengths. We demonstrated in the simulation studies that the proposed measure could better identify prolonged uninterrupted sedentary behavior and predict health outcomes. We applied this new measure and existing sedentary measures to data from the Hispanic Community Health Study/Study of Latinos to examine the association between sedentary behavior and overweight/obesity.

Objectively Measured Physical Activity and Sedentary Time Among Adults With and Without Stroke: A National Cohort Study.

We examined differences in the volume and pattern of physical activity (PA) and sedentary behavior between adults with and without stroke. We studied cohort members with an adjudicated or self-reported stroke (n=401) and age-, sex-, race-, region of residence-, and body mass index-matched participants without a history of stroke (n=1203) from the REGARDS study (Reasons for Geographic and Racial Differences in Stroke). Sedentary behavior (total volume and bouts), light-intensity PA, and moderate-to-vigorous-intensity PA were objectively measured for 7 days via hip-worn accelerometer. Sedentary time (790.5±80.4 versus 752.4±81.9 min/d) and mean sedentary bout duration (15.7±12.6 versus 11.9±8.1 min/d) were higher and PA (light-intensity PA: 160.5±74.6 versus 192.9±73.5 min/d and moderate-to-vigorous-intensity PA: 9.0±11.9 versus 14.7±17.0 min/d) lower for stroke survivors compared with controls (P<0.001). Stroke survivors also accrued fewer activity breaks (65.5±21.9 versus 73.31±18.9 breaks/d) that were shorter (2.4±0.7 versus 2.7±0.8 minutes) and lower in intensity (188.4±60.8 versus 217.9±72.2 counts per minute) than controls (P<0.001). Stroke survivors accrued a lower volume of PA, higher volume of sedentary time, and exhibited accrual patterns of more prolonged sedentary bouts and shorter, lower intensity activity breaks compared with persons without stroke.

Objectively Measured Patterns of Daily Physical Activity and Phenotypic Frailty.

Self-reported low physical activity is a defining feature of phenotypic frailty but does not adequately capture physical activity performed throughout the day. This study examined associations between accelerometer-derived patterns of routine daily physical activity and frailty. Wrist accelerometer and frailty data from 638 participants (mean age 77 [SD = 5.5] years; 44% women) were used to derive 5 physical activity metrics: active minutes/day, sedentary minutes/day, total activity counts/day, activity fragmentation (reciprocal of the average active bout length), and sedentary fragmentation (reciprocal of the average sedentary bout length). Robust, prefrail, and frail statuses were identified using the physical frailty phenotype defined as having 0, 1-2, or ≥3 of the following criterion: weight loss, exhaustion, slowness, self-reported low activity, and weakness. Frailty was collapsed into not frail (robust and prefrail) and frail, and each frailty criteria was dichotomized. Multiple logistic regression was used to model each accelerometer metric. Separate frailty criteria and interactions with age and sex were also examined. With higher amounts and intensity of daily activity (more active minutes, fewer sedentary minutes, higher activity counts) and lower activity fragmentation, the odds of frailty were lower compared to robust/prefrail states (p < .02 for all). For interactions, only an age by sedentary fragmentation interaction on the odds of frailty was observed (p = .01). For each separate criteria, accelerometer metrics were associated with odds of slowness, low activity, and weakness. Less favorable patterns of objectively measured daily physical activity are associated with frailty and the components of slowness, low self-reported activity, and weakness.

Bidirectional associations between sedentary time and sleep duration among 12- to 14-year-old adolescents

BackgroundThe aim of this study was to investigate bidirectional associations between (prolonged) sitting time and sleep duration in 12- to 14-year-old adolescents using a between-subjects and within-subjects analyses approach.MethodsObservational data were used from 108 adolescents (53% girls; mean age 12.9 (SD 0.7) years) from six schools in Flanders, Belgium. The Axivity AX3 triaxial accelerometer, worn on the thigh, was used to assess daily total sitting time and daily time spent in sedentary bouts of ≥30 min (as a proxy for prolonged sitting time). The Fitbit Charge 3 was used to assess nightly sleep duration. Both monitors were worn on schooldays only (ranging from 4 to 5 days). Linear mixed models were conducted to analyse the associations, resulting in four models. In each model, the independent variable (sleep duration, sitting time or prolonged sitting time) was included as within- as well as between-subjects factor.ResultsWithin-subjects analyses showed that when the adolescents sat more and when the adolescents spent more time sitting in bouts of ≥30 min than they usually did on a given day, they slept less during the following night (p = 0.01 and p = 0.05 (borderline significant), respectively). These associations were not significant in the other direction. Between-subjects analyses showed that adolescents who slept more on average, spent less time sitting (p = 0.006) and less time sitting in bouts of ≥30 min (p = 0.004) compared with adolescents who slept less on average. Conversely, adolescents who spent more time sitting on average and adolescents who spent more time sitting in bouts of ≥30 min on average, slept less (p = 0.02 and p = 0.003, respectively).ConclusionsBased on the between-subjects analyses, interventions focusing on reducing or regularly breaking up sitting time could improve adolescents’ sleep duration on a population level, and vice versa. However, the within-subjects association was only found in one direction and suggests that to sleep sufficiently during the night, adolescents might limit and regularly break up their sitting time the preceding day.Trial registrationData have been used from our trial registered at ClinicalTrials.gov (NCT04327414; registered on March 11, 2020).