Too much sitting--a health hazard

In contemporary society, prolonged sitting has been engineered into our lives across many settings, including transportation, the workplace, and the home. There is new evidence that too much sitting (also known as sedentary behavior - which involves very low energy expenditure, such as television viewing and desk-bound work) is adversely associated with health outcomes, including cardio-metabolic risk biomarkers, type 2 diabetes and premature mortality. Importantly, these detrimental associations remain even after accounting for time spent in leisure time physical activity. We describe recent evidence from epidemiological and experimental studies that makes a persuasive case that too much sitting should now be considered an important stand-alone component of the physical activity and health equation, particularly in relation to diabetes and cardiovascular risk. We highlight directions for further research and consider some of the practical implications of focusing on too much sitting as a modifiable health risk.

Sit-stand workstations: a pilot intervention to reduce office sitting time

BACKGROUND

Sitting time is a prevalent health risk among office-based workers.

PURPOSE

To examine, using a pilot study, the efficacy of an intervention to reduce office workers' sitting time.

DESIGN

Quasi-experimental design with intervention-group participants recruited from a single workplace that was physically separate from the workplaces of comparison-group participants.

SETTING/PARTICIPANTS

Office workers (Intervention, n=18; Comparison, n=14) aged 20-65 years from Brisbane, Australia; data were collected and analyzed in 2011.

INTERVENTION

Installation of a commercially available sit-stand workstation.

MAIN OUTCOME MEASURES

Changes from baseline at 1-week and 3-month follow-up in time spent sitting, standing, and stepping at the workplace and during all waking time (activPAL3 activity monitor, 7-day observation). Fasting total cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, and glucose levels were assessed at baseline and 3 months (Cholestech LDX Analyzer). Acceptability was assessed with a 5-point response scale (eight items).

RESULTS

The intervention group (relative to the comparison group) reduced sitting time at 1-week follow-up by 143 minutes/day at the workplace (95% CI= -184, -102) and 97 minutes/day during all waking time (95% CI= -144, -50). These effects were maintained at 3 months (-137 minutes/day and -78 minutes/day, respectively). Sitting was almost exclusively replaced by standing, with minimal changes to stepping time. Relative to the comparison group, the intervention group increased HDL cholesterol by an average of 0.26 mmol/L (95% CI=0.10, 0.42). Other biomarker differences were not significant. There was strong acceptability and preference for using the workstations, though some design limitations were noted.

CONCLUSIONS

This trial is the first with objective measurement and a comparison group to demonstrate that the introduction of a sit-stand workstation can substantially reduce office workers' sitting time both at the workplace and overall throughout the week.

Evidence-based intervention in physical activity: lessons from around the world

Promotion of physical activity is a priority for health agencies. We searched for reviews of physical activity interventions, published between 2000 and 2011, and identified effective, promising, or emerging interventions from around the world. The informational approaches of community-wide and mass media campaigns, and short physical activity messages targeting key community sites are recommended. Behavioural and social approaches are effective, introducing social support for physical activity within communities and worksites, and school-based strategies that encompass physical education, classroom activities, after-school sports, and active transport. Recommended environmental and policy approaches include creation and improvement of access to places for physical activity with informational outreach activities, community-scale and street-scale urban design and land use, active transport policy and practices, and community-wide policies and planning. Thus, many approaches lead to acceptable increases in physical activity among people of various ages, and from different social groups, countries, and communities.

Translation from research to practice: community dissemination of a telephone-delivered physical activity and dietary behavior change intervention

PURPOSE

To describe the process of translating an evidence-based, telephone-delivered physical activity and dietary behavior change intervention from research into practice.

DESIGN

Descriptive case study.

SETTING/SUBJECTS

Nongovernment, primary medical care-based community health organization.

INTERVENTION

Telephone-delivered intervention targeting physical activity and diet in primary medical care patients.

MEASURES/ANALYSIS

Systematic documentation of process outcomes related to intervention adoption and adaptation.

RESULTS

Research-community partnerships were critical in facilitating translation, including (1) an initial competitive advantage within a State Health Department-funded preventive health initiative; (2) advocacy to ensure the adoption of the intervention, (3) subsequent support for the adaptation of program elements to ensure fit of the program with the community organization's objectives and capacities, while maintaining feasible elements of fidelity with the original evidence-based program; (4) the integration of program management and evaluation systems within the community organization; and (5) ongoing support for staff members responsible for program delivery and evaluation. Preliminary process evaluation of the Optimal Health Program supports the acceptability and feasibility of the program within community practice.

