Cerebromicrovascular Effects of Time-Restricted Eating in Older Adults

Functional near infrared spectroscopy (fNIRS) will be performed during the cognitive n-back task. fNIRS approach generates data that represent a relative change in oxygenated hemoglobin measured over the cortical brain tissues. fNIRS data is analyzed using a pipeline based on the General Linear Model (GLM) approach created using the Brain AnalyzIR toolbox and implemented in MatLab. At the subject level, regression coefficients (beta values) are extracted to characterize individual neurovascular coupling response in the prefrontal cortex across all n-back blocks. It is expected that more difficult cognitive tasks will lead to increased neurovascular coupling responses in healthy individuals, but no clinically relevant ranges exist for this measure.

Flicker light-induced dilation of the retinal vessels (percentage increase over baseline diameter) will be measured in the right or left eye of each study participant using the Dynamic Vessel Analyzer (DVA, IMEDOS Systems, Jena, Germany). The change in retinal vessel diameters is tracked and reported as a %change from baseline, before and after treatment.

Transcranial Doppler sonography will be used to measure the change in the blood flow velocities during the cognitive n-back task between before and after treatment.

Changes in microvascular endothelial function will be assessed using laser speckle contrast imaging (LSCI) in the hand using the flow mediated dilation approach. The change in skin perfusion is calculated and reported as a fold change from baseline.

Changes in macrovascular endothelial function will be assessed using sonography during flow mediated dilation approach. The change in brachial artery diameter is calculated and reported as a %change from baseline.

Transcutaneous deep tissue oxygen saturation will be measured using the inSpectra near infrared device. The data are calculated and reported as a %change from baseline.

The arterial stiffness will be measured using the pulse wave analysis approach (SphygmoCor, Atcor medical, Itasca IL, or similar). Analysis generated the augmentation index which will be used for comparison before and after treatment.

ECG will be recorded for heart rate variability analysis. The values of high frequency domain, low frequency domain, their ratio, as well as total power will be calculated and used for comparison before and after treatment.

Video recordings of the sublingual vasculature will be performed using the high definition video camera GlycoCheck (Microvascular health solutions). Data collected will include perfused boundary region (um), and will be used for comparison before and after treatment.

Video recordings of the sublingual vasculature will be performed using the high definition video camera GlycoCheck (Microvascular health solutions). Data collected will include capillary density (mm/mm^2), and will be used for comparison before and after treatment.

Video recordings of the sublingual vasculature will be performed using the high definition video camera GlycoCheck (Microvascular health solutions). Data collected will include red blood cell velocity (um/sec), and will be used for comparison before and after treatment.

Flanker Inhibitory Control and Attention Test was used to assess inhibitory control and attention. The participant is asked to focus on a particular stimulus while inhibiting attention to the stimuli flanking it. Scores are fully adjusted to nationally representative normative sample of NIH toolbox test takers, accounting for age, sex, race, and education (mean = 50; SD = 10). Higher scores represent better outcomes.

Picture Sequence Memory Test was used to assess episodic memory. Participants are shown a number of activities, and then asked to reproduce the sequence of pictures as it was presented to them. Scores are fully adjusted to nationally representative normative sample of NIH toolbox test takers, accounting for age, sex, race, and education (mean = 50; SD = 10). Higher scores represent better outcomes.

List Sorting Working Memory Test was used to assess working memory. The participant is asked to recall and sequence different stimuli that are presented visually and via audio. Scores are fully adjusted to nationally representative normative sample of NIH toolbox test takers, accounting for age, sex, race, and education (mean = 50; SD = 10). Higher scores represent better outcomes.

Picture Vocabulary Test measures receptive vocabulary administered in a computer-adaptive test (CAT) format. Respondents select the picture that most closely matches the meaning of the word. Scores are fully adjusted to nationally representative normative sample of NIH toolbox test takers, accounting for age, sex, race, and education (mean = 50; SD = 10). Higher scores represent better outcomes.

Dimensional Change Card Sort Test was used to assess cognitive flexibility and attention. The participant is asked to match a series of picture pairs to a target picture. Scores are fully adjusted to nationally representative normative sample of NIH toolbox test takers, accounting for age, sex, race, and education (mean = 50; SD = 10). Higher scores represent better outcomes.

Pattern Comparison Processing Speed Test was used to assess processing speed. Participants are asked to quickly determine whether two stimuli are the same or not the same. Scores are fully adjusted to nationally representative normative sample of NIH toolbox test takers, accounting for age, sex, race, and education (mean = 50; SD = 10). Higher scores represent better outcomes.