Isotemporal Substitution Models Research Articles

The Cross-Sectional and Longitudinal Association Between 24-Hour Movement Behavior Compositions With Body Mass Index, Waist Circumference, and Internalizing and Externalizing Symptoms in 6-Year-Old Children.

Few studies have examined the association between 24-hour movement behaviors and health in children in their first 2years of primary school. This study aimed to examine how 24-hour movement behavior compositions at age 6 were related to body mass index (BMI), waist circumference, and internalizing and externalizing symptoms at ages 6 and 10. A subsample of 361 children from the HealthNuts cohort study with valid accelerometer data was included in the cross-sectional analysis. Of these, 279 had longitudinal data for social-emotional outcomes and 113 had longitudinal anthropometric data. Children's 24-hour movement behaviors (ie,sleep, sedentary time, light-intensity physical activity, and moderate- to vigorous-intensity physical activity [MVPA]) were assessed over 8days using accelerometery and activity logs. BMI z score and waist circumference were assessed using standardized protocols, and parents reported on their child's internalizing and externalizing behaviors. Cross-sectional and longitudinal associations were estimated using compositional data analysis and compositional isotemporal substitution analysis. Overall, 24-hour movement behaviors were significantly related to internalizing symptoms cross-sectionally and longitudinally and BMI z-score cross-sectionally. Results from compositional isotemporal substitution models indicated that replacing sedentary time or light-intensity physical activity with MVPA was associated with fewer internalizing symptoms at ages 6 and 10. Replacing time spent sedentary and in light-intensity physical activity or MVPA with sleep was associated with lower BMI z score at age 6. Spending more time in MVPA relative to other movement behaviors is associated with fewer internalizing symptoms. In additional, spending more time sleeping is associated with lower BMI z score and waist circumference in children.

Cross-sectional associations between sedentary time with cognitive engagement and brain volume among community-dwelling vulnerable older adults.

Vulnerable older adults tend to decrease physical activity (PA) and increase sedentary time (ST). Previous research on the associations between ST and brain volume have yielded inconsistent findings, without considering the impact of cognitive engagement (CE) on cognitive function. We aimed to examine the association between ST with CE and brain volume. A structural magnetic resonance imaging survey was conducted among community-dwelling vulnerable older adults. Brain volumetric measurements were obtained using 3T magnetic resonance imaging and pre-processed using FreeSurfer. ST with low or high CE was assessed using a 12-item questionnaire. PA was assessed by the frequency of light and moderate levels of physical exercise according to the Japanese version of the Cardiovascular Health Study criteria. Participants were categorized into a low PA group and a moderate-to-high PA group. Among 91 participants (83.1 ± 5.2 years old, 61.5% female), 26 were low PA. The overall sample and moderate-to-high PA group did not show significant positive associations with brain volume for ST with high CE. In the low PA group, isotemporal substitution models showed that replacing ST with low CE by ST with high CE was significantly associated with increased brain volume in some areas, including the rostral and caudal anterior cingulate (β = 0.486-0.618, all P < 0.05, adjusted R2 = 0.344-0.663). Our findings suggest that replacing ST with low CE by ST with high CE is positively associated with brain volume in vulnerable older adults with low PA. Geriatr Gerontol Int 2024; 24: 82-89.

SEDENTARY BEHAVIOR DIFFERENTIALLY INFLUENCES COGNITIVE HEALTH IN OLDER ADULTS AT DIFFERENT TIMESCALES

Abstract The negative health effects of sedentary behavior have received increased attention over the past decade. Whether sedentary behavior negatively influences cognitive health at any timescale remains poorly understood. Our study sought to determine whether sedentary behavior negatively affects cognitive health throughout the adult lifespan at multiple timescales (acute within-day, day-to-day, cross-sectionally). We examined ambulatory assessment data generated by an adult lifespan sample (N=161; age range:19-88 years; 84% F) where cognition was repeatedly assessed via ultra-brief cognitive assessments of processing speed and working memory in an ecological momentary assessment (EMA) framework (6 assessments/day for 14 days). Activity was measured continuously via thigh-worn ActivPAL monitors. ActivPAL and EMA data were combined and modeled in a multi-level (3-level; moments within days within persons) isotemporal substitution modeling framework. Increased sedentary behavior was associated with acute decreases in processing speed for older participants (65+ years of age) and substitution modeling indicated that exchanging bouts of walking or standing for sedentary time would result in short-term improvements. In contrast, a consistent result across younger and older adults indicated that days with generally more sedentary time (as well as lying and standing) were associated with overall better processing speed and working memory capacity. No cross-sectional associations were observed. A lack of cross-sectional associations between sedentary behavior and cognitive performance was consistent with previous studies. Our current results extend previous findings by showing that sedentary behavior might influence cognitive performance differently at different timescales in younger and older adults.

