Study archive

Pooled results from randomised trials found Tai chi improved sleep quality in people with insomnia, lowering Pittsburgh Sleep Quality Index scores by 1.75 points, and also reduced depression and anxiety scores.

⚠What it shows: Promising but imperfect: results pooled from several randomised trials of people with insomnia all pointed the same way. Participants inevitably knew they were practising Tai chi and many trials described their methods thinly, so expectation could explain part of the benefit.Meta-analysis · Int J Environ Res Public Health

Pooled across six randomised trials in 1,069 adults with moderate to severe obstructive sleep apnoea, GLP-1 based drugs (liraglutide or tirzepatide) cut apnoea events by about 10 per hour and body weight by 9.68 kg versus control, with small blood pressure reductions too. Oxygen measures during sleep did not significantly improve, and the reviewers stress the drugs are not a substitute for CPAP.

⚠What it shows: Solid enough to take seriously: results pooled from six trials where people were assigned at random, 1,069 adults in total, all testing liraglutide or tirzepatide. The trials disagreed with each other on how big the benefits were, so treat the exact figures loosely, and the oxygen dips that make apnoea harmful did not clearly improve.Meta-analysis · Sleep Breath

Warm foot baths before bed, typically with water above 40 degrees Celsius, were linked to better sleep quality in older adults in 9 of the 10 studies reviewed.

⚠What it shows: Encouraging but not yet rigorous: a sweep of 10 small studies in older adults, not all of them properly randomised. The results pointed the same way, but nobody has pooled the numbers to say how big the benefit actually is.Systematic review · BMC Geriatr

Across 18 randomised trials in people with sleep disorders, traditional Chinese mind-body exercise improved outcomes: tai chi combined with transcranial magnetic stimulation ranked best for sleep quality, while tai chi and Baduanjin both significantly improved quality of life.

⚠What it shows: Decent but messy evidence: pooled results from 18 trials where people were assigned at random, and the trials disagreed with each other on how big the benefits were. The standout sleep result also required transcranial magnetic stimulation alongside the exercise, which is clinic equipment rather than something you can do at home.Systematic review · Front Psychiatry

A systematic review of 20 studies found that women's physical activity across the menopausal transition is held back by barriers such as existing health complaints, and supported by enablers including awareness of the health benefits, social support, feeling safe, injury prevention and confidence in their own ability to exercise.

⚠What it shows: A solid map of the problem rather than a tested fix: it pools 20 studies on what helps and hinders women's activity through menopause. Few of those studies were built on behaviour theory, so some influences may have been missed entirely.Systematic review · Menopause

In pooled results from seven randomised trials in 3,184 perimenopausal and postmenopausal women with moderate to severe hot flushes, neurokinin receptor antagonists improved self-reported sleep disturbance versus placebo at 4, 12 and 24 weeks, with elinzanetant showing a larger effect than fezolinetant. The certainty of the evidence was rated low because the trials disagreed on the size of the benefit.

⚠What it shows: Promising but not settled: results pooled from seven placebo-controlled trials in 3,184 women consistently favoured the drugs, yet the studies disagreed so much on the size of the benefit that the reviewers rated the evidence low certainty. The gains were also measured in women with moderate to severe hot flushes, so this says nothing about menopausal sleep trouble without them.Study · Menopause

Pooled results from five randomised trials in 242 mothers with mild-to-moderate postpartum depression found walking programmes reduced depression scores by 4.01 points on the Edinburgh scale compared with controls, a drop the authors call clinically significant. Supervised, group-based plans including 90-120+ minutes of moderate walking per week looked most promising.

⚠What it shows: Encouraging but thin: just five trials with 242 women in total, all with mild-to-moderate symptoms, and the studies disagreed with each other a fair bit. Treat the size of the benefit as a rough estimate rather than a settled figure.Meta-analysis · J Womens Health (Larchmt)

Exercise reduced depressive symptoms around pregnancy in a pooled analysis of nine randomised trials, with a moderate overall effect; the benefit was clear during pregnancy but close to zero when exercise happened in the postpartum period.

