Sleep

1. Sleepwell supported · human dataAdded 8 August 2026

   Bottling up emotions tracks with worse sleep, but the link is small

   Pooling 23 independent samples of healthy adults (N = 13,636), habitual expressive suppression, routinely masking outward emotion, showed a small but consistent association with poorer self-reported sleep quality (r =.14), and the link was stronger in studies focused on COVID-19-related stress.

   ⚠What it shows: A meta-analysis of 23 samples totalling 13,636 non-clinical adults, but built on zero-order correlations from self-report questionnaires, so it shows association only: suppression could follow poor sleep as easily as precede it, and the effect is small.Meta-analysis · BMC Psychol

   Full breakdown →Cultural background and pandemic context as moderators of the association between expressive suppression and sleep quality in healthy adults: a systematic review and meta‑analysis. BMC Psychol 2026
2. Sleepwell supported · human dataAdded 8 August 2026

   Tai chi and Qigong ease sleep troubles in older adults

   A meta-analysis of 13 randomised controlled trials found community-based traditional Chinese exercises such as tai chi and Qigong reduce sleep disturbance in community-dwelling older adults; Qigong's effect was slightly larger but not significantly different from tai chi's.

   ⚠What it shows: Meta-analysis of 13 RCTs in community-dwelling older adults; the abstract reports no pooled effect sizes, the Qigong-versus-tai-chi difference was not significant, and applicability to younger people is untested.Meta-analysis · J Transcult Nurs

   Full breakdown →Sleep Calculator →Beneficial Effects of Community-Based Traditional Chinese Exercises on Sleep Disturbance Among Older Adults: Systematic Review, Meta-Analysis, and Meta-Regression of Randomized Controlled Trials. J Transcult Nurs 2026
3. Sleepwell supported · human dataAdded 8 August 2026

   App-based insomnia therapy works, and lifts mood too

   Digitally delivered cognitive behavioural therapy for insomnia reduced both insomnia and depression severity in a meta-analysis of seven randomised trials totalling 3,597 adults, with effects comparable to face-to-face CBT-I and generally maintained at follow-ups of 6 weeks to 6 months.

   ⚠What it shows: Meta-analysis of only seven RCTs; follow-up limited to 6 weeks to 6 months, and effects on depression were smaller than on insomnia.Meta-analysis · PeerJ

   Full breakdown →Sleep Calculator →The efficacy of digital cognitive behavioral therapy for insomnia and depression: a systematic review and meta-analysis of randomized controlled trials. PeerJ 2023
4. Sleeppreliminary · human dataAdded 8 August 2026

   Clearing the sinuses tracked with quieter, steadier breathing at night

   Across 15 studies, treating rhinosinusitis medically or surgically was frequently followed by reductions in the apnoea-hypopnoea index and improvements in endoscopic findings, sleep quality and daytime sleepiness, although subjective nasal symptom outcomes varied between studies.

   ⚠What it shows: Systematic review of 15 mostly before-and-after studies with treatments ranging from sinus surgery to biologics; heterogeneity was too great for any pooled estimate, so no effect size exists and uncontrolled designs cannot establish cause.Systematic review · Medicina (Kaunas)

   Full breakdown →The Impact of Rhinosinusitis and Its Treatment on Sleep-Disordered Breathing: A Systematic Review. Medicina (Kaunas) 2026
5. Sleeppreliminary · human dataAdded 6 August 2026

   Exercise may lift students' sleep quality, with caveats

   Structured exercise programmes reduced university students' Pittsburgh Sleep Quality Index scores by 2.43 points versus non-exercise controls in a meta-analysis of seven trials with 701 participants, but very low evidence certainty and heavy variation between studies temper the finding.