Reallocating desk workers' sitting time to standing or stepping: associations with work performance.

Studies have suggested that sitting time at work may lead to underperformance but they may underestimate the benefits to desk workers' performance of reducing occupational sitting time without considering the relative effects of the specific activities replaced. To estimate differences in work performance (presenteeism, absenteeism and engagement) when occupational sitting time is reallocated to standing/stepping in desk workers. Data for middle-aged desk workers were from a Japan-wide online survey (n = 2228). Self-report proportion of occupational sitting and standing/stepping, work hours and work performance indicators, including absolute (ratings relating only to self) and relative (ratings of self, compared to others) presenteeism and absenteeism, and dimensions of work engagement, were collected. Partition and isotemporal substitution models were used to investigate the associations of occupational sitting and standing/stepping time with work performance, including their reallocation effects. In partition models, longer occupational sitting time was associated with a lower absolute presenteeism score (i.e. less productivity), lower absolute absenteeism (i.e. longer-than-expected work hours), and lower engagement. Longer occupational standing/stepping time was associated with lower absolute absenteeism and more engagement. Isotemporal substitution models showed that each hour of occupational sitting reallocated to standing/stepping was favourably associated with overall work engagement (B = 0.087; 95% confidence interval 0.051, 0.122) and its dimensions (B ranged from 0.078 to 0.092), but was not associated with presenteeism or absenteeism. These findings suggest that management support and practical initiatives to encourage desk workers to replace portions of their sitting time with standing/stepping may contribute to enhanced work engagement.

Associations of sleeping patterns and isotemporal substitution of other behavior with the prevalence of CKD in Chinese adults.

Studies have found a U-shaped relationship between sleep duration and chronic kidney disease (CKD) risk, but limited research evaluated the association of reallocating excessive sleep to other behavior with CKD. We included 104 538 participants from the nationwide cohort of the Risk Evaluation of Cancers in Chinese Diabetic Individuals: A Longitudinal Study, with self-reported time of daily-life behavior. Using isotemporal substitution models, we found that substituting 1 h of sleeping with sitting, walking, or moderate-to-vigorous physical activity was associated with a lower CKD prevalence. Leisure-time physical activity displacement was associated with a greater prevalence reduction than occupational physical activity in working population. In stratified analysis, a lower CKD prevalence related to substitution toward physical activity was found in long sleepers. More pronounced correlations were observed in long sleepers with diabetes than in those with prediabetes, and they benefited from other behavior substitutions toward a more active way. The U-shaped association between sleep duration and CKD prevalence implied the potential effects of insufficient and excessive sleep on the kidneys, in which the pernicious link with oversleep could be reversed by time reallocation to physical activity. The divergence in the predicted effect on CKD following time reallocation to behavior of different domains and intensities and in subpopulations with diverse metabolic statuses underlined the importance of optimizing sleeping patterns and adjusting integral behavioral composition.

Replacing screen time, with physical activity and sleep time: influence on cardiovascular indicators and inflammatory markers in Brazilian children

ObjectiveTo examine if the substitution of different screen time intervals with light physical activity (LPA), moderate to vigorous physical activity (MVPA) and sleep is associated with cardiovascular indicators and inflammatory markers in children. MethodsThis is a cross-sectional study developed with 186 children aged between six and 11 years old from public schools in southern Brazil. CRF was measured with the 6-minute running and walking test, following the Brazil Sports Project procedures. The percentage of fat was evaluated through DXA. LPA and MVPA were measured using accelerometers. Sleep and screen time were assessed by questionnaires answered by parents. Leptin and C-reactive protein were measured by fasting blood collection. Systolic and diastolic blood pressure were determined through a digital sphygmomanometer. Isotemporal substitution models were used for statistical analysis. ResultsReplacing 1 h of screen time with MVPA was associated with lower BMI, systolic and diastolic blood pressure, fat percentage, leptin, and C-reactive protein. When screen time was substituted for sleep time, lower waist circumference was observed. Regarding the substitution of 1 h of screen time with LPA, significant values were found only for leptin. ConclusionThe replacement of screen time with physical activities of different intensities and sleep time was associated with benefits in cardiovascular indicators and inflammatory markers in childhood.