CONCLUSIONS

INTERVENTION characteristics central to adoption can be influenced by research-community partnerships. It is likely that evidence-based interventions will need to be adapted for delivery within the real world. Researchers should endeavor to provide training and support to ensure, as much as possible, fidelity with the original program, and that the relevant adaptations are evidence based.

Adverse associations of increases in television viewing time with 5-year changes in glucose homoeostasis markers: the AusDiab study

BACKGROUND

Television viewing time is associated cross-sectionally with abnormal glucose tolerance and diabetes risk; however, the impact of changes in television viewing time on glycaemic measures is less understood. We examined relationships of 5-year change in television viewing time with 5-year change in glucose homeostasis markers.

METHODS

Participants in the Australian Diabetes, Obesity and Lifestyle study with data available at the 1999-2000 baseline and the 2004-2005 follow-up were included (4870; 45% men). Television viewing time (h/week) was assessed by questionnaire. Fasting plasma glucose, serum insulin and 2-h plasma glucose were obtained from an oral glucose tolerance test. Beta-cell function and insulin resistance were ascertained using the homeostasis model assessment 2-calculator. Associations of change in television viewing time with changes in glucose homeostasis markers were examined using linear regression models [β-coefficients (95% CI)]. Adjustments included baseline measures of age, television viewing time and glycaemic marker, and baseline and 5-year change in diet quality, energy intake, physical activity and waist circumference.

RESULTS

For every 5-h per week increase in television viewing time from baseline to 5-year follow-up, changes in glucose homeostasis markers were observed: among women there was a significant increase in fasting plasma glucose [0.01 (0.00-0.02) mmol/l] insulin resistance [0.03 (0.01-0.05)] and insulin secretion [1.07 (0.02-2.12) %]; insulin levels increased [men: 1.20 (0.30-2.09); women: 1.06 (0.32-1.80) pmol/l]; in men, 2-h plasma glucose levels increased [0.06 (0.01-0.1) mmol/l].

CONCLUSION

Five-year increases in television viewing time were associated adversely with changes in glucose homeostasis markers. These findings add to earlier cross-sectional evidence that television viewing time can be associated with biomarkers of diabetes risk.

Perceived neighborhood environmental attributes associated with adults' transport-related walking and cycling: Findings from the USA, Australia and Belgium

Background

Active transportation has the potential to contribute considerably to overall physical activity levels in adults and is likely to be influenced by neighborhood-related built environment characteristics. Previous studies that examined the associations between built environment attributes and active transportation, focused mainly on transport-related walking and were conducted within single countries, limiting environmental variability. We investigated the direction and shape of relationships of perceived neighborhood attributes with transport-related cycling and walking in three countries; and examined whether these associations differed by country and gender.

Methods

Data from the USA (Baltimore and Seattle), Australia (Adelaide) and Belgium (Ghent) were pooled. In total, 6,014 adults (20–65 years, 55.7% women) were recruited in high-/low-walkable and high-/low-income neighborhoods. All participants completed the Neighborhood Environmental Walkability Scale and the International Physical Activity Questionnaire. Generalized additive mixed models were used to estimate the strength and shape of the associations.

Results

Proximity to destinations, good walking and cycling facilities, perceiving difficulties in parking near local shopping areas, and perceived aesthetics were included in a ‘cyclability’ index. This index was linearly positively related to transport-related cycling and no gender- or country-differences were observed. The ‘walkability’ index consisted of perceived residential density, land use mix access, proximity of destinations and aesthetics. A non-linear positive relationship with transport-related walking was found. This association was stronger in women than in men, and country-specific associations were identified: the strongest association was observed in Seattle, the weakest in Adelaide. In Ghent, the association weakened at higher levels of walkability.

Conclusions

For cycling, consistent correlates were found in the three countries, but associations were less straightforward for transport-related walking. Moreover, the identified neighborhood environmental correlates were different for walking compared to cycling. In order to further clarify the shape of these associations and reach more specific international guidelines for developing walkable and bikeable neighborhoods, future studies should include even more countries to maximize environmental variability.

Physical activity, family history of diabetes and risk of developing hyperglycaemia and diabetes among adults in Mainland China

AIMS

To investigate the joint influence of physical activity and family history of diabetes on the subsequent risk of developing hyperglycaemia and Type 2 diabetes among Chinese adults.

METHODS

A prospective community-based cohort study was conducted among adults aged 35 years and older during 2004-2007 in Nanjing, China. Four communities (three urban and one rural) were randomly selected from 11 urban districts and two rural counties. Hyperglycaemia and Type 2 diabetes were defined using World Health Organization criteria based on fasting blood glucose concentration and physicians' diagnosis, respectively. Physical activity, parental diabetes history, and other important covariates were assessed at baseline and in the third-year follow-up survey.

