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1. 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
2. Physiologypreliminary · human dataAdded 6 August 2026

   Lifting raises IGF-1 after 60, lowers it before

   Pooling 22 studies with 680 participants, resistance training was associated with higher serum insulin-like growth factor 1 in people older than 60, in both men and women, while participants younger than 60 showed lower IGF-1. The effect appeared at training durations both under and over 16 weeks.

   ⚠What it shows: Meta-analysis of 22 mostly small studies totalling 680 participants, searched to May 2020. It pooled a continuous blood marker using odds ratios, an unusual approach, and IGF-1 is a circulating marker rather than a measure of strength, muscle mass or health outcomes. The reversal in under-60s was unexpected and is not explained.Meta-analysis · Aging Male

   Full breakdown →Resistance training effect on serum insulin-like growth factor 1 in the serum: a meta-analysis. Aging Male 2020
3. Cardiowell supported · human dataAdded 6 August 2026

   Fitness may shield workers from a hard job's toll

   Pooling five European cohorts of 9922 men followed for an average of 25.6 years, men with low cardiorespiratory fitness who reported high occupational physical activity had higher cardiovascular (HR 1.27) and all-cause mortality (HR 1.22) than low-fitness men with low occupational activity. Among high-fitness men the cardiovascular association was no longer clear, though the all-cause association persisted.

   ⚠What it shows: Individual participant data meta-analysis of five observational European cohorts, male workers only (mean age 46.8), with occupational activity self-reported. Observational design means association, not proof of cause, and the results may not transfer to women or to other kinds of work.Meta-analysis · Scand J Work Environ Health

   Full breakdown →VO₂max explained →VO2max Calculator →Exploring the 'fit for work' principle: The association between occupational physical activity, cardio-respiratory fitness, and mortality - a meta-analysis of male worker data. Scand J Work Environ Health 2025
4. Longevitywell supported · human dataAdded 6 August 2026

   Active later life tracks with longer, sharper years

   A coordinated analysis of 14 longitudinal studies covering 52,039 older adults found that more physical activity was associated with a lower risk of moving from unimpaired to mildly impaired cognition, a lower risk of death, and substantially longer estimated life expectancy. Evidence of benefit after impairment had already begun was present but less consistent between studies.

   ⚠What it shows: Pooled analysis of 14 observational cohorts (52,039 adults, mean baseline ages 69.9-81.73) from North America and Europe; physical activity was self-reported and not randomised, so this shows association, not proof that activity causes the slower decline. Findings after impairment onset varied substantially between studies.Meta-analysis · J Gerontol A Biol Sci Med Sci

   Full breakdown →Healthspan explained →Healthy Lifestyle & Life Expectancy →The Importance of Engaging in Physical Activity in Older Adulthood for Transitions Between Cognitive Status Categories and Death: A Coordinated Analysis of 14 Longitudinal Studies. J Gerontol A Biol Sci Med Sci 2021
5. Nutritionwell supported · human dataAdded 6 August 2026

   Low-carb traded lower triglycerides for higher LDL

   In a meta-analysis of randomised trials in people with overweight or obesity, hypocaloric low-carbohydrate diets were no better than low-fat diets for blood pressure, CRP, HDL, total cholesterol or body composition; they lowered triglycerides by 19.94 mg/dL but raised LDL by 20.00 mg/dL. Only very-low-carbohydrate versions significantly reduced flow-mediated dilation, a measure of blood-vessel function, by 2.12%.

   ⚠What it shows: Systematic review and meta-analysis of randomised trials in adults with overweight or obesity, with only 10 studies (n = 475) reporting the vascular outcome; diets were calorie-restricted, trial lengths and carbohydrate definitions varied, and the overall low-carb effect on vessel function was not statistically significant.Meta-analysis · Eur J Clin Nutr

   Full breakdown →ApoB explained →Macro Calculator →Hypocaloric low-carbohydrate versus low-fat diets on flow-mediated dilation, blood pressure, cardiovascular biomarkers, and body composition in individuals with overweight or obesity: a systematic review and meta-analysis of randomized clinical trials. Eur J Clin Nutr 2025
6. Trainingwell supported · human dataAdded 6 August 2026

   Weights cut HbA1c and blood pressure in type 2 diabetes

   A meta-analysis of 33 randomised trials in 1,396 middle-aged and older adults with type 2 diabetes found resistance training reduced the atherogenic index of plasma (effect size -0.56) and improved glycaemic control, lowering HbA1c by 0.62% and HOMA-IR by 0.90. Systolic blood pressure fell by 3.91 mmHg and body fat by 0.54%, while VO2max rose, with stronger effects in overweight or obese participants.