Correlation analysis between physical activity and depressive tendencies among occupational groups: an isotemporal substitution approach

ObjectivesSedentary behaviour (SB) and physical activity (PA) have been shown to be associated with depression. However, behaviours, such as PA, occupy a portion of an individual’s 24-h day. Thus, an increase in time for one behaviour takes away time from another. Previous evidence suggests that it would be more appropriate to shift the focus to the importance of reallocating time spent in sedentary behaviour to time spent in physical activity. The aim of this study was to analyse the mutual replacement effect of different health behaviours on depressive tendencies by isotemporal substitution modelling (ISM) under the objective condition of considering a limited 24-h day. Second, we aimed to further explore the potential association between excessive or insufficient sleep duration and depressive symptoms.MethodsA total of 10656 employees from 79 companies in four provinces of China participated in this survey.The Center for Epidemiological Studies Depression Scale (CES-D) was used to measure workers’ depressive tendencies. The duration of various types of physical activity was self-reported by workers based on the International Physical Activity Questionnaire (IPAQ). ISM was used to assess the associations of time spent in different activities on displacement of equivalent time spent on other activities with depression risk.ResultsA total of 10656 participants (89.5% of the sample) were included in the analysis.The ISM found that a 30-min unit of SB replaced with walking (OR, 95% CI: 0.83, 0.77–0.88), sleep (≤ 8 h) (OR, 95% CI: 0.77, 0.74–0.79), moderate physical activity (MPA) (OR, 95% CI: 0.87, 0.81–0.93) and vigorous physical activity (VPA) (OR, 95% CI: 0.91, 0.84–0.99) was significantly and negatively associated with the risk of depressive tendencies. When sleep duration was less than 8 h, each additional half hour of sleep time was significantly associated with a lower risk of depressive tendencies, and this association was no longer significant after 8 h.ConclusionProlonged SB is common in the current workplace in China. Replacing an average of 30 min per day of SB with VPA and MPA, even walking is associated with less depression among workers. In addition, insufficient daily sleep is also an important risk factor for workers' depressive tendencies. These findings provide valuable evidence to promote mental health among occupational groups and support the development of healthy workplaces.

Association between depression, anemia and physical activity using isotemporal substitution analysis.

Depression is a leading cause of disability and mortality, with estimated number of deaths exceeding 2.2million worldwide. We examined depression in relation to anemia and physical activity, both of which have an impact on depression mechanisms. This cross-sectional study used data from the Korean National Health and Nutrition Examination Survey, including 18,622 participants. Depression was measured by The Patient Health Questionnaire-9, and physical activity was assessed by the Global Physical Activity Questionnaire. Anemia was defined by World Health Organization criteria for blood hemoglobin levels. Isotemporal substitution model for physical activity was used to assess the effect of replacing sedentary behavior to each intensity level of physical activity. Logistic regression was applied to estimate the association on depression. Replacing sedentary behavior with moderate or vigorous physical activity was associated with a lower risk of depression in the anemic (OR: 0.875, 95% CI: 0.782-0.978) and non-anemic groups (OR: 0.943, 95% CI: 0.919-0.967). Depression risk was significantly reduced by replacing walking with moderate to vigorous physical activity in both anemic (OR: 0.877, 95% CI: 0.784-0.982) and non-anemic groups (OR: 0.951, 95% CI: 0.927-0.976). Moderate to vigorous physical activity had a protective association against depression in both anemic and non-anemic groups. Anemic patients are recommended to perform physical activity for any duration acceptable to them to prevent depression.

Accelerometer-Measured Sedentary Behavior Patterns, Brain Structure, and Cognitive Function in Dementia-Free Older Adults: A Population-Based Study.

