Sedentary Time in Relation to Cardio-Metabolic Risk Factors
Sedentary Time in Relation to Cardio-Metabolic Risk Factors
Background Sedentary behaviour has been proposed to be detrimentally associated with cardio-metabolic risk independently of moderate to vigorous physical activity (MVPA). However, it is unclear how the choice of sedentary time (ST) indicator may influence such associations. The main objectives of this study were to examine the associations between ST and a set of cardio-metabolic risk factors [waist, body mass index (BMI), systolic and diastolic blood pressure, total and high-density lipoprotein cholesterol, glycated haemoglobin] and whether these associations differ depending upon whether ST is assessed by self-report or objectively by accelerometry.
Methods Multiple linear regression was used to examine the above objectives in a cross-sectional study of 5948 adults (2669 men) aged 16–65 years with self-reported measures of television time, other recreational sitting and occupational sitting or standing. In all, 1150 (521 men) participants had objective (accelerometry) data on ST as well.
Results Total self-reported ST showed multivariable-adjusted (including for MVPA) associations with BMI [(unstandardized beta coefficients corresponding to the mean difference per 10 min/day greater ST: 0.035 kg/m; 95% CI: 0.027–0.044), waist circumference (0.083 cm; 0.062–0.105), systolic (0.024 mmHg; 0.000–0.049) and diastolic blood pressure (0.023 mmHg; 0.006–0.040) and total cholesterol (0.004 mmol/l; 0.001–0.006)]. Similar associations were observed for TV time, whereas non-TV self-reported ST showed consistent associations with the two adiposity proxies (BMI/waist circumference) and total cholesterol. Accelerometry-assessed ST was only associated with total cholesterol (0.010 mmol/l; 0.001–0.018).
Conclusions In this study, ST was associated consistently with cardio-metabolic risk only when it was measured by self-report.
An emerging body of evidence consistently suggests that excessive sedentary behaviour, as characterized by activities involving sitting, may be linked to increased risk for obesity, dyslipidemia and impaired glucose metabolism, independently of moderate to vigorous physical activity (MVPA) participation.
Recent prospective studies have shown associations between greater amounts of time spent in activities involving sitting and increased incidence of cardiovascular disease and overall mortality. Greater time spent in television (TV) viewing or other screen-based recreation has gained particular attention. A recent meta-analysis concluded that prolonged TV viewing is associated with increased risk of cardio-metabolic disease and death. Nevertheless, TV viewing behaviour remains poorly understood, and its associations with adverse outcomes might be due to a true causal effect of sedentary behaviour, an association with other unhealthy behaviours (e.g. unhealthy food snacking) that are commonly related to TV viewing or the influence of TV advertisements for unhealthy foods. In a sample of Australian adults, TV viewing was a robust marker of overall sedentary time (ST) (assessed by self-report) in women, but not in men. Greater time spent watching TV has been associated with obesity in many studies, and it is possible that this association explains associations with other cardio-metabolic risk factors and events. We have previously found that body mass index (BMI) explains approximately 12% of the relationship between TV viewing and other screen-based entertainment and cardiovascular disease (CVD) risk.
To date, the majority of studies looking at the associations between markers of ST and cardio-metabolic outcomes have relied solely on self-reported measures. In order to better understand the association between ST and cardio-metabolic risk, it is valuable to combine both self-reported (which can provide contextual information, such as whether the individual is watching TV when sedentary, which is not possible to obtain with accelerometry) and objective measures (using movement sensors, which can provide an accurate assessment of total time being inactive—primarily sitting). We are unaware of any studies that have compared associations for cardio-metabolic outcomes using both of these methods.
The aim of this study was to investigate the associations between ST and cardio-metabolic risk in working age adults. The specific objectives were to examine: (i) whether any observed associations differ between self-report and objectively assessed ST, (ii) whether any observed associations between self-reported ST and the examined cardio-metabolic outcomes differ by ST indicator (TV, other leisure time sitting, etc.), (iii) whether any observed associations are independent of MVPA and (iv) whether any observed associations between ST and (non-adiposity) cardio-metabolic outcomes are independent of BMI and waist circumference.