   ⚠What it shows: Meta-analysis of only 7 RCTs (701 university students) with very high heterogeneity (I²=91.7%); the 95% prediction interval crossed zero and GRADE certainty was very low to low, so the effect may not generalise.Meta-analysis · Front Public Health

   Full breakdown →Pittsburgh Sleep Quality Index (PSQI) explained →Sleep Calculator →Exercise interventions to improve sleep quality in university students: a systematic review and meta-analysis of randomized controlled trials. Front Public Health 2026
6. Sleepwell supported · human dataAdded 6 August 2026

   A warm soak added sleep time, not better sleep scores

   A meta-analysis of ten randomised trials in healthy adults found warm-water immersion thermotherapy increased total sleep time (SMD 0.63) and sleep efficiency (SMD 0.64), but did not significantly change sleep latency or any Pittsburgh Sleep Quality Index score.

   ⚠What it shows: Meta-analysis of ten RCTs in healthy adults; both significant effects were borderline, water temperature, timing and immersion protocols differed between trials, and subjective sleep quality did not improve on any PSQI component.Meta-analysis · Int J Biometeorol

   Full breakdown →Sauna Therapy →Sleep Calculator →The effect of water immersion thermotherapy on sleep quality: a systematic review and meta-analysis of randomized controlled trials. Int J Biometeorol 2026
7. Sleepwell supported · human dataAdded 6 August 2026

   An afternoon nap can boost athletes' endurance

   A meta-analysis of 12 randomised trials in 179 team-sport athletes found early-afternoon napping produced a large improvement in endurance and a moderate gain in agility versus no nap, with naps longer than 60 minutes showing the biggest effects.

   ⚠What it shows: Meta-analysis of 12 RCTs but only 179 athletes in total; findings apply after presumed normal night sleep, and effects on cognitive and technical performance remain uncertain.Systematic review · Front Physiol

   Full breakdown →Sleep Calculator →The effect of daytime napping on the athletic performance of team ball sports athletes: systematic review and meta-analysis. Front Physiol 2026
8. Sleeppreliminary · human dataAdded 6 August 2026

   Exercise may help shift workers sleep, evidence thin

   A systematic review of ten randomised trials in 420 shift workers found that eight reported significant improvements in sleep measures such as PSQI score, total sleep time, sleep efficiency or wake after sleep onset following structured exercise, and three reported better alertness, reaction time or short-term memory. Effect sizes were inconsistent and 80% of the trials had some concerns or high risk of bias.

   ⚠What it shows: Narrative systematic review of ten small RCTs, 420 adult shift workers (60% in healthcare); interventions and outcome measures were too heterogeneous to pool, 80% of trials had bias concerns, and adherence was hampered by fatigue and irregular schedules.Systematic review · Front Public Health

   Full breakdown →Sleep Calculator →Exercise interventions for sleep and cognitive dysfunction in shift workers: a systematic review of randomized trials. Front Public Health 2026
9. Sleepwell supported · human dataAdded 6 August 2026

   Tai chi lifted older adults' sleep at 150 min a week

   In a meta-analysis of nine randomised controlled trials in 1,166 older adults, tai chi reduced Pittsburgh Sleep Quality Index scores by an average of 1.53 points; weekly totals of 150-300 min produced a significant improvement, while less than 150 min did not.

   ⚠What it shows: Meta-analysis of nine RCTs (1,166 older participants) using self-reported sleep questionnaires, with high statistical heterogeneity (I2 = 78%) and no possibility of blinding participants to an exercise they are doing; the dose findings come from subgroup comparisons, not from trials designed to test dose.Meta-analysis · Eur Geriatr Med

   Full breakdown →Pittsburgh Sleep Quality Index (PSQI) explained →Sleep Calculator →At least 150 min per week of Tai chi practice improves sleep quality in the older people: evidence from a meta-analysis. Eur Geriatr Med 2025
10. Sleeppreliminary · human dataAdded 6 August 2026

    Shift-work sleep fixes rest on thin evidence

    A Cochrane review of 17 randomised trials in shift workers (556 relevant participants) could not determine whether bright light, napping or other non-drug measures reduce sleepiness at work or improve sleep between shifts. Pooled bright light at night cut sleepiness by 0.83 points on one scale, but that estimate rests on very low quality evidence.