Sedentary behavior is associated with cognitive impairment, but the neuropathological mechanisms underlying their associations are poorly understood. To investigate the associations of accelerometer-measured sedentary behavior patterns with brain structure and cognition, and further to explore the potential mechanisms. This community-based study included 2,019 older adults (age≥60 years, 59% women) without dementia derived from participants in the baseline examination of MIND-China (2018-2020). We assessed sedentary parameters using an accelerometer and cognitive function using a neuropsychological test battery. Structural brain markers were assessed on the structural brain MRI scans in a subsample (n = 1,009). Data were analyzed using the general linear, isotemporal substitution, and mediation models. In the total sample (n = 2,019), adjusting for multiple covariates and moderate-to-vigorous-intensity physical activity, longer mean sedentary bout duration was linearly related with lower z-scores of global cognition, verbal fluency, and memory (ptrend < 0.05), whereas greater total sedentary time was linearly associated with lower z-scores of global cognition, verbal fluency, and memory only among individuals with long sedentary time (>10 h/day) (ptrend < 0.05); Breaking up sedentary time with same amount of light-intensity physical activity was significantly associated with higher verbal fluency and memory z-scores (p < 0.05). In the MRI subsample (n = 1,009), separately entering structural brain MRI markers into the mediation models substantially attenuated the associations of mean sedentary bout duration with global cognition, verbal fluency, and memory z-scores. Prolonged uninterrupted sedentary time is associated with poor global cognition, memory, and verbal fluency among rural older adults, and structural brain markers could partially mediate the association.

Replacement of watching television with physical activity and the change in gestational diabetes mellitus risk: A case-control study.

To evaluate the effect of replacing 1 h/week of watching television with 1 h/week of light to moderate (LMPA) or vigorous physical activity (VPA) before and during pregnancy on the risk of gestational diabetes mellitus (GDM). A case-control study was conducted in pregnant women. Physical activity and television watching before and during pregnancy were assessed using the Paffenbarger Physical Activity Questionnaire. Each type of activity was classified according to intensity (metabolic equivalent of task; MET): less than 6 METs is LMPA, 6 METs or more is VPA. The duration of physical activity and watching television was calculated, and logistic regression models were used to estimate adjusted odds ratios (aOR) and 95% confidence intervals for their association with GDM risk. The isotemporal substitution model was used to calculate the effect of replacing 1 h/week of watching television with the same duration of physical activity. The GDM cases (n = 290) spent less time performing VPA than controls without GDM (n = 1175) and more time watching television during pregnancy (P < 0.05). During pregnancy, the risk of GDM increased for each hour of watching television (aOR = 1.02; 95% confidence interval 1.00-1.03). Women who spent more time watching television during pregnancy were likely to develop GDM (aOR>14 h/week vs. 0-6 h/week = 2.03; 95% confidence interval 1.35-3.08). Replacing 1 h/week of watching television with 1 h/week of VPA during pregnancy could decrease the chance of developing GDM (aOR = 0.66; 95% confidence interval 0.43-1.00). A simple change of 1 h/week of watching television for 1 h/week of VPA in pregnant women may reduce the risk of GDM considerably.

Optimal domain-specific physical activity and sedentary behaviors for blood lipids among Japanese children: a compositional data analysis

BackgroundOptimizing childhood domain-specific physical activity (PA) and sedentary behavior (SB) for blood lipid profile is not well understood. We aimed to (1) determine the associations between accelerometer-measured PA and SB for each domain (school time and out-of-school time) with blood lipid profile and (2) estimate predicted changes in blood lipid profile with hypothetical time-reallocation between domain-specific SB and PA among Japanese children using compositional data analysis (CoDA).MethodsThis cross-sectional study included 284 children (147 boys and 137 girls) aged 9–12 years (mean age [years]: 10.1 ± 1.2 for boys, 10.0 ± 1.1 for girls; mean body mass index: 18.2 ± 3.2 for boys, 17.5 ± 2.5 for girls). Time spent in domain-specific SB, light-intensity PA (LPA), moderate-intensity PA (MPA), and vigorous-intensity PA (VPA) was assessed using accelerometry. The non-fasting lipid profile considered measures of triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and non-HDL-C levels. CoDA and isotemporal substitution model were performed to examine the associations of domain-specific PA and SB with blood lipids.ResultsTime spent in out-of-school VPA relative to the other behaviors was negatively associated with non-HDL-C (boys: βilr1 = − 0.10, 95% confidence interval [CI] = − 0.19 to − 0.01), TG (boys: βilr1 = − 0.45, 95% CI = − 0.68 to − 0.22), and positively associated with HDL-C (girls: βilr1 = 0.09, 95% CI = 0.02 to 0.16) after adjusting for age, body mass index, and time spent in SB, LPA, and MPA. During the out-of-school period, a replacement of 1 min of any other behavior with VPA was associated with decreases in LDL-C in boys (predicted changes [95% CI] − 0.03 mmol/L [− 0.05 to − 0.00] for LPA), non-HDL-C in boys (predicted changes [95% CI] − 0.03 mmol/L [− 0.06 to − 0.01] for SB and LPA) and TG in boys (predicted changes [95% CI] − 0.04 mmol/L [− 0.06 to − 0.02] for SB and LPA, − 0.05 mmol/L [− 0.07 to − 0.02] for MPA) and in girls (predicted changes [95% CI] − 0.02 mmol/L [− 0.04 to − 0.00] for LPA), and increases in HDL-C in girls (predicted changes [95% CI] 0.02 mmol/L [0.00 to 0.04] for SB and LPA, 0.03 mmol/L [0.00 to 0.05] for MPA).ConclusionsIncreasing out-of-school VPA might be an effective approach to improve blood lipid profiles among Japanese children.