⚠What it shows: Real but fragile: results pooled from just nine trials where women were assigned at random, and those trials disagreed with each other a lot. The benefit showed up when exercise happened during pregnancy; postnatal programmes barely moved symptoms.Meta-analysis · Int J Public Health

Pooled across 24 randomised trials, folic acid supplementation lowered fasting blood glucose by 2.17 mg/dL and fasting insulin by 1.63 pmol/L, with a small drop in insulin resistance scores, but HbA1c did not change. The authors call the reductions small enough to limit clinical application.

⚠What it shows: Real but tiny: pooled results from 24 trials in adults show drops in fasting glucose and insulin that are statistically clear yet too small to matter much to anyone managing their blood sugar. HbA1c, the marker that reflects blood sugar over months, did not move at all.Meta-analysis · Nutrients

Creatine supplementation did not improve recovery of muscle strength, soreness, range of motion or inflammation after muscle-damaging exercise across pooled trials; the only change was a lower blood marker of muscle damage at 48 hours.

⚠What it shows: A solid null: results pooled from 13 trials covering 278 people, mostly men aged 20 to 60. The trials disagreed with each other quite a bit, so the authors still want bigger, tighter studies before closing the book.Meta-analysis · Int J Sport Nutr Exerc Metab

Citrulline malate did not improve muscle strength in resistance-trained adults when four randomised trials were pooled, with 69 assessments on the supplement and 69 on placebo; upper and lower body results were equally flat.

⚠What it shows: A credible null: results pooled from four trials where trained lifters were assigned at random to citrulline malate or a placebo, 69 assessments in each group. Only four trials made the cut, so a small effect hiding below detection cannot be completely ruled out.Meta-analysis · J Diet Suppl

In adults with early-stage cardio-kidney-metabolic syndrome, those with the highest triglyceride-glucose index scores had up to 45% higher risk of developing cardiovascular disease than those with the lowest, in pooled data from nine studies that followed people over time.

⚠What it shows: A consistent link, not proof of cause: it pools nine studies that followed people rather than testing anything on them, and the studies disagreed with each other quite a bit. The populations studied were not very diverse, so the picture may differ elsewhere.Meta-analysis · BMC Cardiovasc Disord

Across five randomised trials in 4,227 people with high cholesterol, oral PCSK9 inhibitor pills lowered LDL cholesterol by as much as 61.8 percentage points more than placebo, with higher doses doing more and no short-term safety signal. Which pill or dose is best remains uncertain.

⚠What it shows: Big effects but early days: results pooled from five trials in 4,227 people show large LDL drops against placebo, yet nearly all pill-versus-pill comparisons were indirect and the authors rate the overall certainty as low. Safety was only tracked over the short term.Meta-analysis · Endocrine

In a network meta-analysis of 86 randomised trials covering 4358 adults with overweight or obesity, every exercise modality improved insulin-resistance markers versus usual care, with HIIT ranking highest and benefits peaking around 1000-1200 MET-minutes per week. Adding calorie restriction to exercise showed no significant extra benefit for these markers.

⚠What it shows: Strong on the big picture, softer on the rankings: results pooled from 86 trials in 4358 adults with overweight or obesity. The certainty was rated low to moderate, and HIIT's top spot relies partly on indirect comparisons that still need head-to-head trials.Study · Diabetes Obes Metab

Letting your arm hang by your side during a blood pressure check added 6.5 mm Hg to systolic readings compared with proper desk support in a randomised crossover trial of 133 adults, and resting the hand in the lap added 3.9 mm Hg. Either habit could make normal blood pressure look like hypertension.

⚠What it shows: Worth taking seriously: each of the 133 adults was measured in every arm position in random order, so everyone acted as their own control and the comparison is clean. It captured readings at a single visit, though, so it shows how the numbers get skewed rather than how often that leads to a wrong diagnosis.RCT · JAMA Intern Med

In a pooled analysis of 17 studies following 176,862 people with coronary heart disease, leisure-time activity equivalent to about 150 minutes a week of moderate exercise was associated with 38% lower all-cause mortality; at much higher activity levels the estimates became too uncertain to call.

