Prolonged sitting may negatively impact vascular health

Introduction and methods

Existing data suggest that prolonged sitting has a negative effect on peripheral vasodilatory function, but it is not clear whether it impacts central vascular health and peripheral vasoconstriction [1-4]. This study assessed whether a single session of prolonged, uninterrupted sitting (3 hours) affects markers of both peripheral (i.e., vasodilatory and vasoconstrictor function) and central vascular health (i.e., aortic: pressures, wave reflection, and vascular stiffness).

For this purpose, 20 asymptomatic non-smoker volunteers, aged 18-55 years, without cardiovascular (CV), metabolic or neurological diseases were recruited, and asked to remain seated for 3 hours. Before, during and after the sitting period, the following measurement were done:

• mean arterial pressure (MAP) and resting heart rate (HR)
• augmentation pressure (AP), defined as the maximum systolic pressure minus the pressure at the inflection point, and augmentation index (Aix; AP expressed as a percentage of total pulse pressure)
• forward (Pf) and backward (Pb) components of the aortic pressure waveform
• reflection magnitude (RM%) of arterial wave reflection
• aortic pulse wave velocity (aPWV)
• flow-mediated dilation (FMD) of the distal posterior tibial artery and total hyperemic blood velocity (AUC) response during FMD

Effect sizes were calculated pairwise and reported using Cohen’s d, with <0.20 considered a small, >0.20 to <0.50 a moderate, and >0.60 a large effect.

Main results

When comparing measurements before and after sitting time, there was:

Central CV hemodynamic response

• no change in MAP (P>0.05)
• a significant decrease in resting HR (pre sit=65±2 vs. post sit=60±2; P<0.001; d=0.56), AP (pre sit=5±1 vs. post sit=1±1; P<0.001; d=0.69), and AIx (pre sit=13±3 vs. post sit=3±1 %; P<0.001; d=0.71)
• no significant change for Pf (pre sit=30±1 vs. post sit=29±1; P=0.62; d=0.19)
• no significant change in Pb (pre sit=15±1 vs. post sit=13±1; P=0.19; d=0.4) and RM% (pre sit=50±2 vs. post sit=47±2; P=0.13; d=0.3) a moderate, statistically significant increase in aPWV (pre sit=5.7±1 vs. post sit=6.1±1.1 m/s; P=0.009; d=0.36), which was only seen in men in secondary sensitivity analysis.

Peripheral vascular response

• a significant decrease in FMD (pre sit=0.5±0.04 vs. post sit=0.3±0.04 mm; P=0.014, d=0.29)
• a non-significant trend for a reduction in resting arterial tone (pre sit=61±7 vs. post sit=46±8; P=0.083, d=0.2) and the FMD stimulus (Shear AUC-40: pre sit=20695±2123 vs. post sit=15533±1830; P=0.073, d=0.21)
• a significant decrease in total hyperemic blood velocity (AUC) (pre sit=2196±333 vs. post sit=1157±172; P=0.003; d=0.31)

Conclusion

Several measurements in a small sample of healthy individuals suggest that prolonged sitting has a negative impact on peripheral and central vascular health, signified primarily by a reduced leg vasodilatory function and an increase in aortic vascular stiffening These data suggest that a single bout of prolonged, uninterrupted sitting may serve as a precursor for initiating the deleterious CV health response associated with long-term sedentarism.

References

Find this article online at Am J Cardiol