O.3.2-2 Substituting device-measured sedentary time with alternative 24-hour movement behaviours: compositional associations with adiposity, cardiometabolic risk and arterial stiffness in the ORISCAV-LUX 2 study

Abstract Purpose There is a considerable burden of sedentary time in European adults. We aimed to quantify the differences in adiposity, cardiometabolic risk biomarkers, and arterial stiffness associated with exchanging sedentary time for alternative 24-hour movement behaviours. Methods This observational cross-sectional study included Luxembourg residents aged 18-79y who each provided ≥4 valid days of triaxial accelerometry (n=1046). Covariable adjusted compositional isotemporal substitution models were used to examine if replacing device-measured sedentary time with more time in the sleep period, light physical activity (PA), or moderate-to-vigorous PA (MVPA) was associated with waist circumference, numerous biomarkers of cardiometabolic health (fasting plasma glucose and insulin, triglycerides, high-density lipoprotein cholesterol (HDL-c), the ratio of apolipoprotein B/A1), and arterial stiffness (carotid-femoral pulse wave velocity (cfPWV)). We further investigated the cardiometabolic properties of replacing sedentary time accumulated in prolonged (≥30 minute) with non-prolonged (&amp;lt;30 minute) bouts. The results are presented as 30 minute time exchanges (β (95% confidence interval)). Results Replacing 30 minutes of sedentary time with MVPA was favourably associated with waist circumference (-1.09 (-1.68 to -0.51) cm), HDL-c (1.30 (0.68 to 1.93) mg/dL), fasting glucose (-1.02 (-1.64 to -0.39) mg/dL), insulin (-4.71 (-7.12 to -2.24) %), and cfPWV (-1.70 (-2.76 to -0.62) %). Substituting sedentary time with light PA was associated with fasting insulin (-3.29 (-5.71 to -0.81) %), and was the only time-exchange to predict lower triglycerides (-2.32 (-4.38 to -0.21) %) and a lower apolipoprotein B/A1 ratio (-0.01 (-0.02 to -0.00)). Exchanging sedentary time with more time in the sleep period was associated with lower fasting insulin (-2.56 (-3.99 to -1.11)), and also with lower waist circumference (-1.39 (-2.30 to -0.48) cm) and cfPWV (-1.96 (-3.74 to -0.15) %) in short sleepers (&amp;lt;7h per night (n=349)). There was no evidence that replacing prolonged with non-prolonged sedentary time was related to outcomes. Conclusions Replacing sedentary time with MVPA is beneficially associated with the widest range of cardiometabolic risk factors, but light PA confers additional and unique benefit. Extending sleep, by redistributing sedentary time, may be an appropriate strategy to lower obesity risk and improve arterial health in short-sleeping individuals. Funding Luxembourg Institute of Health.

