Reconsidering the sedentary behaviour paradigm.
OBJECTIVE
Recent literature has posed sedentary behaviour as an independent entity to physical inactivity. This study investigated whether associations between sedentary behaviour and cardio-metabolic biomarkers remain when analyses are adjusted for total physical activity.


METHODS
Cross-sectional analyses were undertaken on 4,618 adults from the 2003/04 and 2005/06 U.S. National Health and Nutrition Examination Survey. Minutes of sedentary behaviour and moderate-to-vigorous physical activity (MVPA), and total physical activity (total daily accelerometer counts minus counts accrued during sedentary minutes) were determined from accelerometry. Associations between sedentary behaviour and cardio-metabolic biomarkers were examined using linear regression.


RESULTS
Results showed that sedentary behaviour was detrimentally associated with 8/11 cardio-metabolic biomarkers when adjusted for MVPA. However, when adjusted for total physical activity, the associations effectively disappeared, except for C-reactive protein, which showed a very small, favourable association (β = -0.06) and triglycerides, which showed a very small, detrimental association (β = 0.04). Standardised betas suggested that total physical activity was consistently, favourably associated with cardio-metabolic biomarkers (9/11 biomarkers, standardized β = 0.08-0.30) while sedentary behaviour was detrimentally associated with just 1 biomarker (standardized β = 0.12).


CONCLUSIONS
There is virtually no association between sedentary behaviour and cardio-metabolic biomarkers once analyses are adjusted for total physical activity. This suggests that sedentary behaviour may not have health effects independent of physical activity.
Health and Use of Time Group, School of Health Sciences, University of South Australia, Adelaide, South Australia, Australia.
Carol
C
Maher
Health and Use of Time Group, School of Health Sciences, University of South Australia, Adelaide, South Australia, Australia.
Tim
T
Olds
Division of Population Science, Pennington Biomedical Research Centre, Baton Rouge, Louisiana, United States of America.
Emily
E
Mire
Division of Population Science, Pennington Biomedical Research Centre, Baton Rouge, Louisiana, United States of America.
Peter T
PT
Katzmarzyk
D061725:Accelerometry; D000328:Adult; D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose; D001794:Blood Pressure; D008076:Cholesterol, HDL / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D012307:Risk Factors; D057185:Sedentary Behavior; D014280:Triglycerides / Q000097:blood; D055105:Waist Circumference; D055815:Young Adult
D015415:Biomarkers; D001786:Blood Glucose; D008076:Cholesterol, HDL; D007328:Insulin; D014280:Triglycerides