   ⚠What it shows: Meta-analysis of 33 randomised trials with a modest combined sample (n = 1,396) of middle-aged and older adults with type 2 diabetes; heterogeneity was substantial across several outcomes, methodological quality varied, and the included studies were geographically concentrated, so pooled effect sizes are indicative rather than precise.Meta-analysis · Maturitas

   Full breakdown →Insulin sensitivity explained →Metabolic Fitness Index →The impact of resistance training on the Atherogenic index of plasma and cardiometabolic health-related indicators in middle-aged and older adults with type 2 diabetes: A systematic review and Meta-analysis. Maturitas 2026
7. Women's Healthwell supported · human dataAdded 6 August 2026

   Exercise lowered inflammation, but volume wasn't the lever

   A meta-analysis of 30 randomised trials in 2,124 overweight or obese postmenopausal women found exercise training reduced TNF-alpha (SMD -0.47) and CRP (SMD -0.36), while IL-6 and adiponectin did not change significantly. Neither total weekly exercise volume nor programme duration showed a clear dose-response, and higher intensity was only borderline associated with larger TNF-alpha reductions (p = 0.063).

   ⚠What it shows: Meta-analysis of 30 randomised trials (N = 2,124) restricted to overweight and obese postmenopausal women, so it does not generalise to other groups. The intensity signal is a borderline meta-regression trend (p = 0.063), not a demonstrated threshold, and the authors' 'intensity threshold' framing goes beyond what that statistic establishes.Meta-analysis · Front Immunol

   Full breakdown →HIIT explained →Heart Rate Zone Calculator →Effects of exercise intensity and volume on systemic inflammation in overweight and obese postmenopausal women: a dose-response meta-analysis. Front Immunol 2026
8. Metabolic & GLP-1well supported · human dataAdded 6 August 2026

   GLP-1 drugs linked to lower fracture risk

   Pooling 54 randomised trials in 49,602 people with type 2 diabetes, GLP-1 receptor agonists were associated with a lower risk of bone fracture than placebo or other glucose-lowering drugs, and exenatide ranked as the most favourable agent (RR 0.17, 95% CI 0.03-0.67). A statistically significant inconsistency appeared in some of the indirect comparisons.

   ⚠What it shows: Bayesian network meta-analysis of 54 RCTs (49,602 participants, 28,353 on GLP-1 RAs) in people with type 2 diabetes, not healthy adults. Fractures were rarely the trials' main outcome, the exenatide estimate rests on very few events with a wide confidence interval, and the network showed significant inconsistency in some comparisons, so drug rankings are fragile.Meta-analysis · Osteoporos Int

   Full breakdown →Glucagon-like peptide-1 receptor agonists and fracture risk: a network meta-analysis of randomized clinical trials. Osteoporos Int 2018
9. Metabolic & GLP-1preliminary · human dataAdded 6 August 2026

   Bigger weight loss, bigger heart benefit on GLP-1s

   Pooling 8 cardiovascular outcome trials of GLP-1 receptor agonists in type 2 diabetes (60079 patients), the trials that lowered HbA1c and body weight most also showed the largest reductions in major cardiovascular events, at an estimated 25% lower relative risk per 1% absolute HbA1c reduction and 7% per 1 kg of weight lost. Reductions in systolic blood pressure and LDL cholesterol were not associated with event reduction.

