Researchers identify blood metabolites linked to excessive daytime sleepiness; diet may offer protection

Scientists have identified seven blood metabolites associated with excessive daytime sleepiness (EDS), a common condition linked to higher risks of obesity, diabetes and cardiovascular disease, in a study that points to diet and hormones as influential factors.

Researchers at Brigham and Women's Hospital in Boston analyzed 877 naturally occurring small molecules in the blood of about 6,000 participants enrolled in the Hispanic Community Health Study and compared those measurements with responses to a questionnaire about how often people dozed off during the day. The team reported in eBioMedicine that seven metabolites showed significant associations with self‑reported daytime drowsiness.

Among the findings, higher levels of omega‑3 and omega‑6 fatty acids—nutrients commonly found in fatty fish, egg yolks and nuts—were associated with a lower likelihood of daytime sleepiness. Conversely, higher concentrations of tyramine, a compound found in fermented and overripe foods, were correlated with an increased risk of EDS and with indicators of poorer and delayed nocturnal sleep, particularly in men.

The researchers also identified three metabolites that showed sex‑specific differences. Hormones such as progesterone appeared tied to processes involved in sleep regulation, including melatonin production, the study said.

"Our study suggests diet and genetics may play an important role in EDS," said Dr. Tariq Faquih of Brigham and Women's Hospital. "As we learn what's happening biologically, we are beginning to understand why EDS occurs, the early signs that someone might have it, and what we can do to help patients. Conducting a clinical trial would be a big next step and could help us understand if omega‑3s and omega‑6s obtained from diet could help lower risk of EDS."

Excessive daytime sleepiness affects a substantial portion of adults in the United States; prior estimates have suggested the condition may affect up to one‑third of adults. EDS is associated with impaired daytime functioning and with longer‑term health risks including metabolic disorders and cardiovascular disease.

The investigators cautioned that the study has limitations. Sleepiness and sleep quality were assessed using a questionnaire rather than objective laboratory tests such as polysomnography, which could introduce reporting biases or confounding. The researchers also noted challenges in precisely quantifying the biologically active levels of metabolites in the body and said observational associations do not prove causation.

Because the analysis was cross‑sectional, the team could not determine whether the metabolite differences cause sleepiness, result from it, or are linked through other factors. The authors recommended follow‑up clinical trials to test whether dietary changes or supplementation with omega fatty acids could reduce the risk or severity of EDS.

The new findings add to a growing body of research examining how diet and lipids influence brain health and sleep. A separate study by researchers at King's College London and Queen Mary University of London recently reported that women with Alzheimer's disease had lower levels of certain unsaturated fatty acids in their blood, a result that investigators said could help explain sex differences in neurodegenerative risk and point to lifestyle interventions.

The study in eBioMedicine underscores interest in metabolomics—large‑scale measurement of small molecules in blood—as a tool to uncover biological pathways underlying common complaints such as daytime sleepiness. Researchers and clinicians said further work, including randomized trials and studies using objective sleep measures, will be needed to translate these molecular associations into diagnostic tests or treatment recommendations.