Sleep Medicine

Probiotics and synbiotics modestly improve perceived sleep in exercised populations.

A SWiM of six RCTs (n = 180) in athletes found supplementation improved subjective sleep quality and sometimes sleep latency. Nine of twelve primary sleep outcomes favored probiotics or synbiotics, with significant pooled signals for both interventions. Interventions lasted 4–17 weeks across multiple sports and continents, suggesting generalizability to training populations. Evidence supports cautious adjunctive use for athletes, but larger standardized trials are needed before routine recommendation. 1

Sleep extension reduced serum BDNF in adolescents with severe obesity.

In a randomized crossover study (n = 36), increasing time in bed by ~1.5 hours nightly lowered serum BDNF by about 14% versus habitual sleep. Sleep restriction did not change BDNF compared with habitual sleep, suggesting a direction-specific effect. Authors hypothesize lower BDNF after extension reflects reduced physiological stress or compensatory neurotrophic signaling. Clinically, consider that experimental sleep extension alters neurotrophic markers; metabolic and mechanistic implications remain uncertain. 2

Transcutaneous vagus nerve stimulation improves sleep quality and insomnia severity.

Meta-analysis of 13 RCTs found tVNS improved PSQI scores and reduced insomnia severity versus control. Effects were stronger when stimulation targeted the concha region and in younger participants. Trials used varied tVNS protocols, so optimal parameters and durability of benefit remain unclear. tVNS is a reasonable adjunctive option for adults with insomnia, pending standardization and longer-term outcome data. 3