Sedentary time in relation to cardio-metabolic risk factors: differential associations for self-report vs accelerometry in working age adults.

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(2); 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.