The Effect of Prolonged Sitting and Sitting Interruption on Cerebral Hemodynamics

Introduction: Sedentary behavior (SB) is associated with an increased risk of Alzheimer’s Disease and Related Dementias. Increased cerebral arterial stiffening (AS) during acute bouts of SB could be a factor explaining this association. However, there is limited understanding of how acute SB affects cerebral AS, and whether interrupting SB can reduce cerebral AS. Studies & Methods: Data from 22 sedentary (>8 hours sitting daily), physically inactive (<150 min/week moderate-vigorous physical activity), middle aged (30-60 years old) adults was analyzed from an ongoing trial. Participants underwent four, 4-hour sitting conditions: 1) uninterrupted sitting, 2) once/hour 15-minute standing breaks, 3) once/hour 5-minute walking breaks, 4) both 15-minute standing and 3 of sitting with scheduled interruption (standing breaks, walking breaks, and both hourly). AS data measured using heart-to-middle cerebral pulse wave velocity (hmPWV) from these participants was used for Study 1 (reliability of hmPWV) and Study 2 (using hmPWV to evaluate changes during sitting) of the proposed dissertation. For Study 3, trial participants and a supplemental participant pool were recruited to conduct focus groups related to SB and SB interruption. Results: The Aim 1 study found the reliability of hmPWV measured using electrocardiogram (ECG) and impedance cardiogram (ICG) to be moderate (ICC = 0.632 with ECG, ICC = 0.523 with ICG) but both were below our acceptability criteria (ICC = 0.700). The Aim 2 study found a large effect of time for hmPWV (b = 0.979 m/s, d = 2.56, p < 0.001) irrespective of condition. Lastly, insights from our focus groups indicated that sedentary but physically active adults likely have lower barriers to sedentary behavior interruption than physically inactive, sedentary adults. Conclusions: While promising, additional work should be performed to standardize hmPWV measures to improve reliability. More intense and frequent SB interruption strategies can be trialed for effectiveness. Translating SB interruption strategies trialed in samples of sedentary, physically inactive adults can likely be easily translated to sedentary but physically active adults due to lower perceived barriers to behavior change in this realm.