Objective: Because of inconsistent findings regarding the relationship between sleep quality and cognitive function in people with age-related memory complaints, we examined how self-reports of sleep quality were related to multiple domains of both objective and subjective cognitive function in middle-aged and older adults. Design: A cross-sectional study involving analysis of baseline data, collected as part of a clinical trial. Measurements: Two hundred and three participants (mean age = 60.4 [6.5] years, 69.0% female) with mild memory complaints were asked to rate their sleep quality using the Pittsburgh Sleep Quality Index (PSQI) and their memory performance using the Memory Functioning Questionnaire (MFQ), which measures self-awareness of memory ability. Neurocognitive performance was evaluated using the Continuous Performance Test (CPT), Trail Making Test, Buschke Selective Reminding Test, and the Brief Visuospatial Test – Revised (BVMT-R). Results: Total PSQI scores were significantly associated with objective measures of sustained attention (CPT hit reaction time by block and standard error by block) and subjective memory loss (MFQ frequency and seriousness of forgetting). The PSQI components of (poorer) sleep quality and (greater) sleep disturbance were related to (worse) sustained attention scores while increased sleep latency and daytime sleepiness were associated with greater frequency and seriousness of forgetting. Conclusions: Sleep quality is related to both objective measures of sustained attention and self-awareness of memory decline. These findings suggest that interventions for improving sleep quality may contribute not only to improving the ability to focus on a particular task but also in reducing memory complaints in middle-aged and older adults.

Background We showed that pomegranate juice (PomJ) may help to maintain memory in adults older than 50 years of age. The mechanism for this effect is unknown, but may involve tryptophan (Trp) and its metabolites, which are important in brain function. Objectives We aim to test the hypothesis that PomJ and its metabolites ellagic acid (EA) and urolithin A (UA) affect Trp metabolism. Methods Stool and plasma from a cohort (11 PomJ, 9 placebo) of subjects enrolled in our double-blind, placebo-controlled trial (NCT02093130) were collected at baseline and after 1 year of PomJ or placebo drink (PL) consumption. In mice, cecum and serum were collected from DBA2J mice receiving 8-weeks’ dietary 0.1% EA or UA supplementation. Trp metabolites and intestinal microbiota were analyzed by liquid chromatography–mass spectrometry and 16S rRNA gene sequencing respectively. Results In the human study, the change in plasma Trp metabolite indole propionate (IPA) over one year was significantly different between PomJ and PL groups (P = 0.03). In serum of experimental mice, we observed 230% increase of IPA by EA but not UA, 54% increase of IS by UA but not EA, and 43% and 34% decrease of kynurenine (KYN) by EA and UA respectively. In cecum, there were 32% decrease of Trp by UA but not EA and 86% decrease of KYN by EA but not UA (P < 0.05). The abundance of two genera Shigella and Catenibacterium was reduced by PomJ in humans as well as by UA in mice and their abundance was negatively associated with blood IPA in humans and mice (P < 0.05). Conclusion These results suggest a novel mechanism involving the regulation of host and microbial Trp metabolism that may contribute to the health benefits of ellagitannins and EA enriched food, such as PomJ.