Accelerometer-measured physical activity patterns are associated with phenotypic age: Isotemporal substitution effects

Prolonged sitting appears to accelerate aging, while optimal physical activity patterns have been found to delay the process. It is an emerging topic, and no conclusions have been reached regarding the relationship between physical activity patterns and biomarkers-measured aging. Hence, the aim of this study was to investigate the association between sensor-based objectively measured physical activity and phenotypic age using a nationwide population from the National Health and Nutrition Examination Survey (NHANES) in the United States. Weighted linear regression models were performed to evaluate the association between sedentary behavior, light-intensity physical activity (LPA), moderate-to-vigorous physical activity (MVPA) and phenotypic age. A total of 6439 eligible participants were included and the weighted respondents were 49,964,300. Results showed that prolonged sitting was positively associated with phenotypic age in the fully adjusted model [β (95% CI): 0.009(0.007,0.011), p < 0.001], while increasing volume of LPA and MVPA was associated with younger phenotypic age using the fully adjusted model [β (95% CI): −0.010(-0.013,-0.006), p < 0.001; −0.062(-0.075,-0.048), p < 0.001]. By utilizing the Isotemporal Substitution Model, it was found that replacing 30 min of sedentary behavior with 30 min of LPA or MVPA per day was associated with estimated 0.4 or 1.9 years of phenotypic age reduction. According to the study's findings, maintaining a certain level of physical activity could delay the process of aging and intensity matters.

Replacing of sedentary behavior with physical activity and the risk of mortality in people with prediabetes and diabetes: a prospective cohort study

BackgroundSedentary behavior is prevalent among people with diabetes and is associated with unfavorable cardiometabolic health. However, there is limited evidence regarding the impact of replacing sedentary time (ST) with physical activity on mortality in people with prediabetes and diabetes. We prospectively examined the association between accelerometer-measured ST and mortality among people with prediabetes and diabetes after adjusting for demographic characteristics, lifestyle factors, and moderate- to vigorous-intensity PA (MVPA). We further determined the effect of replacing ST with equal time of different types of physical activities on all-cause mortality.MethodsWe included 1242 adults with prediabetes and 1037 with diabetes from the National Health and Nutrition Examination Survey. Restricted cubic splines were fitted to determine the dose–response association between ST and overall mortality. Isotemporal substitution modeling was used to explore the hazard ratio (HR) effects of ST replacement.ResultsDuring a median follow-up of 14.1 years, 424 adults with prediabetes and 493 with diabetes died. Compared with the lowest tertile of ST, the multivariable-adjusted HRs for all-cause mortality in the highest tertile were 1.76 (95% confidence interval [CI] 1.19, 2.60) for participants with prediabetes and 1.76 (1.17, 2.65) for those with diabetes. Additionally, a linear association between ST and all-cause mortality was observed in adults with prediabetes and diabetes, with HRs for each 60 min/day increment in ST of 1.19 (1.10, 1.30) and 1.25 (1.12, 1.40), respectively. Isotemporal substitution results indicated that individuals with prediabetes whose ST was replaced by 30 min of light-intensity physical activity (LPA) and MVPA had 9% and 40% lower all-cause mortality, respectively. In people with diabetes, replacing sedentary behavior with an equivalent time of LPA and MVPA was also associated with mortality risk reduction (HR 0.89; 95% CI 0.84, 0.95 for LPA; HR 0.73; 95% CI 0.49, 1.11 for MVPA).ConclusionsHigher ST was associated in a dose–response manner with an increased risk of premature mortality among adults with prediabetes and diabetes. Statistically replacing ST with LPA was potentially beneficial for health in this high-risk population.

Arterial stiffness and the reallocation of time between device-measured 24-hour movement behaviours: A compositional data analysis

Background and aimsArterial stiffness predicts cardiovascular morbidity and mortality. We aimed to quantify the differences in arterial stiffness associated with reallocating time between 24-h movement behaviours. MethodsThis observational cross-sectional study included Luxembourg residents aged 25-79y who each provided ≥4 valid days of triaxial accelerometry (n = 1001). Covariable adjusted compositional isotemporal substitution models were used to examine if theoretical reallocations of time between device-measured sedentariness, the sleep period, light physical activity (PA), and moderate-to-vigorous PA (MVPA) were associated with the percentage difference in carotid-femoral pulse wave velocity (cfPWV). We further investigated if replacing sedentary time accumulated in prolonged (≥30 min) with non-prolonged (<30 min) bouts was associated with arterial stiffness. The results are presented as 30 min time exchanges (β (95% confidence interval)). ResultsBeneficial associations with lower cfPWV were observed when reallocating time to MVPA from the sleep period (−1.38 (−2.63 to −0.12) %), sedentary time (−1.70 (−2.76 to −0.62) %), and light PA (−2.51 (−4.55 to −0.43) %), respectively. Larger associations in the opposite direction were observed when reallocating MVPA to the same behaviours (for example, replacing MVPA with sedentary time: 2.50 (0.85–4.18) %). Replacing prolonged with non-prolonged sedentary time was not associated with cfPWV (−0.27 (−0.86 to 0.32) %). In short sleepers, reallocating sedentary time to the sleep period was favourable (−1.96 (−3.74 to −0.15) %). ConclusionsIncreasing or at least maintaining MVPA appears to be important for arterial health in adults. Extending sleep in habitually short sleepers, specifically by redistributing sedentary time, may also be important.

