FIU-RCMI Research Project #2 Project Summary Emerging evidence suggests a bidirectional relationship between sleep disturbance and alterations in the gut microbiome. This study aims to examine the effect of sleep health and dysfunction in influencing cognition while accounting for the role of the gut microbiome in a community-based Latinx sample. Despite its importance, studies exploring the effect of sleep on the gut microbiome, and the subsequent effect on the cognition of humans are extremely limited. Of the preliminary investigations that do exist, none have been conducted with Latinx community-living samples. While Latinx samples were the focus of two gut microbiome studies, which provided preliminary evidence for the unique gut microbiome of this population, our proposed study is innovative in that it includes cognitive measures, cortisol sampling, and objective measures of sleep. Guided by the National Institutes of Minority Health and Health Disparities Framework, we will also explore sociocultural factors at various levels of influence that may impact sleep, cognition, and the gut microbiome. There is an urgent need for studies of this kind given that the gut microbiome may have a direct effect on cognition and sleep, positioning it as a modifiable risk factor for cognitive decline. Sleep disturbance, a modifiable risk factor for cognitive decline, including Alzheimer's disease, is bidirectionally-related to the gut microbiome, variations in sleep patterns affect the structure and diversity of the gut microbiome, and the gut microbiome is influential in circadian cycles and hormones related to sleep and waking. Investigations examining the microbiota-gut-brain axis are essential in community-based samples to identify modifiable risk factors for cognitive decline and inform novel interventions. We will recruit 150 Latinx midlife adults through staggered recruitment and leveraging our existing resources: for a total of 450 observations. Each participant will be administered a battery of neurocognitive and sleep assessments and will provide objective sleep data through a wrist-worn actigraphy device, 3 saliva samples in one day to assess salivary cortisol, and a stool sample to examine the gut microbiome through whole-genome shotgun sequencing. Using this data, we will examine four aims: Aim 1. Using integrated microbiome analyses, we will examine correlations between gut microbiome profiles, and measures of cognition. Aim 2. We will examine the bivariate relationship between sleep and gut microbiome profiles. Aim 3a: We will examine the relation between sleep and measures of cognition. Aim 3b: We will examine the interconnections between gut microbiome profiles, measures of cognition, and sleep using two mediation models. Aim 4: We will examine the interrelations between gut microbiome profiles, stress (salivary cortisol), measures of cognition, and sleep. Using an integrated analysis of the gut microbiome, cognition, stress through saliv...