RESULTS

At study conclusion data were collected from 3031 participants (follow-up rate 81.3%). The 3-year cumulative incidence of hyperglycaemia and Type 2 diabetes was 6.2% and 2.4%, respectively. After adjustment for potential confounding variables, compared with those with positive family history and insufficient physical activity, the adjusted relative risk ratio (95% CI) of developing hyperglycaemia was 0.19 (0.02, 1.51) for participants with sufficient physical activity and a positive family history; 0.55 (0.31, 0.97) for participants with insufficient physical activity and a negative family history; and 0.36 (0.19, 0.70) for participants with sufficient physical activity but a negative family history. Participants who had a negative family history and insufficient physical activity were also less likely to develop Type 2 diabetes (RRR = 0.28; 0.14, 0.54), and participants with a negative family history and sufficient physical activity were the least likely to develop Type 2 diabetes (0.23; 0.10, 0.56).

CONCLUSIONS

Sufficient physical activity and negative family history of diabetes may jointly reduce the risk of developing hyperglycaemia and Type 2 diabetes in Chinese adults.

Breaking up prolonged sitting reduces postprandial glucose and insulin responses

OBJECTIVE

Observational studies show breaking up prolonged sitting has beneficial associations with cardiometabolic risk markers, but intervention studies are required to investigate causality. We examined the acute effects on postprandial glucose and insulin levels of uninterrupted sitting compared with sitting interrupted by brief bouts of light- or moderate-intensity walking.

RESEARCH DESIGN AND METHODS

Overweight/obese adults (n = 19), aged 45-65 years, were recruited for a randomized three-period, three-treatment acute crossover trial: 1) uninterrupted sitting; 2) seated with 2-min bouts of light-intensity walking every 20 min; and 3) seated with 2-min bouts of moderate-intensity walking every 20 min. A standardized test drink was provided after an initial 2-h period of uninterrupted sitting. The positive incremental area under curves (iAUC) for glucose and insulin (mean [95% CI]) for the 5 h after the test drink (75 g glucose, 50 g fat) were calculated for the respective treatments.

RESULTS

The glucose iAUC (mmol/L) · h after both activity-break conditions was reduced (light: 5.2 [4.1-6.6]; moderate: 4.9 [3.8-6.1]; both P < 0.01) compared with uninterrupted sitting (6.9 [5.5-8.7]). Insulin iAUC (pmol/L) · h was also reduced with both activity-break conditions (light: 633.6 [552.4-727.1]; moderate: 637.6 [555.5-731.9], P < 0.0001) compared with uninterrupted sitting (828.6 [722.0-950.9]).

CONCLUSIONS

Interrupting sitting time with short bouts of light- or moderate-intensity walking lowers postprandial glucose and insulin levels in overweight/obese adults. This may improve glucose metabolism and potentially be an important public health and clinical intervention strategy for reducing cardiovascular risk.

Identifying sedentary time using automated estimates of accelerometer wear time

PURPOSE

The authors evaluated the accuracy of three automated accelerometer wear-time estimation algorithms against self-report. Direct effects on sedentary time (<100 cpm) and indirect effects on moderate-to-vigorous physical activity (MVPA, ≥1952 cpm) time were examined.

METHODS

A subsample from the 2004/2005 Australian Diabetes, Obesity and Lifestyle Study (n=148) completed activity logs and wore accelerometers for a total of 987 days. A published algorithm that allows movement within non-wear periods (Algorithm 1) was compared with one that allows less movement (Algorithm 2) or no movement (Algorithm 3). Implications for population estimates were examined using 2003/2004 US National Health and Nutrition Examination Survey data.

RESULTS

Mean difference per day between the criterion and estimated wear time was negligible for all three algorithms (≤11 min), but 95% limits of agreement (LOA) were wide (±≥2 h). Respectively, the algorithms (1, 2 and 3) misclassified sedentary time as non-wear on 31.9%, 19.4% and 18% of days and misclassified non-wear time as sedentary on 42.8%, 43.7% and 51.3% of days. Use of Algorithm 2 (compared with Algorithm 1) affected population estimates of sedentary time (higher by 20 min/day) but not MVPA time. Agreement between Algorithms 1 and 2 was good for MVPA time (mean difference -0.08, LOA: -2.08, 1.91 min), but not for wear time or sedentary time.