Relationship Between Physical Activity and Estimated Glomerular Filtration Rate in Renal Transplant Recipients: A Cross-sectional Study Analyzing Isotemporal Substitution Model

Successful renal transplantation reduces mortality rates. However, the decline in the estimated glomerular filtration rate (eGFR) after transplantation is strongly associated with premature mortality in renal transplant recipients (RTRs). Physical activity (PA) is a modifiable lifestyle factor with the potential to maintain or improve eGFR. However, the effects of the type or intensity of PA and sedentary behavior (SB) on eGFR in RTRs remain unclear. The purpose of this study was to clarify the association between accelerometry-measured PA and SB and eGFR in RTRs using isotemporal substitution (IS) analysis. A total of 82 renal transplant outpatients participated in this cross-sectional study, among which 65 (average age, 56.9 years; average time post-transplant, 83.0 months) were finally analyzed. All RTRs wore a triaxial accelerometer to measure PA for seven consecutive days. The measured PA was classified based on intensity into light PA (LPA), moderate-to-vigorous PA (MVPA), and SB. The association of each type of PA with eGFR was examined using multi-regression analyses of single-factor, partition, and IS models. The IS model was applied to examine the estimated effects of substituting 30 min of SB with an equal amount of time of LPA or MVPA on eGFR. The partition model showed that MVPA was an independent explanatory variable for eGFR (β = 5.503, p < 0.05), and the IS model identified that the substitution of time spent in SB with MVPA led to improvements in eGFR (β = 5.902, p < 0.05). The present study suggests that MVPA has an independent and positive association with eGFR, and replacing 30 min of SB with MVPA after renal transplantation might lead to the maintenance or improvement of eGFR in RTRs.

Moderate-to-vigorous physical activity and sedentary behavior are independently associated with renal function: a cross-sectional study.

Little is known about whether insufficient moderate-to-vigorous physical activity (MVPA) and longer sedentary behavior (SB) are independently associated with estimated glomerular filtration rate (eGFR) and CKD, whether they interact with known risk factors for CKD, and the effect of replacing sedentary time with an equivalent duration of physical activity on kidney function. We examined the cross-sectional association of MVPA and SB with eGFR and CKD in 66,603 Japanese cohort study in 14 areas from 2004 to 2013. MVPA and SB were estimated using a self-reported questionnaire, and CKD was defined as eGFR<60 mL/min/1.73 m2. Multiple linear regression analyses, logistic regression analyses, and an isotemporal substitution model were applied. After adjusting for potential confounders, higher MVPA and longer SB were independently associated with higher eGFR (Pfor trend MVPA<0.0001) and lower eGFR (Pfor trend SB<0.0001), and a lower odds ratio (OR) of CKD (adjusted OR of MVPA≥20 MET·h/day: 0.76 [95%CI: 0.68-0.85] compared to MVPA<5 MET·h/day) and a higher OR of CKD (adjusted OR of SB≥16 h/day: 1.81 [95%CI: 1.52-2.15] compared to SB<7 h/day), respectively. The negative association between MVPA and CKD was stronger in men, and significant interactions between sex and MVPA were detected. Replacing 1 hour of SB with 1 hour of physical activity was associated with about 3 to 4% lower OR of CKD. These findings indicate that replacing SB with physical activity may benefit kidney function, especially in men, adding to the possible evidence on CKD prevention.

Exchanging screen for non-screen sitting time or physical activity might attenuate depression and anxiety: A cross-sectional isotemporal analysis during early pandemics in South America.

