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Sedentary Behavior and Cardiovascular Risk: How Much Sitting is Too Much?

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  Dr. Madhur Verma, Associate Professor, Dept. of Community & Family Medicine, AIIMS, Bathinda, Punjab; Dr Sanjay Kalra, DM (AIIMS); Imm. Past President SAFES, Bharti Hospital, Karnal, Haryana, India    19 November 2024

Spending more than 10.5 hours daily in sedentary behavior significantly raises the risk of future heart failure (HF) and cardiovascular (CV) death, even among people who adhere to the recommended physical activity guidelines of ≥150 minutes per week, says a study published in the Journal of the American College of Cardiology.1,2

 

This study investigated the relationship between accelerometer-measured (worn on the wrist for seven days) sedentary time and the risk of specific cardiovascular (CV) outcomes such as incident atrial fibrillation (AF), myocardial infarction (MI), HF, and CV-related mortality in participants of the UK Biobank prospective cohort. To examine the potential modifying effect of moderate-to-vigorous physical activity (MVPA), analyses were adjusted for MVPA levels and stratified based on adherence to the guideline-recommended threshold of ≥150 minutes per week.

 

Among the 89,530 study participants of the UK biobank included in the present study, the average age was 62 and 56.4% were women. The median daily sedentary time was 9.4 hours. After an average follow-up of eight years, ~5% developed incident AF, 2.1% developed incident HF, 1.84% developed indecent MI and 0.94% died of CV causes.

 

After adjusting for demographic and lifestyle factors, sedentary time exceeding 10.6 hours per day (top quartile) was associated with significantly higher risks of HF with hazard ratio (HR) of 1.45 as well as CV mortality with HR 1.62 compared to the reference group with 8.2 - 9.4 hours per day of sedentary time (second tertile). Greater sedentary time was also linked to increased risks of incident AF (HR 1.11) and MI (HR 1.15), with a nearly linear relationship observed. Notably, the associations between sedentary behavior and risks of HF and CV mortality remained significant even among individuals meeting the guideline-recommended levels of MVPA.

 

Among individuals with >10.6 hours/day of sedentary time, replacing sedentary behavior with other activities significantly reduced the excess CV risk associated with prolonged sedentary time. A 30-minute reduction in sedentary time was associated with a lower risk of HF (HR 0.93). This benefit was observed even among those meeting the guideline-recommended levels of moderate-to-vigorous physical activity (HR 0.93).

 

This study reaffirms the link between sedentary behavior and cardiovascular health. The impact of sedentary time varied depending on the cardiovascular outcome as shown in this study. Specifically, for AF and MI, the risk increased progressively over time without notable shifts. However, for HF and CV-related mortality, the risk remained low until sedentary time exceeded approximately 10.6 hours per day, at which point it rose sharply.

 

These findings specify a critical threshold at 10.6 hours/day, beyond which the risk of adverse outcomes substantially increases. The authors note that wrist-worn accelerometers may inaccurately classify standing time as sedentary due to limitations in detecting posture. Extending the monitoring period could improve data accuracy on activity habits and patterns. Nevertheless, minimizing sedentary behavior is crucial for reducing cardiovascular disease (CVD) risk, even for physically active individuals. “Although guideline-adherent MVPA partially mitigates excess risk, optimizing sedentary behavior appears to be important even among physically active individuals”, concluded the authors.

 

References

 

1.   Ajufo E, et al. Accelerometer-measured sedentary behavior and risk of future cardiovascular disease. J Am Coll Cardiol. 2024 Nov 11:S0735-1097(24)09920-0. doi: 10.1016/j.jacc.2024.10.065.

2.   ACC Press release. Available at: https://www.acc.org/About-ACC/Press-Releases/2024/11/15/16/33/Sitting-Too-Long-Can-Harm-Heart-Health-Even-for-Active-People. Dated Nov. 15, 2024. Accessed on Nov. 17, 2024.

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