    ⚠What it shows: Cochrane systematic review of 17 small RCTs totalling 556 participants; studies were too heterogeneous to pool in most cases and the evidence was rated low to very low quality, with only one comparison at moderate quality. Databases were searched to August 2015, so more recent trials are not included. Inconclusive is not the same as ineffective.Meta-analysis · Cochrane Database Syst Rev

    Full breakdown →Optimising Your Sleep Environment →Person-directed, non-pharmacological interventions for sleepiness at work and sleep disturbances caused by shift work. Cochrane Database Syst Rev 2016
11. Sleepwell supported · human dataAdded 6 August 2026

    Throat exercises may ease sleep apnoea; lifting doesn't

    A meta-analysis of 13 randomised trials found oropharyngeal (mouth-and-throat) muscle training and respiratory muscle training were associated with reductions in obstructive sleep apnoea severity, while conventional resistance training was not. Daytime sleepiness showed no consistent, clinically meaningful improvement with any modality.

    ⚠What it shows: Meta-analysis of 13 small RCTs totalling 429 participants; substantial heterogeneity in protocols, durations and participants, and daytime sleepiness did not consistently improve.Meta-analysis · Respir Med

    Full breakdown →Meta-analysis explained →Sleep Calculator →Efficacy of therapies based on muscle strength training among individual with obstructive sleep apnea - a systematic review and meta-analysis. Respir Med 2026
12. Sleeppreliminary · human dataAdded 6 August 2026

    Fenugreek linked to better postpartum sleep scores

    In a triple-blind trial of 60 first-time mothers, a daily 700 mg fenugreek seed extract capsule taken from the first postpartum week until day 60 was associated with better self-reported sleep quality than placebo at days 30 and 60. The two groups' sleep scores already differed significantly before treatment started, so the analysis had to be adjusted for that gap.

    ⚠What it shows: One small trial, n=60 first-time mothers attending health centres in Sabzevar, Iran; the groups differed significantly on sleep scores at baseline (p=0.009), sleep was measured only by self-report questionnaire, and the authors themselves call for objective sleep measurement.Study · Matern Health Neonatol Perinatol

    Full breakdown →Fenugreek guide →Sleep Calculator →The effect of fenugreek oral capsule on the sleep quality of primiparous women in the postpartum period: a triple‑blind randomized controlled trial. Matern Health Neonatol Perinatol 2026
13. Sleeppreliminary · human dataAdded 6 August 2026

    Sleep advice shifted habits, not measured sleep

    In a three-arm randomised trial of 66 regional and national track and field athletes, written and verbal sleep hygiene advice both significantly improved Sleep Hygiene Index scores compared with a control group, but ten days of actigraphy showed no significant change in objective sleep parameters. The only hint of benefit was a non-significant increase in total sleep time driven by earlier bedtimes.

    ⚠What it shows: One RCT in 66 track and field athletes over a ten-day intervention; the only significant improvement was a self-reported questionnaire score, six objective actigraphy measures did not shift, and the total sleep time trend was not statistically significant.Study · J Sports Med Phys Fitness

    Full breakdown →Optimising Your Sleep Environment →Sleep Calculator →Written vs. verbal sleep hygiene strategies administration in track and field athletes: a randomized controlled trial study. J Sports Med Phys Fitness 2026
14. Sleeppreliminary · human dataAdded 30 July 2026

    Sleep diaries alone matched online sleep coaching

    In a randomised trial of German shift workers, four personalised online counselling messages did not improve sleep efficiency any more than simply completing weekly sleep diaries. Sleep efficiency, insomnia and depression symptoms improved in both groups, while daytime sleepiness improved in neither.

    ⚠What it shows: One small superiority RCT, intention-to-treat n=66 German shift workers, four weeks, waiting-list control that also kept sleep diaries; self-reported outcomes and the authors flag limited sample size and time frame.RCT · Sci Rep

    Full breakdown →Sleep Calculator →Efficacy of an anonymous, preventive, personalized online counselling to improve shift workers' sleep quality: a randomized controlled trial. Sci Rep 2026
15. Sleeppreliminary · human dataAdded 30 July 2026

    Snoring, not insomnia, linked to pregnancy hypertension

    In a meta-analysis of 19 cohort studies covering 9,460,018 pregnancies, sleep-disordered breathing was associated with higher odds of gestational hypertension (OR 1.50) and preeclampsia (OR 1.83), with obstructive sleep apnoea the strongest signal (preeclampsia OR 2.13). Insomnia and poor sleep quality on the Pittsburgh Sleep Quality Index were not significantly associated with hypertensive outcomes.