To examine the theoretical substitutions of screen exposure, non-screen sitting time, moderate and vigorous physical activity with depressive and anxiety symptoms in South American adults during the COVID-19 pandemic. A cross-sectional study during the first months of the COVID-19 pandemic with data from 1981 adults from Chile, Argentina, and Brazil. Depressive and anxiety symptoms were assessed using the Beck Depression and Anxiety Inventories. Participants also reported physical activity, sitting time, screen exposure, sociodemographic, and tobacco use data. Isotemporal substitution models were created using multivariable linear regression methods. Vigorous physical activity, moderate physical activity, and screen exposure were independently associated with depression and anxiety symptoms. In adjusted isotemporal substitution models, replacing 10 min/day of either screen exposure or non-screen sitting time with any intensity of physical activity was associated with lower levels of depressive symptoms. Improvements in anxiety symptoms were found when reallocating either screen exposure or non-screen sitting time to moderate physical activity. Furthermore, replacing 10 min/day of screen exposure with non-screen sitting time was beneficially associated with anxiety (B = -0.033; 95 % CI = -0.059, -0.006) and depression (B = -0.026; 95 % CI = -0.050, -0.002). Replacement of screen exposure with any intensity of physical activity or non-screen sitting time could improve mental health symptoms. Strategies aiming to reduce depressive and anxiety symptoms highlight physical activity promotion. However, future interventions should explore specific sedentary behaviors as some will relate positively while others negatively.

0204 Associations of Reallocating Sedentary or Activity Time to Sleep on Body Weight in Postpartum Women

Abstract Introduction In the postpartum period, decreased sleep time is associated with increased postpartum weight retention. Increasing sleep time in the postpartum period may be beneficial; however, increasing total sleep time will reduce the time available for light physical activity (LPA), moderate to vigorous activity (MVPA), or sedentary behavior (SED). Therefore, the purpose of this study was to examine the associations of reallocating time in SED, MVPA, and LPA to sleep with body weight in postpartum women. Methods Women (n=130) who gave birth to a singleton infant at ≥37 weeks gestation participated in the study. At 6-8 weeks, 6 months, and 12 months postpartum wrist actigraphy was used to measure total sleep time and hip actigraphy was used to measure SED, LPA, and MVPA. Women were instructed to wear the monitors for 7 days and maintain their normal daily activities. Weight was measured at each timepoint using a calibrated scale. Isotemporal substitution models were preformed to examine the association of reallocating time to sleep from SED, LPA, and MVPA on body weight. Results At 6-8 weeks, reallocating ten minutes of SED or MVPA to sleep was associated with a -0.54 kg (p=0.0223) and -3.33 kg (p=0.0091) change in body weight, respectively. At 6 months, reallocating ten minutes of SED or MVPA to sleep was associated with a -0.931 kg (p=0.0069) and -2.97 kg (p=0.0434) change in body weight, respectively. At 12 months, reallocating ten minutes of SED to sleep was associated with a -1.21 kg (p=0.0166) change in body weight. Reallocating time from MVPA to sleep was not associated with changes in body weight at 12 months. Reallocating time from LPA to sleep was not associated with changes in body weight at any timepoint. Conclusion Throughout the first year postpartum, reallocating time from SED to sleep was associated with decreases in body weight. Surprisingly, reallocating time from MVPA to sleep was also associated with a decrease in body weight at 6-8 weeks and 6 months postpartum. These results suggest the relative importance of the behaviors comprising the 24-hour day to body weight may be changing over the first year postpartum. Support (if any) NIH Grant R21MD012740

Defecation Habits in Preschoolers Are Associated with Physical Activity: A Cross-Sectional and Isotemporal Substitution Analysis.

There is a lack of research on the relationship between defecation habits (DF) and physical activity (PA) in preschoolers. This study aimed to clarify the relationship between sedentary behaviour (SB), PA time, and DF in preschoolers and to estimate the effect of DF replacement in an isotemporal substitution (IS) model. The participants included 166 children (aged 4-6 years) attending childcare facilities. PA was measured using an accelerometer to calculate the daily activity and wearing time for SB, light-intensity physical activity (LPA), and moderate-to-vigorous-intensity physical activity (MVPA). DF were classified based on defecation frequency and timing. A multinomial logistic regression analysis was used for the IS model. One-way analysis of variance detected significant differences in MVPA between the DF groups (F(2) = 3.12, p < 0.05). According to the analysis results of the IS model, replacing 5 min of SB with MVPA resulted in improved DF (odds ratio [OR], 0.89; 95% confidence interval [CI], 0.81-0.97). Conversely, replacing 5 min of MVPA with SB worsened DF (OR, 1.13; 95% CI, 1.03-1.23). The findings suggest that PA is associated with DF among preschoolers. It also indicates that replacing SB with MVPA could help improve DF in children.