CONCLUSION

Accelerometer wear time can be estimated accurately on average; however, misclassification can be substantial for individuals. Algorithm choice affects estimates of sedentary time. Allowing very limited movement within non-wear periods can improve accuracy.

Sedentary behaviors of adults in relation to neighborhood walkability and income

OBJECTIVE

Sedentary (sitting) time is a newly identified risk factor for obesity and chronic diseases, which is behaviorally and physiologically distinct from lack of physical activity. To inform public health approaches to influencing sedentary behaviors, an understanding of correlates is required.

METHODS

Participants were 2,199 adults aged 20-66 years living in King County/Seattle, WA, and Baltimore, MD, regions, recruited from neighborhoods high or low on a "walkability index" (derived from objective built environment indicators) and having high or low median incomes. Cross-sectional associations of walkability and income with total sedentary time (measured by accelerometers and by self-report) and with self-reported time in seven specific sitting-related behaviors were examined.

RESULTS

Neighborhood walkability and income were unrelated to measures of total sitting time. Lower neighborhood walkability was significantly associated with more driving time (difference of 18.2 min/day, p < .001) and more self-reported TV viewing (difference of 14.5 min/day, p < .001). Residents of higher income neighborhoods reported more computer/Internet and reading time, and they had more objectively measured sedentary time.

CONCLUSIONS

Neighborhood walkability was not related to total sedentary time but was related to two specific sedentary behaviors associated with risk for obesity-driving time and TV viewing time. Future research could examine how these prevalent and often prolonged sedentary behaviors mediate relationships between neighborhood walkability and overweight/obesity. Initiatives to reduce chronic disease risk among residents of both higher-and lower-income low-walkable neighborhoods should include a focus on reducing TV viewing time and other sedentary behaviors and enacting policies that can lead to the development or redevelopment of more-walkable neighborhoods. (PsycINFO Database Record (c) 2012 APA, all rights reserved).

Joint impact of physical activity and family history on the development of diabetes among urban adults in Mainland China: a pooled analysis of community-based prospective cohort studies

To examine the joint influences of physical activity (PA) and family history (FH) of diabetes on subsequent type 2 diabetes (T2D), the authors pooled and analyzed data from 2 community-based urban adult prospective cohort studies in 2011 in Nanjing, China. Among 4550 urban participants, the 3-year cumulative incidence of T2D was 5.1%. After adjustment for potential confounders, compared with those with FH+ and insufficient PA, the adjusted odds ratio (95% confidence interval) of developing T2D was 0.42 (0.18, 0.98) for participants with sufficient PA and FH+, 0.32 (0.22, 0.46) for participants with insufficient PA and FH-, and 0.15 (0.08, 0.28) for participants with sufficient PA and FH-. Such significant graduated associations between PA/FH and risk of developing T2D were also identified in either men or women, separately. Sufficient PA and FH- may jointly reduce the risk of developing T2D in urban Chinese adults.

Measuring older adults' sedentary time: reliability, validity, and responsiveness

PURPOSE

With evidence that prolonged sitting has deleterious health consequences, decreasing sedentary time is a potentially important preventive health target. High-quality measures, particularly for use with older adults, who are the most sedentary population group, are needed to evaluate the effect of sedentary behavior interventions. We examined the reliability, validity, and responsiveness to change of a self-report sedentary behavior questionnaire that assessed time spent in behaviors common among older adults: watching television, computer use, reading, socializing, transport and hobbies, and a summary measure (total sedentary time).

METHODS

In the context of a sedentary behavior intervention, nonworking older adults (n = 48, age = 73 ± 8 yr (mean ± SD)) completed the questionnaire on three occasions during a 2-wk period (7 d between administrations) and wore an accelerometer (ActiGraph model GT1M) for two periods of 6 d. Test-retest reliability (for the individual items and the summary measure) and validity (self-reported total sedentary time compared with accelerometer-derived sedentary time) were assessed during the 1-wk preintervention period, using Spearman (ρ) correlations and 95% confidence intervals (CI). Responsiveness to change after the intervention was assessed using the responsiveness statistic (RS).

RESULTS

Test-retest reliability was excellent for television viewing time (ρ (95% CI) = 0.78 (0.63-0.89)), computer use (ρ (95% CI) = 0.90 (0.83-0.94)), and reading (ρ (95% CI) = 0.77 (0.62-0.86)); acceptable for hobbies (ρ (95% CI) = 0.61 (0.39-0.76)); and poor for socializing and transport (ρ < 0.45). Total sedentary time had acceptable test-retest reliability (ρ (95% CI) = 0.52 (0.27-0.70)) and validity (ρ (95% CI) = 0.30 (0.02-0.54)). Self-report total sedentary time was similarly responsive to change (RS = 0.47) as accelerometer-derived sedentary time (RS = 0.39).