    ⚠What it shows: Meta-analysis of 19 observational cohort studies, so associations only and open to confounding by factors such as body weight; sleep disorders were defined and measured differently across studies and no trial has shown that treating them lowers hypertensive risk.Study · Eur J Obstet Gynecol Reprod Biol

    Full breakdown →Blood pressure explained →Association between sleep disorders during pregnancy and hypertensive disorders of pregnancy: A systematic review and meta-analysis of cohort studies. Eur J Obstet Gynecol Reprod Biol 2026
16. Sleeppreliminary · human dataAdded 30 July 2026

    Hydrogen jelly did not improve sleep overall

    In a randomised, double-blind trial of 44 healthy adults with poor sleep, hydrogen-rich jelly was no better than placebo on any sleep or anxiety measure. Only in exploratory analysis did people with fewer hydrogen-producing gut bacteria report greater improvement in sleep quality and mental stress.

    ⚠What it shows: One small randomised, double-blind, placebo-controlled trial in 44 healthy adults with poor sleep quality; the overall result was null and the microbiome finding is an exploratory subgroup interaction the authors themselves call a hypothesis needing confirmation in larger studies.RCT · Sci Rep

    Full breakdown →Gut microbiome explained →Individual variability in hydrogen-producing microbes influences the response to hydrogen supplementation on sleep quality: a randomized, double-blind, placebo-controlled, parallel study. Sci Rep 2026
17. Sleeppreliminary · human dataAdded 29 July 2026

    Sleep apnoea and depression often travel together

    Depression and bipolar disorder frequently co-occur with obstructive sleep apnoea, a large pooled analysis of 23 studies finds, with older age and body-mass index significantly shaping how common the overlap is. The authors argue this supports systematic screening for one condition when the other is present.

    ⚠What it shows: Meta-analysis of 23 observational studies with substantial heterogeneity; prevalence data show association, not causation, and bipolar disorder numbers were far smaller than depression numbers.Review · J Clin Med

    Full breakdown →Mood Disorders and Obstructive Sleep Apnea: A Systematic Review and Meta-Analysis. J Clin Med 2026
18. Sleeppreliminary · human dataAdded 29 July 2026

    Sleep apnoea tied to lower fitness and higher mortality

    In 1001 middle-aged adults from a population-based cohort who underwent overnight polysomnography and cardiopulmonary exercise testing, a higher apnoea-hypopnoea index was associated with lower peak oxygen uptake and with all-cause mortality over a median 10.3 years (hazard ratios 1.31-1.72). Lower fitness did not statistically explain the mortality link.

    ⚠What it shows: Observational population cohort of 1001 adults, mean age 54, with only 73 deaths over follow-up and a single night of sleep testing: associations cannot establish cause, and the mediation analysis was underpowered.Study · ERJ Open Res

    Full breakdown →VO₂max explained →VO2max Calculator →Association of obstructive sleep apnoea with exercise capacity and mortality in a population-based study: results of SHIP-TREND. ERJ Open Res 2026
19. Sleeppreliminary · human dataAdded 29 July 2026

    Swimmers slept more with 09:00 starts but swam no faster

    Delaying morning training from 07:00 to 09:00 gave national-level swimmers 1.0 h more sleep per night on average, but recovery and 100 m and 800 m time-trial performance did not measurably improve over the 8-day camps.

    ⚠What it shows: One cross-over RCT in 27 adolescent national-level swimmers across two 8-day training camps; the extra sleep produced no significant recovery or performance change in that short window, and results may not generalise to older or recreational athletes.Study · Sports Med Open

    Full breakdown →Sleep Calculator →Delaying Early Morning Training Time in Swimmers: Effects on Sleep, Recovery and Performance-A Randomized Controlled Trial. Sports Med Open 2026

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