Dietary Impact on Sleep, Rhythms and Related Physiology

Objective registration and analysis of sleep, based on polysomnography or validated wearable devices to capture macrosleep, spectral and microsleep features.

Continuous measurement of HRV, using a wearable device, focused on the metric Root Mean Square of the Successive Differences (RMSD); additional metrics (Standard Deviation of NN intervals (SDNN), low frequency to high frequency (LF/HF) ratio) analyzed for exploratory purposes.

Continuous measurement of heart rate using a wearable device

ECG-based heart rate measured at baseline, during stepping and repeatedly (up to 5 min) post-stair stepping, to assess recovery, also analyzed in relation to sleep metrics.

Morning, evening, and 24-h ambulatory measurement of systolic blood pressure, also analyzed in relation to sleep metrics.

Continuous (24-h) monitoring of interstitial glucose for analysis of mean levels and variability metrics (e.g., SD, coefficient of variation, postprandial changes), also analyzed in relation to sleep metrics.

Changes in levels of molecular factors such as DNA, hormones/proteins and metabolites, due to the preceding dietary intervention, and also in relation to sleep metrics.

Levels of CNS health biomarkers (such as brain-derived neurotrophic factor (BDNF), Tau (e.g. BD-tau) and Amyloid beta (Aβ) species, glial fibrillary acidic protein (GFAP), and Neurofilament light chain (NfL)).

Urine levels of excretion molecules (such as melatonin breakdown metabolites).

Change in metabolic fuel utilization as measured by respirometry, in response to the dietary interventions.

Changes in levels of fecal metabolites (such as short chain fatty acids, bile acids) due to each dietary intervention

Changes in fecal microbiota (metagenomic, compositional) due to each dietary intervention

Changes in levels of salival molecules (such as cortisol and melatonin), also in relation to sleep-circadian metrics.

Changes in salival microbiota (metagenomic, compositional) due to each dietary intervention

Glucometabolic response to a standardized 2-h glucose tolerance test, also analyzed in relation to sleep-circadian metrics.

Immune cell profile across the day in response to each diet

Change in self-reported sleep quality as assessed by the Pittsburgh Sleep Quality Index (PSQI), supplementing objective sleep data. Total Score (0-21; higher = worse).

Self-reported hunger and appetite across the day, and prior to and after meals, as assessed via visual analogue scales (VAS, i.e., with scores 0 for the lowest subjective rating, to 100 for the highest rating)

Body temperature measured via wearable sensors to assess effects of dietary interventions on thermoregulation and its relationship to sleep, circadian rhythms and metabolism.

Composite score from four tasks:

• Psychomotor Vigilance Task (PVT) - sustained attention; faster reaction times and fewer lapses corresponds to better performance;
• Go/No-Go Task - inhibitory control; higher accuracy on no-go trials and faster correct go responses corresponds to better performance;
• Task-Switching Task - cognitive flexibility; smaller switch cost (difference in reaction time between switch and repeat trials) and higher accuracy corresponds to better performance;
• Memorability Task - episodic memory; higher hit rate (0-100%) and fewer false alarms corresponds to better performance.

All scores will be standardized and averaged; higher composite values indicate better cognitive performance.

Self-reported assessment of mental wellbeing using validated subjective scales (visual analogue scales going from lowest 0 to highest of 100), to evaluate effects of diet and sleep.

Morning, evening, and 24-h ambulatory levels of central hemodynamics reflecting central blood pressure and arterial resistance, also analyzed in relation to sleep metrics

Exploratory subgroup analysis to determine if male vs. female participants differ in response to dietary interventions, for primary and secondary outcomes

Exploratory analysis to determine whether cardiorespiratory fitness parameters modulates responses to how the diets impact primary and secondary outcomes.

Dim Light Melatonin Onset as assessed via repeatedly measured melatonin levels, measured in the evening under standardized conditions

Analysis of levels of molecular biomarkers (such as CRP) in dried blood spots from finger samples, and how these correlate with biomarker levels from peripheral venous blood samples