Abstract and Introduction
Abstract
Background Sedentary behaviour has been proposed to be detrimentally associated with cardio-metabolic risk independently of moderate to vigorous physical activity (MVPA). However, it is unclear how the choice of sedentary time (ST) indicator may influence such associations. The main objectives of this study were to examine the associations between ST and a set of cardio-metabolic risk factors [waist, body mass index (BMI), systolic and diastolic blood pressure, total and high-density lipoprotein cholesterol, glycated haemoglobin] and whether these associations differ depending upon whether ST is assessed by self-report or objectively by accelerometry.
Methods Multiple linear regression was used to examine the above objectives in a cross-sectional study of 5948 adults (2669 men) aged 16–65 years with self-reported measures of television time, other recreational sitting and occupational sitting or standing. In all, 1150 (521 men) participants had objective (accelerometry) data on ST as well.
Results Total self-reported ST showed multivariable-adjusted (including for MVPA) associations with BMI [(unstandardized beta coefficients corresponding to the mean difference per 10 min/day greater ST: 0.035 kg/m; 95% CI: 0.027–0.044), waist circumference (0.083 cm; 0.062–0.105), systolic (0.024 mmHg; 0.000–0.049) and diastolic blood pressure (0.023 mmHg; 0.006–0.040) and total cholesterol (0.004 mmol/l; 0.001–0.006)]. Similar associations were observed for TV time, whereas non-TV self-reported ST showed consistent associations with the two adiposity proxies (BMI/waist circumference) and total cholesterol. Accelerometry-assessed ST was only associated with total cholesterol (0.010 mmol/l; 0.001–0.018).
Conclusions In this study, ST was associated consistently with cardio-metabolic risk only when it was measured by self-report.
Introduction
An emerging body of evidence consistently suggests that excessive sedentary behaviour, as characterized by activities involving sitting, may be linked to increased risk for obesity, dyslipidemia and impaired glucose metabolism, independently of moderate to vigorous physical activity (MVPA) participation.
Recent prospective studies have shown associations between greater amounts of time spent in activities involving sitting and increased incidence of cardiovascular disease and overall mortality. Greater time spent in television (TV) viewing or other screen-based recreation has gained particular attention. A recent meta-analysis concluded that prolonged TV viewing is associated with increased risk of cardio-metabolic disease and death. Nevertheless, TV viewing behaviour remains poorly understood, and its associations with adverse outcomes might be due to a true causal effect of sedentary behaviour, an association with other unhealthy behaviours (e.g. unhealthy food snacking) that are commonly related to TV viewing or the influence of TV advertisements for unhealthy foods. In a sample of Australian adults, TV viewing was a robust marker of overall sedentary time (ST) (assessed by self-report) in women, but not in men. Greater time spent watching TV has been associated with obesity in many studies, and it is possible that this association explains associations with other cardio-metabolic risk factors and events. We have previously found that body mass index (BMI) explains approximately 12% of the relationship between TV viewing and other screen-based entertainment and cardiovascular disease (CVD) risk.
To date, the majority of studies looking at the associations between markers of ST and cardio-metabolic outcomes have relied solely on self-reported measures. In order to better understand the association between ST and cardio-metabolic risk, it is valuable to combine both self-reported (which can provide contextual information, such as whether the individual is watching TV when sedentary, which is not possible to obtain with accelerometry) and objective measures (using movement sensors, which can provide an accurate assessment of total time being inactive—primarily sitting). We are unaware of any studies that have compared associations for cardio-metabolic outcomes using both of these methods.
The aim of this study was to investigate the associations between ST and cardio-metabolic risk in working age adults. The specific objectives were to examine: (i) whether any observed associations differ between self-report and objectively assessed ST, (ii) whether any observed associations between self-reported ST and the examined cardio-metabolic outcomes differ by ST indicator (TV, other leisure time sitting, etc.), (iii) whether any observed associations are independent of MVPA and (iv) whether any observed associations between ST and (non-adiposity) cardio-metabolic outcomes are independent of BMI and waist circumference.
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