Evidence reviews on aging, lifespan, and healthspan.
26 claims reviewed
Weak evidence in humans: Caloric restriction dramatically extends lifespan in animals (worms, flies, mice), but human evidence is limited to biomarker improvements. No human study has proven lifespan extension.
Very weak evidence exists for health benefits of dry fasting beyond water fasting. Claims of enhanced autophagy and fat burning are largely theoretical. The few studies come from Ramadan observational data, which confounds dry fasting with caloric restriction and circadian changes.
Moderate evidence that fasting upregulates autophagy at a cellular level. Animal studies are unambiguous — fasting dramatically increases autophagy. In humans, recent trials measuring LC3 markers in blood cells show fasting does increase autophagic flux, but the health implications and optimal protocols remain unclear.
Weak evidence suggests prolonged fasting (48-72+ hours) may trigger hematopoietic stem cell regeneration and white blood cell renewal. Animal data is compelling, but human clinical evidence is very limited and confined to chemotherapy patients.
Growing evidence from systematic reviews links residential green space exposure to reduced all-cause mortality, with proposed mechanisms including increased physical activity, reduced air pollution, stress reduction, and improved social cohesion. However, confounding by socioeconomic factors remains a significant limitation.
Strong evidence supports grip strength as a robust predictor of all-cause mortality and longevity. Large prospective cohorts consistently show that lower grip strength independently predicts higher mortality risk, with hazard ratios of 1.3-1.7 per standard deviation decrease, even after adjusting for age, sex, and comorbidities.
Weak evidence connects heat shock protein (HSP) activation to slowed aging in humans. While HSPs demonstrably extend lifespan in model organisms and maintain proteostasis, translating these findings to human longevity interventions remains speculative with no clinical trials demonstrating anti-aging outcomes.
Weak evidence from ecological and cohort studies suggests altitude residence is associated with lower cardiovascular mortality, but confounding by lifestyle, genetics, and selective migration makes causal interpretation unreliable.
Moderate evidence suggests intermittent fasting improves some biomarkers associated with longevity (insulin sensitivity, inflammation, autophagy), primarily from animal studies and short-term human trials. However, direct evidence for lifespan extension in humans is lacking, and benefits may not exceed those of standard caloric restriction.
Strong evidence demonstrates that chronic loneliness and social isolation significantly increase all-cause mortality risk. Meta-analyses show a 26-29% increased risk of premature death for lonely individuals, comparable in magnitude to established risk factors like obesity and physical inactivity.
Weak evidence supports metformin slowing aging in non-diabetics. Observational studies in diabetic populations show reduced all-cause mortality compared to non-diabetics, and animal data is supportive. However, no completed RCTs in healthy humans demonstrate anti-aging effects, and emerging evidence suggests it may blunt exercise adaptations.
Multiple observational studies and meta-analyses suggest metformin use is associated with reduced cancer incidence in diabetic populations. However, time-related biases in study designs may significantly inflate these estimates, and large RCTs are ongoing to establish causality.
Weak evidence for anti-aging effects in humans. NAD+ precursors (NMN, NR) reliably increase blood NAD+ levels, but no human trials have demonstrated reversal of aging biomarkers, functional improvements, or lifespan extension. Animal data is promising but translation remains unproven.
Weak evidence supports nicotinamide riboside (NR) for anti-aging in humans. While NR reliably boosts NAD+ levels in blood, human trials have not demonstrated meaningful improvements in aging biomarkers, physical function, or healthspan outcomes despite strong preclinical data.
Moderate evidence from large prospective cohort studies consistently associates dispositional optimism with 10-15% reduced all-cause mortality and increased likelihood of exceptional longevity (85+ years). Mechanisms likely involve healthier behaviors, better stress physiology, and stronger social connections.
Moderate evidence from large cohort studies suggests dog ownership is associated with reduced all-cause mortality (approximately 24% reduction), likely mediated through increased physical activity and social connection. Evidence for other pets is weaker and inconsistent.
Large observational studies associate dog ownership with reduced cardiovascular mortality, and the American Heart Association acknowledges possible benefits. However, no causal evidence exists, and the association likely reflects confounding by physical activity and lifestyle factors.
Moderate evidence from large prospective cohort studies shows that individuals with a strong sense of purpose have 15-30% lower risk of developing Alzheimer's disease and related dementias. The mechanism likely involves cognitive reserve, healthier behaviors, and reduced chronic stress rather than a direct neuroprotective effect.
Weak evidence exists for rapamycin extending human lifespan. While rapamycin consistently extends lifespan in animal models (mice, yeast, worms, flies) by inhibiting mTOR, human longevity data is nonexistent. Off-label use is growing but lacks clinical trial support for healthy aging.
Moderate evidence from prospective cohort studies suggests frequent sauna use is associated with reduced dementia and Alzheimer's disease risk. However, the evidence is primarily observational from Finnish populations, and acute physiological effects do not confirm long-term neuroprotection.
Resveratrol dramatically extended lifespan in yeast, worms, and mice on high-fat diets. Human trials have shown minimal effects on aging biomarkers at doses achievable through supplements or diet.
Moderate evidence from large cohort studies associates frequent sauna use with reduced cardiovascular mortality and all-cause mortality, but causal proof from RCTs is lacking.
Strong evidence from multiple large meta-analyses demonstrates that robust social connections reduce all-cause mortality by 45-50%, with effect sizes comparable to smoking cessation and exceeding those of exercise or obesity interventions. Social isolation is now recognized as a major independent risk factor for premature death.
Weak evidence from animal studies and epidemiological data suggests spermidine may promote cellular health through autophagy induction. Human interventional evidence is limited to small, short-term trials showing modest cognitive and cardiovascular biomarker improvements.
Weak evidence from animal studies suggests taurine supplementation may extend lifespan and healthspan in mice and worms. A landmark 2023 Science paper sparked interest, but no human longevity trials exist and causal mechanisms remain speculative.
Strong evidence supports VO2max as one of the most powerful predictors of lifespan. Large cohort studies demonstrate a dose-response relationship between cardiorespiratory fitness and all-cause mortality, with the lowest-fit quartile having 3-5x higher mortality risk than the highest-fit quartile, rivaling the predictive power of smoking status.