⚠What it shows: Strong as associations go, but these 17 studies followed 176,862 people rather than testing exercise on them, so healthier patients may simply have moved more. Above moderate doses the data thinned out badly, and the shape of the curve up there changed depending on how activity was estimated.Study · Eur J Prev Cardiol

A pooled analysis of 115 studies covering 199,055 healthy people found that nutrient supplements had little to no effect on preventing viral respiratory tract infections. The only signals were narrow: zinc appeared protective for children in Asia, and vitamin D modestly reduced infections in adults, mainly in North America.

⚠What it shows: As strong as this kind of evidence gets: results pooled from 115 studies covering 199,055 people in 37 countries, though the vast majority were children. The two positive signals, zinc and vitamin D, were regional and the studies behind them disagreed with each other, so even those deserve caution.Meta-analysis · Allergy

Pooled results from 14 randomised trials suggest probiotic supplements did not cut the number or length of respiratory infections in elite athletes, but they did reduce total symptom severity and lowered the inflammatory markers interleukin 6 and tumour necrosis factor alpha.

⚠What it shows: Reasonably solid for what it claims: results pooled from 14 trials in elite athletes, so the benefit may not carry over to everyday exercisers. The right strain, dose and timing are still unknown.Meta-analysis · J Athl Train

A review of 48 studies covering more than 3 million people found that the grip strength tests used to predict mortality are wildly inconsistent: only half controlled body position, and recorded strength shifted depending on which details of the test were standardised.

⚠What it shows: A credibility check on the measurement, not a new health finding: a sweep of 48 studies that followed more than 3 million people showed grip testing methods vary hugely from study to study. It cannot say which protocol is correct, only that the inconsistency skews the numbers.Meta-analysis · Clin Nutr

Across 24 randomised trials in 1,809 older adults, probiotic and synbiotic supplements showed early positive signals for cognitive scores and handgrip strength, but the trials disagreed widely and the muscle effect vanished when a single influential study was removed.

⚠What it shows: Treat this as a hint, not a verdict: results pooled from 24 trials in 1,809 older adults, but the studies disagreed sharply with each other and the grip strength benefit disappeared once one trial was excluded. Follow-up was short, so nobody knows whether any effect lasts.Systematic review · Front Nutr

Across 31 trials in 9,437 middle-aged and older men, testosterone replacement therapy lowered total cholesterol, triglycerides and LDL cholesterol and improved measures of artery health, but arrhythmias were more common in men on treatment.

⚠What it shows: Solid on the risk markers, unresolved on heart rhythm: results pooled from 31 trials in 9,437 middle-aged and older men with low or low-normal testosterone, lasting from 40 days to 36 months. The extra arrhythmias showed up clearly in the data, but their real-world clinical importance remains uncertain.Meta-analysis · Endocrine

A meta-analysis of 14 randomised trials in 1,284 people with functional constipation found fibre supplements added 1.42 bowel movements a week and improved stool consistency, with soluble, fermentable fibres above 10 g a day for at least 4 weeks working best. Fibre also shifted gut-brain markers such as short-chain fatty acids and serotonin, though the clinical meaning of those changes is not yet established.

⚠What it shows: Solid for the symptom relief, speculative for the brain story: results pooled from 14 trials in 1,284 people, with moderate to high certainty for the bowel outcomes. The biomarker shifts only hint at a mechanism and do not prove fibre acts on the gut-brain axis.Study · Clin Transl Gastroenterol

Pooled results from four trials in adults with chronic low back pain found that exercise programmes lasting six weeks or more reduced pain, yet serum cortisol levels went up rather than down.

⚠What it shows: An early signal only: four trials with 169 people between them, and the studies disagreed with each other on how big both effects were. Whether the cortisol rise matters for recovery is simply not known yet.Meta-analysis · Pain Manag

A systematic review found little evidence that wearable devices such as Fitbit improve chronic disease outcomes. Across 6 trials, only one showed a significant weight loss benefit and one a significant drop in long-term blood sugar in older adults with type 2 diabetes, with no significant reduction in cholesterol or blood pressure.

⚠What it shows: Strong method, thin material: a sweep of all the studies on this up to 2018 turned up just 6 usable trials, so the fairest verdict is that health benefits are unproven rather than disproven. Only one trial even measured long-term blood sugar, so for most outcomes the evidence is a handful of small studies.Systematic review · Am J Med