Field
Body
Muscle, bone, heart and the tissues that set the pace of decline.
- Afternoon naps and sleep debt: what the experiments timedgoodTen minutes of sleep in the nap, thirty minutes of sleep in the nap. The difference is a measured period of worse performance, and self-ratings do not notice it.
- Alcohol and longevity: what the cohorts say and what the genetics saymixedTwo literatures, two shapes. The one that measures what people say they drink is J-shaped. The one that measures what their genes predispose them to is a straight line upwards. The gap between them is not a rounding error, it is the whole argument.
- Blood pressuresettledThe most consequential modifiable number in ageing. Usually silent until it isn't.
- Calorie restriction and ageing: what the human trials measured, and what they were built to avoidgoodThe best human trial of calorie restriction exists, ran for two years, and did not measure lifespan. It measured the predictors — and the costs are in the same table.
- Falls and bone densitysettledFracture risk is bone strength times falling. Most attention goes to the first half.
- Growth hormone after fifty: what two randomised trials actually measuredmixedTwo six-month trials, eighty men and twenty-one men, and a result that splits cleanly along the lines of what was combined with what.
- InflammagingthinChronic low-grade inflammation with age. Well observed; poorly actionable so far.
- Menopause and longevity: what the cohorts actually showmixedEarly menopause tracks with cardiovascular events. Whether it tracks with dying earlier is the part the cohorts disagree on.
- Omega-3 and ageing: what the trials measured when they measured telomeresmixedCardiovascular outcomes move a little. Telomere outcomes do not move in the biggest trial, and the field's supporting meta-analyses cover 337 people.
- Oral health and longevity: what four million people in a meta-analysis do and do not showmixedThe association is the largest pooled one in preventive medicine. The causal claim, tested with instruments that do not lie about confounding, is the weaker half.
- Resistance training and muscle aging: what the trials showgoodStrength responds at any age. Mass and daily function respond less, and the safety reporting is thin.
- Sarcopenia (muscle loss with age)settledThe default loss of muscle and strength with age. The most reversible thing on this list.
- Sauna bathing and the Finnish cohorts: what two decades of follow-up showmixedFrequent sauna use tracks with lower mortality in Finnish cohorts. Observational only; no trial has tested prescribing it.
- Short sleep and mortality: what the cohorts actually associategoodBelow seven hours, 1.14. Above nine hours, 1.34. The per-hour figure is 1.06. None of it is a randomised trial, and the authors of both analyses say so.
- Sleep and glucose metabolism: what the trials actually measuredgoodInsulin sensitivity falls when sleep is cut in controlled trials. The number is 11 to 20 percent over a week, or an HOMA-IR rise of 0.30 over six weeks.
- Sleep and immunity: what the inoculation experiments measuredgoodThe cold studies are experiments with an infection delivered on purpose. The inflammatory studies are experiments with sleep cut on purpose. Both point the same way and neither measures disease.
- Telomeres and longevity: the numbers from 121,749 people, and what they do not measuregoodA 2018 meta-analysis of 25 studies, 121,749 individuals and 21,763 deaths: one standard-deviation shorter leukocyte telomere length carried a hazard ratio of 1.09 for all-cause mortality, and the shortest quarter 26 per cent higher than the longest. A 2017 individual-participant analysis of 12,199 adults found 1.23 for the shortest quintile. The association weakens above 80 years.
- Ultra-processed food and mortality: what the pooled evidence actually gradesmixedThe largest pooled look at industrialised food and death, printed with its own certainty ratings.
- Vitamin D in older adultsgood15 µg a day; the case is bone and deficiency correction, not the longer list.