CONCLUSIONS

The summary measure of total sedentary time has good repeatability and modest validity and is sufficiently responsive to change suggesting that it is suitable for use in interventions with older adults.

Habitual active transport, TV viewing and weight gain: a four year follow-up study

OBJECTIVES

To examine the associations of TV viewing time and domain-specific physical activity with weight change; to determine whether domain-specific physical activity moderates the potential association of TV viewing time with weight change.

METHODS

We used four-year longitudinal data (baseline: 2003-2004, follow-up: 2007-2008) on 969 adults from selected neighborhoods in Adelaide, Australia (Age: 48.6 ± 10.6 years, 61% females). Mixed models examined four-year weight change as the dependent variable, with TV viewing time, habitual transport and past week domain-specific physical activity at baseline as independent variables.

RESULTS

On average, participants gained 1.6 kg over four years. TV viewing time at baseline was positively associated with weight gain at follow-up. Each additional hour of TV viewing was associated with 0.24-0.27 kg of extra weight gain. This relationship was not moderated by recent recall of transport, leisure-time, and occupational physical activity, but was moderated by habitual transport: an additional hour of TV viewing time at baseline was significantly associated with an extra weight gain of 0.65 kg at follow-up among those who were inactive in everyday transport; TV time was not significantly associated with weight change among those who were regularly active in transport.

CONCLUSION

Habitual active transport may protect adults against risk of weight gain associated with prolonged TV viewing time.

Associations between perceived neighborhood environmental attributes and adults' sedentary behavior: findings from the U.S.A., Australia and Belgium

Sedentary behaviors are associated with multiple health problems, independently of physical activity. Neighborhood environment attributes might influence sedentary behaviors, but few studies have investigated these relationships. Moreover, all previous studies have been conducted within single countries, limiting environmental variability. We investigated the shape of associations between perceived neighborhood environment attributes and sedentary behavior in three countries; and whether these associations differed by country and gender. Data from U.S.A. (Seattle and Baltimore regions), Australia (Adelaide) and Belgium (Ghent) were pooled. Data collection took place between 2002 and 2008. In total, 6014 adults (20-65 years, 55.7% women) were recruited in high-/low-walkability and high-/low-income neighborhoods. All participants completed the International Physical Activity Questionnaire (domain-specific physical activity, transport-related sitting and overall time spent sitting) and the Neighborhood Environmental Walkability Scale (environmental perceptions). The number of destinations within a 20 min walk from home, perceiving few cul-de-sacs, good walking and cycling facilities, and traffic safety were included in an index of motorized transport correlates. This index was linearly negatively associated with motorized transport time, so the higher the scores on the index (more activity-friendliness), the lower the amount of motorized transport. No gender- or country-differences were identified. Perceived aesthetics and proximity of destinations were included in an index of overall sitting time correlates. A linear negative relationship with overall sitting time was found, but associations were stronger for men and not significant in Belgian adults. In conclusion, consistent and expected correlates were found for motorized transport in the three countries, but results were less clear for overall sitting time. Future studies should include even more countries to maximize environmental variability, but present findings suggest that neighborhoods may be designed to improve health through supporting more active and less sedentary transportation, which can be expected to have health benefits.

Validity of self-reported measures of workplace sitting time and breaks in sitting time

PURPOSE

To understand the prevalence and potential health effect of prolonged workplace sedentary (sitting) time, valid measures are required. Here, we examined the criterion validity of a brief self-reported measure of workplace sitting time and breaks in sitting time.

METHODS

An interviewer-administered questionnaire was used to assess workplace sitting time (h·d(-1)) and breaks from sitting per hour at work in a convenience sample of 121 full-time workers (36% men, mean age = 37 yr, 53% office based). These self-reported measures were compared with accelerometer-derived sedentary time (hours per day, <100 counts per minute) and breaks per sedentary hour (number of times, ≥100 counts per minute) during work hours.

RESULTS

Self-reported sitting time was significantly correlated with accelerometer-derived sedentary time (Pearson r = 0.39, 95% confidence interval = 0.22-0.53), with an average sitting time 0.45 h·d(-1) higher than average sedentary time. Bland-Altman plots and regression analysis showed positive associations between the difference in sitting and sedentary time and the average of sitting and sedentary time (mean difference = -2.75 h + 0.47 × average sitting and sedentary time; limits of agreement = ±2.25 h·d(-1)). The correlation of self-reported breaks per sitting hour with accelerometer-derived breaks per sedentary hour was also statistically significant (Spearman rs = 0.26, 95% confidence interval = 0.11-0.44).

