Reconsidering the sedentary behaviour paradigm

Abstract

Aims: 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).

Conclusion: 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.

Figure 1. Associations between total sedentary time and cardio-metabolic biomarkers, corrected for two different measures of physical activity (MVPA minutes, and total physical activity) in adults in the 2003/04 and 2005/06 U.S.

National Health and Nutrition Examination Survey. Only biomarkers where significant associations were observed are shown. MVPA =  moderate to vigorous physical activity; HDL =  High-density lipoprotein; HOMA %B =  Homeostasis Model Assessment steady state beta cell function, HOMA %S =  Homeostasis Model Assessment insulin sensitivity, OGTT =  oral glucose tolerance test.