A standardised saffron extract improves subjective and objective sleep quality in healthy older adults with sleep complaints: results from the Gut-Sleep-Brain Axis randomised, double-blind, placebo-controlled pilot study

Abstract

Sleep disorders may increase neurodegenerative diseases risks and alter gut microbiota composition. Saffron (Crocus sativus) supplementation has been linked to sleep improvements and gut microbiome changes, but its effect on sleep quality through gut microbiota-brain axis modulation remains unexplored. A randomised, placebo-controlled pilot study of saffron (30mg/day for 4-weeks) was conducted with 52 older adults (55-85 years) experiencing sleep complaints. Subjective and objective sleep quality were measured using validated questionnaires and electroencephalography-based sleep tracker respectively. A subgroup (n=26) underwent microbiome analysis. Saffron supplementation improved subjective sleep quality (p=0.02) and sleep efficiency (p=0.04). Objective measures showed reduced latency to persistent sleep (p=0.003) and sleep onset latency (p=0.03). Linear discriminant analysis effect size analysis of the microbiome revealed increases in Faecalibacterium (q=0.013), Lachnoclostridium (q=0.045), Prevotella (q=0.022), UBA1819 (q=0.020) and Oscillibacter (q=0.045), while decreasing Dialister (q=0.028). Univariate analysis further indicated increases in Lachnospiraceae-UGC-001 (p=0.020) and Roseburia (p=0.03), with a decrease in Turicibacter (p=0.045) in the saffron group. Oscillibacter and UBA1819 correlated with subjective measures of sleep efficiency (r=0.63, p=0.0007) and sleep latency (r=-0.39, p=0.04. Changes in Dialister, Turicibacter and UBA1819 were correlated with several measures of objective sleep quality including wake duration, latency to persistent sleep and wake-after-sleep-onset. Four-weeks saffron supplementation improved both subjective and objective sleep quality in older adults with sleep complaints, while increasing gut bacteria that produce short-chain fatty acids. These results pave the way for further randomised controlled trials exploring the links between sleep quality and gut health and may help devising new preventative strategies for age-related brain disorders.