   ⚠What it shows: Trial-level meta-regression across 8 cardiovascular outcome trials (60079 patients, 30693 on GLP-1 RAs) in type 2 diabetes. Because it correlates average results between trials rather than tracking individuals, it cannot show that losing weight caused the event reduction, and the weight-loss association was only just statistically significant (p = 0.047).Meta-analysis · Cardiovasc Drugs Ther

   Full breakdown →Heart Age Calculator →Association Between the Magnitude of Glycemic Control and Body Weight Loss With GLP-1 Receptor Agonists and Risk of Atherosclerotic Cardiovascular Disease: A Systematic Review and Meta-analyses of Randomized Diabetes Cardiovascular Outcomes Trials. Cardiovasc Drugs Ther 2025
10. Gut & Microbiomewell supported · human dataAdded 6 August 2026

    Probiotics shifted PCOS blood sugar, not the scales

    Pooling 8 randomised trials in women with polycystic ovary syndrome, probiotic or synbiotic supplements produced small reductions in fasting blood sugar (-2.52 mg/dl), insulin (-2.27 uIU/mL), HOMA-IR (-0.69), C-reactive protein and total testosterone (-0.12 ng/mL). Weight and body mass index did not change significantly.

    ⚠What it shows: Meta-analysis of only 8 RCTs (nine treatment arms) in women with polycystic ovary syndrome, searched to September 2018. The individual trials were small and short, effect sizes are modest, strains and doses varied between studies, and the findings do not transfer to women without PCOS.Meta-analysis · Eur J Clin Nutr

    Full breakdown →Insulin sensitivity explained →Metabolic Fitness Index →Effect of probiotics and synbiotics on selected anthropometric and biochemical measures in women with polycystic ovary syndrome: a systematic review and meta-analysis. Eur J Clin Nutr 2020
11. Supplementswell supported · human dataAdded 6 August 2026

    Probiotics nudged spine bone density, not bone markers

    Pooling randomised trials, probiotic supplementation produced small increases in lumbar spine areal bone mineral density (+0.010) and hip aBMD (+0.022 g/cm2), with no significant effect on femoral neck density or on the bone turnover markers P1NP and CTX. Most included trials were in postmenopausal women.

    ⚠What it shows: Systematic review and meta-analysis of randomised trials (16 comparisons for lumbar spine, 9 for hip, 7 for femoral neck), mostly in postmenopausal women, with moderate-to-high heterogeneity throughout; the hip effect became non-significant when key trials were removed, and no fracture outcomes were pooled.Meta-analysis · Osteoporos Int

    Full breakdown →Probiotic Supplementation and Bone Health Parameters in Adults: A Systematic Review and Meta-Analysis. Osteoporos Int 2026
12. Metabolic & GLP-1preliminary · human dataAdded 6 August 2026

    Prebiotics left blood sugar untouched in prediabetes

    Across 11 randomised trials in 546 adults with prediabetes, prebiotic supplementation did not significantly change fasting glucose, insulin, HbA1c, HOMA-IR or blood lipids, and did not shift BMI or waist circumference. The single significant result was a reduction in body fat percentage, rated very low certainty.

    ⚠What it shows: Systematic review and meta-analysis of 11 randomised trials totalling 546 adults with prediabetes; the authors themselves rate certainty in the pooled estimates as very low for most outcomes, and the one positive finding sits on a wide confidence interval.Meta-analysis · J Nutr

    Full breakdown →Insulin sensitivity explained →Metabolic Fitness Index →Effect of Prebiotic Supplementation on Health Status in Adults with Prediabetes: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. J Nutr 2025
13. Nutritionwell supported · human dataAdded 6 August 2026

    Higher fibre intake tracks with 22% lower cancer risk

    An umbrella review pooling meta-analyses of observational studies linked higher dietary fibre intake to a 22% lower cancer risk and 17% lower cancer mortality, with the strongest inverse association for digestive tract cancers and a smaller one for breast cancer. Observational data cannot establish cause.

    ⚠What it shows: Umbrella review and meta-meta-analysis of 25 papers and 28 reports, all built on observational epidemiology: people who eat more fibre differ in many other ways, and no randomised trial evidence is included, so causation is not established.Meta-analysis · Crit Rev Food Sci Nutr

    Full breakdown →High and low dietary fiber consumption and cancer risk: a comprehensive umbrella review with meta-meta-analysis involving meta-analyses of observational epidemiological studies. Crit Rev Food Sci Nutr 2025
14. Mindpreliminary · human dataAdded 6 August 2026

    Probiotics fell short on older adults' cognition

    Across 20 randomised trials in older adults, probiotic supplementation showed a small positive trend on cognitive test scores and a reduction in inflammatory markers, but neither reached statistical significance. Heterogeneity between trials was high enough that no true overall effect size could be determined.