CONCLUSIONS

This study is the first to examine the criterion validity of an interviewer-administered questionnaire measure of workplace sitting time and breaks in sitting time using objective criterion measures. The workplace sitting measure has acceptable properties for use in observational studies concerned with sedentary behavior in groups of workers; however, the wide limits of agreement suggest caution in estimating individuals' sitting time with high precision. Using self-reported measures to capture patterns of workplace sitting (such as breaks in sitting time) requires further development.

Environmental and psychosocial correlates of accelerometer-assessed and self-reported physical activity in Belgian adults

BACKGROUND

Despite the well-known benefits of physical activity (PA) on overall health, the majority of the adult population does not engage in sufficient PA. To develop effective interventions to increase PA, it is necessary to understand the most important PA correlates and to investigate whether correlates are similar in different population subgroups.

PURPOSE

This study examined associations between physical environmental perceptions and self-reported and objectively assessed PA in Belgian adults. Moreover, associations between psychosocial factors and PA, and the moderating effects of sociodemographic factors were investigated.

METHOD

A sample of 1,200 Belgian adults (20-65 years; 47.9% males) completed a survey measuring sociodemographic variables and psychosocial correlates, the Neighborhood Environmental Walkability Scale and the long-version International Physical Activity Questionnaire. They wore an accelerometer for 7 days.

RESULTS

Perceiving neighborhoods to be high walkable (high residential density, high land use mix access, and high land use mix diversity) and recreation facilities to be convenient, and the availability of home PA equipment were the most consistent physical environmental correlates of PA. The strongest psychosocial correlates were social support from friends and family and self-efficacy. The psychosocial associations were most consistent for self-reported leisure-time PA and less clear for self-reported active transportation and accelerometer-assessed PA. Few significant sociodemographic moderators were found.

CONCLUSION

Both physical environmental and psychosocial factors were associated with PA in adults, with psychosocial factors being important especially for leisure-time PA. Correlates of PA were similar regardless of gender, age, or socio-economic status, so interventions to change these factors could have population-wide effects.

Television viewing time is associated with overweight/obesity among older adults, independent of meeting physical activity and health guidelines

Background

Previous studies have shown associations of sedentary behavior with cardiovascular risk, independent of moderate-to-vigorous physical activity (MVPA). However, few studies have focused on older adults. This study examined the joint associations of television (TV) viewing time and MVPA with overweight/obesity among Japanese older adults.

Methods

A population-based, cross-sectional mail survey was used to collect self-reported height, weight, time spent in TV viewing, and MVPA from 1806 older adults (age: 65–74 years, men: 51.1%). Participants were classified into 4 categories according to TV viewing time (dichotomized into high and low around the median) and MVPA level (dichotomized into sufficient and insufficient by the physical activity guideline level of ≥150 minutes/week). Odds ratios (ORs) for overweight/obesity (body mass index ≥25 kg/m²) were calculated according to the 4 TV/MVPA categories, adjusting for potential confounders.

Results

Of all participants, 20.1% were overweight/obese. The median TV viewing time (25th, 75th percentile) was 840 (420, 1400) minutes/week. As compared with the reference category (high TV/insufficient MVPA), the adjusted ORs (95% CI) of overweight/obesity were 0.93 (0.65, 1.34) for high TV/sufficient MVPA, 0.58 (0.37, 0.90) for low TV/insufficient MVPA, and 0.67 (0.47, 0.97) for low TV/sufficient MVPA.

Conclusions

In this sample of older adults, spending less time watching TV, a predominant sedentary behavior, was associated with lower risk of being overweight or obese, independent of meeting physical activity guidelines. Further studies using prospective and/or intervention designs are warranted to confirm the presently observed effects of sedentary behavior, independent of physical activity, on the health of older adults.

Hours spent and energy expended in physical activity domains: results from the Tomorrow Project cohort in Alberta, Canada

Background

Knowledge of adult activity patterns across domains of physical activity is essential for the planning of population-based strategies that will increase overall energy expenditure and reduce the risk of obesity and related chronic diseases. We describe domain-specific hours of activity and energy expended among participants in a prospective cohort in Alberta, Canada.

Methods

The Past Year Total Physical Activity Questionnaire was completed by 15,591 Tomorrow Project^® participants, between 2001 and 2005 detailing physical activity type, duration, frequency and intensity. Domain-specific hours of activity and activity-related energy expenditure, expressed as a percent of total energy expenditure (TEE) (Mean (SD); Median (IQR)) are reported across inactive (<1.4), low active (1.4 to 1.59), active (1.6 to 1.89) and very active (≥ 1.9) Physical Activity Level (PAL = TEE:REE) categories.

Results

In very active women and amongst all men except those classified as inactive, activity-related energy expenditure comprised primarily occupational activity. Amongst inactive men and women in active, low active and inactive groups, activity-related energy expenditure from household activity was comparable to, or exceeded that for occupational activity. Leisure-time activity-related energy expenditure decreased with decreasing PAL categories; however, even amongst the most active men and women it accounted for less than 10 percent of TEE. When stratified by employment status, leisure-time activity-related energy expenditure was greatest for retired men [mean (SD): 10.8 (8.5) percent of TEE], compared with those who were fully employed, employed part-time or not employed. Transportation-related activity was negligible across all categories of PAL and employment status.

Conclusion

For the inactive portion of this population, active non-leisure activities, specifically in the transportation and occupational domains, need to be considered for inclusion in daily routines as a means of increasing population-wide activity levels. Environmental and policy changes to promote active transport and workplace initiatives could increase overall daily energy expenditure through reducing prolonged sitting time.

Associations of objectively-assessed physical activity and sedentary time with depression: NHANES (2005-2006)

BACKGROUND

Studies provide conflicting evidence for the protective effects of moderate-to-vigorous-intensity physical activity on depression. Recent evidence suggests that sedentary behaviors may also be associated with depression.

PURPOSE

To examine the associations of accelerometer-derived moderate-to-vigorous-intensity physical activity and sedentary time with depression among a population-based sample.

METHODS

Cross-sectional study using 2,862 adults from the 2005-2006 US National Health and Nutrition Examination Survey. ActiGraph accelerometers were used to derive both moderate-to-vigorous-intensity physical activity and sedentary time.

RESULTS

Depression occurred in 6.8% of the sample. For moderate-to-vigorous-intensity physical activity, compared with those in quartile 1 (least active), significantly lower odds of depression were observed for those participants in quartiles 2 (OR=0.55, 95% CI, 0.34 to 0.89), 3 (OR=0.49, 95% CI, 0.26 to 0.93), and 4 (most active) (OR=0.37, 95% CI, 0.20 to 0.70) (p for trend p<0.01). In overweight/obese participants only, those in quartile 4 (most sedentary) had significantly higher odds for depression than those in quartile 1 (least sedentary) [quartile 3 vs 1 (OR=1.94, 95% CI, 1.01 to 3.68) and 4 vs 1 (OR=3.09, 95% CI, 1.25 to 7.68)].

CONCLUSION

The current study identified lower odds of depression were associated with increasing moderate-to-vigorous-intensity physical activity and decreasing sedentary time, at least within overweight/obese adults.

Abdominal obesity, TV-viewing time and prospective declines in physical activity

OBJECTIVE

To examine the prospective associations of baseline abdominal obesity and TV-viewing time with five-year reductions in leisure-time physical activity level.

METHODS

We used data from the Australian Diabetes, Obesity and Lifestyle Study (AusDiab), a nationally representative population-based cohort study with measures collected in 1999-2000 and 2004-2005. Abdominal obesity was determined by waist circumference and TV-viewing time and physical activity level were assessed using established interviewer-administered questionnaires.

RESULTS

Among 2,191 men and 2,650 women aged ≥ 25years, odds ratios (ORs) of 5-year reductions from sufficient to insufficient or no physical activity, and from insufficient to no physical activity were estimated with logistic regression. We adjusted for sociodemographic characteristics. The odds of reducing physical levels from baseline to the follow-up survey for obese men (34.2%) and women (38.1%), respectively were 1.40 (1.10-1.79) and 1.44 (1.16-1.80), compared to those with a normal waist circumference. Women, but not men, with higher levels of TV-viewing time had higher odds of reducing physical activity levels (8.6%; OR 1.46; 1.01-2.11), independent of abdominal obesity.

CONCLUSIONS

These findings suggest that abdominal obesity is associated with prospective reductions in physical activity level, and that high levels of TV-viewing time might have an additional adverse influence for women.

Mediators of physical activity change in a behavioral modification program for type 2 diabetes patients

BACKGROUND

Many studies have reported significant behavioral impact of physical activity interventions. However, few have examined changes in potential mediators of change preceding behavioral changes, resulting in a lack of information concerning how the intervention worked. Our purpose was to examine mediation effects of changes in psychosocial variables on changes in physical activity in type 2 diabetes patients.