    ⚠What it shows: Meta-analysis of 20 randomised controlled trials in older adults; both pooled effects had confidence intervals crossing zero, and the authors state that high heterogeneity prevents determining a true overall effect size.Meta-analysis · Benef Microbes

    Full breakdown →Executive function explained →The role of probiotics in the improvement of cognitive performance of older adults: a meta-analysis. Benef Microbes 2025
15. Cardiowell supported · human dataAdded 6 August 2026

    HIIT ranked top for VO2max, resistance training last

    A Bayesian network meta-analysis of 93 randomised trials in 4,446 adults with overweight or obesity found that all six exercise types tested improved VO2max, with high-intensity interval training ranked highest and resistance training alone ranked least effective.

    ⚠What it shows: Network meta-analysis of 93 randomised trials with 4,446 adults living with overweight or obesity; rankings come from indirect statistical comparison rather than head-to-head trials, and the pooled effect sizes are unusually large, which suggests variation in how VO2max was measured across studies.Meta-analysis · J Sports Sci

    Full breakdown →VO₂max explained →VO2max Calculator →Comparative effectiveness of various exercise interventions on cardiorespiratory fitness in adults living with overweight or obesity: A systematic review and Bayesian network meta-analysis. J Sports Sci 2025
16. Mindwell supported · human dataAdded 6 August 2026

    Any exercise, not the combo, may boost older brains

    Combined aerobic and resistance training improved global cognition in healthy adults aged 65 and over compared with doing nothing, but a meta-analysis of 12 randomised trials found it was no better than active comparison conditions.

    ⚠What it shows: Meta-analysis of 12 RCTs (2557 healthy adults aged 65+); the overall pooled effect was non-significant, benefit appeared only against passive controls, and heterogeneity was moderate.Meta-analysis · Exp Gerontol

    Full breakdown →The regular effects of concurrent aerobic and resistance exercise on global cognition in healthy elderly populations: A systematic review with meta-analysis of randomized trials. Exp Gerontol 2025
17. 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 →Efficacy of therapies based on muscle strength training among individual with obstructive sleep apnea - a systematic review and meta-analysis. Respir Med 2026
18. Mindpreliminary · human dataAdded 6 August 2026

    Exercise may quiet rumination in depression

    In adults with depression, regular exercise reduced rumination and improved cognitive shifting in a meta-analysis of randomised trials, with benefits tied to specific doses: moderate-intensity aerobic sessions for rumination and high-intensity aerobic training for shifting. Inhibition and updating did not improve significantly.

    ⚠What it shows: Meta-analysis pooling few RCTs per outcome (5-9 studies, 260-832 participants); dose effects come from subgroup analyses, and the authors themselves call the findings preliminary and tentative.Meta-analysis · Psychol Sport Exerc

    Full breakdown →Executive function explained →Heart Rate Zone Calculator →Effects of chronic exercise on different central features of depression in adults with depression: A systematic review and meta-analysis of random controlled trials. Psychol Sport Exerc 2025
19. Environmentwell supported · human dataAdded 6 August 2026

    Particle pollution and death: likely cause, not chance

    A critical appraisal of 15 published reviews concluded that the short-term association between airborne particles and cardiopulmonary mortality is valid and satisfies most standard criteria for causality, with effects observed even where air quality standards were respected.

    ⚠What it shows: A 2001 critical assessment of the arguments in 15 existing reviews of ecological time-series studies, not a pooled analysis of individual data; time-series designs compare days rather than people, and the exposure landscape has changed since publication.Meta-analysis · J Air Waste Manag Assoc

    Full breakdown →All-cause mortality explained →Healthy Lifestyle & Life Expectancy →Air pollution and health: correlation or causality? The case of the relationship between exposure to particles and cardiopulmonary mortality. J Air Waste Manag Assoc 2001
20. Environmentpreliminary · human dataAdded 6 August 2026

    Beijing's cleaner air came with a smaller daily death toll

    Across five periods in Beijing between 1990 and 2017, concentrations of SO2, NO2, PM10 and PM2.5 fell by up to 42%, 10%, 33% and 15%, and the estimated short-term mortality effect of each pollutant shrank alongside them: PM2.5's effect on cardiovascular and respiratory deaths falling by up to 0.33% and 0.13%.

    ⚠What it shows: Longitudinal comparative study in one city: published effect estimates for 1990-2013 pooled by random-effects meta-analysis and combined with newly analysed 2015-2017 daily data. The design is ecological, so parallel changes in healthcare, smoking or population structure cannot be excluded.Meta-analysis · Chemosphere

    Full breakdown →All-cause mortality explained →Healthy Lifestyle & Life Expectancy →The impacts of continuous improvements in air quality on mortality in Beijing: A longitudinal comparative study. Chemosphere 2022
21. Environmentwell supported · human dataAdded 6 August 2026

    Long-term PM2.5 linked to worse Covid outcomes

    In a meta-analysis of cohort studies with individual-level data, each 1 µg/m3 increase in long-term PM2.5 exposure was associated with a 4% higher risk of SARS-CoV-2 infection, an 11% higher risk of COVID-19 hospitalisation and a 9% higher risk of COVID-19 death; NO2 was associated with hospitalisation and death, while ozone showed no association with any outcome.

    ⚠What it shows: Systematic review and random-effects meta-analysis restricted to cohort studies with individual-level data, pooled only where more than three studies existed per exposure-outcome pair. Observational throughout, so residual confounding remains possible, and country of study explained much of the heterogeneity between results.Meta-analysis · Environ Pollut

    Full breakdown →Investigating links between long-term air pollution exposure and the risk of SARS-CoV-2 infection, COVID-19 hospitalisation and mortality: a systematic review and meta-analysis of cohort studies. Environ Pollut 2025
22. Environmentpreliminary · human dataAdded 6 August 2026

    Cold snaps raise stroke deaths days after they hit

    Across 12 counties in Hubei, China, covering 42 739 stroke deaths between 2009 and 2012, cold spells were associated with a pooled stroke mortality risk of 1.180 at lags of 3-14 days, with the effect appearing after a delay of 2-3 days and lasting about 10 days, while heatwaves carried a pooled risk of 1.114 concentrated in the first 0-2 days.

    ⚠What it shows: Observational multivariate meta-analysis pooling daily mortality and weather records from 12 counties in one Chinese province over four years; ecological time-series design with no individual data, and county-level estimates varied widely, from 0.968 to 1.523 for cold spells.Meta-analysis · Zhonghua Liu Xing Bing Xue Za Zhi

    Full breakdown →All-cause mortality explained →[Impact of daily mean temperature, cold spells, and heat waves on stroke mortality a multivariable Meta-analysis from 12 counties of Hubei province, China]. Zhonghua Liu Xing Bing Xue Za Zhi 2017
23. Environmentwell supported · human dataAdded 6 August 2026

    Extreme cold outranks heat as the deadlier extreme

    Pooling 58 observational studies, extreme cold carried the highest all-cause mortality risk at a relative risk of 1.478, above heatwaves at 1.280 and extreme heat at 1.145; heatwaves were also associated with more hospitalisations (1.060) and emergency department visits (1.047).

    ⚠What it shows: Systematic review and meta-analysis of 58 observational studies published between 2000 and 2024, so all estimates are associations from population records rather than controlled comparisons; definitions of extreme cold, extreme heat and heatwave vary between studies, and few studies covered length of stay or costs.Meta-analysis · Int J Hyg Environ Health

    Full breakdown →A systematic review and meta-analysis comparing the health burden of extreme heat and cold on mortality and urgent care utilization. Int J Hyg Environ Health 2026
24. Environmentwell supported · human dataAdded 6 August 2026

    Heat plus high ozone: mortality risks stack up

    In a meta-analysis of 28 studies, days combining heat with high ozone were associated with a 17% higher overall mortality risk than days without co-exposure, with elevated cardiovascular and respiratory mortality and increased risks across age and gender groups and in urban areas.

    ⚠What it shows: Systematic review of 78 studies with 28 pooled by random-effects meta-analysis; all observational, with the authors flagging risk of bias from inadequate confounder adjustment and unclear handling of missing data, plus inconsistent definitions of what counts as a compound heat-ozone event.Meta-analysis · Environ Pollut

    Full breakdown →All-cause mortality explained →Effect of compound heat and ozone events on health outcomes: a systematic review and meta-analysis of epidemiological evidence. Environ Pollut 2026

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