METHODS

Ninety-two patients (62 ± 9 years, 30, 0 ± 2.5 kg/m(2), 69% males) participated in a randomized controlled trial. The 24-week intervention was based on social-cognitive constructs and consisted of a face-to-face session, telephone follow-ups, and the use of a pedometer. Social-cognitive variables and physical activity (device-based and self-reported) were collected at baseline, after the 24-week intervention and at one year post-baseline. PA was measured by pedometer, accelerometer and questionnaire.

RESULTS

Post-intervention physical activity changes were mediated by coping with relapse, changes in social norm, and social modeling from family members (p ≤ 0.05). One-year physical activity changes were mediated by coping with relapse, changes in social support from family and self-efficacy towards physical activity barriers (p ≤ 0.05)

CONCLUSIONS

For patients with type 2 diabetes, initiatives to increase their physical activity could usefully focus on strategies for resuming regular patterns of activity, on engaging family social support and on building confidence about dealing with actual and perceived barriers to activity.

TRIAL REGISTRATION

NCT00903500, ClinicalTrials.gov.

Relationship of television time with accelerometer-derived sedentary time: NHANES

PURPOSE

To examine the relationship of self-reported television (TV) viewing time with accelerometer-derived total sedentary time and to determine whether it differs by subgroup.

METHODS

Using data for adults (≥20 yr) from the 2003-2004 and 2005-2006 nationally representative US National Health and Nutrition Examination Surveys (NHANES; n=5738), linear regression models examined the associations of categories of self-reported TV viewing time (<1, 1, 2, 3, 4, and >5 h·d) with accelerometer-derived sedentary time (<100 counts per minute; h·d). Spearman ρ assessed the correlation between participants' rankings on the two measures. Analyses were stratified by gender, age, race/ethnicity, and, in the 2003-2004 NHANES cycle, by work status among working-aged adults (20-65 yr, n=2069).

RESULTS

TV viewing time was significantly associated with sedentary time, with positive associations for all gender, age, race/ethnicity groups, and for those not working or working part-time, but not for those in full-time work. However, correlations between rankings of the measures were only "fair" overall (ρ=0.22) and were similar for all gender and racial/ethnic groups and for those of mid- and older age but not for those of younger age (20-39 yr, ρ=0.05). In the working-aged subgroup, there was also a fair correlation between the measures for those not working (ρ=0.22) but no significant correlation for those in part-time (ρ=0.14) or full-time work (ρ=0.03).

CONCLUSIONS

Associations of TV viewing time with accelerometer-derived total sedentary time were statistically significant, but correlations were of only fair magnitude, and the strength of the relationship was not consistent across all population subgroups. These findings suggest that TV viewing time has an influence on overall sedentary time at a population level; however, measurement of sedentary time in other domains is also important.

Socio-demographic, psychosocial and home-environmental attributes associated with adults' domestic screen time

BACKGROUND

Sedentary behaviors (involving prolonged sitting time) are associated with deleterious health consequences, independent of (lack of) physical activity. To inform interventions, correlates of prevalent sedentary behaviors need to be identified. We examined associations of socio-demographic, home-environmental and psychosocial factors with adults' TV viewing time and leisure-time Internet use; and whether psychosocial and environmental correlates differed according to gender, age and educational attainment.

METHODS

This cross-sectional study was conducted in Ghent, Belgium, between March and May 2010. Respondents to a mail-out survey (n = 419; 20-65 years; mean age 48.5 [12.1] years; 47.3% men) completed a questionnaire on sedentary behaviors and their potential socio-demographic, psychosocial and home environmental correlates. Statistical analyses were performed using multiple linear regression models.

RESULTS

The independent variables explained 31% of the variance in TV viewing time and 38% of the variance in leisure-time Internet use. Higher education, greater perceived pros of and confidence about reducing TV time were negatively associated with TV viewing time; older age, higher body mass index, larger TV set size and greater perceived cons of reducing TV time showed positive associations. Perceived pros of and confidence about reducing Internet use were negatively associated with leisure-time Internet use; higher education, number of computers in the home, positive family social norms about Internet use and perceived cons of reducing Internet use showed positive associations. None of the socio-demographic factors moderated these associations.

CONCLUSIONS

Educational level, age, self-efficacy and pros/cons were the most important correlates identified in this study. If further cross-sectional and longitudinal research can confirm these findings, tailored interventions focusing on both psychosocial and environmental factors in specific population subgroups might be most effective to reduce domestic screen time.