The Sleep Evidence: Five Sleep Problems and What Each Means for Dementia.
Five sleep problems, what each one is linked to, and which ones are worth acting on. This is the summary post for the series, written to stand on its own.
The Sleep Evidence, Part 4: Does Treating a Sleep Disorder Lower Dementia Risk?
Apnea and insomnia can be treated, so does treating them protect the brain? Nobody has run the trial that would answer it. What exists is observational data pointing toward benefit and a handful of randomized trials that get cited as proof it fails, when most were never built to detect success.
The Sleep Evidence, Part 3: Sleep Apnea, Insomnia, and REM Sleep Behavior Disorder
Three sleep disorders, three different relationships to dementia. Apnea and insomnia are treatable conditions that wire into the brain's overnight clearance. REM sleep behavior disorder is not a habit or a risk factor at all, but an early sign of a disease already underway.
The Sleep Evidence, Part 2: Does Sleep Clear the Brain of Alzheimer's Proteins?
During deep sleep, the brain clears out metabolic waste, including the amyloid protein tied to Alzheimer's. It is one of the most compelling mechanisms in brain health, and one of the most overstated. Here is what the glymphatic system actually does, and what it cannot yet prove in people.
The Sleep Evidence, Part 1: How Much Sleep, and How Well?
Sleep is the second pillar, and one of the most confusing. Both too little and too much sleep track with higher dementia risk, and cause runs in both directions. This series works through what the evidence on duration, quality, and timing actually supports, starting with why more is not safer.
Exercise and the APOE4 Brain: Does It Protect Carriers Differently?
If you carry APOE4, the strongest genetic risk factor for Alzheimer's, does exercise protect your brain the same way, more, or less? The evidence suggests the relationship may differ for carriers, but the signal is thinner than the confident headlines imply. Here is what actually holds up.
The Exercise Evidence: What Should You Actually Do for Your Brain?
After nine posts taking the evidence apart, here is what survives, and what it means for how you live. Not the headline promise that exercise prevents dementia, but a smaller, sturdier conclusion about what movement can and cannot do for the aging brain, and how to act on it honestly.
The Exercise Evidence, Part 9: How Much Exercise, and How Hard?
After all the trials, the most practical question is the hardest to answer cleanly: how much exercise, and how intense, actually matters for the brain? The dose evidence points to a moderate floor rather than a high ceiling, and to consistency over intensity, then it runs out faster than expected.
The Exercise Evidence, Part 8: Do Combined Lifestyle Changes Protect the Brain?
Exercise alone kept coming up short in the trials. So researchers stopped testing it in isolation and changed diet, activity, mental engagement, and blood pressure together. That is where the first genuinely positive prevention trials appeared, and where the picture finally starts to turn.
The Exercise Evidence, Part 7: Can Exercise Alone Protect the Brain?
The observational case was strong but confounded. So researchers ran the clean test: large randomized trials of exercise by itself, measured against real cognitive decline, before anyone added diet or mental training. The bigger and stricter the trial, the smaller the effect got.
The Exercise Evidence, Part 6: Does Exercise Protect the Brain, or Predict It?
Every study so far shared one weakness: people chose whether to exercise. So does activity protect the brain, or do the people destined to stay sharp simply stay active longer? Two studies were built to tell the difference, and their answer is sobering.
The Exercise Evidence, Part 5: Is Resistance Training Better for the Brain Than Aerobic?
The famous walking studies never replicated, but one form of exercise did move both cognition and brain structure together: lifting weights, in people already showing mild cognitive impairment. Here is the strongest single signal in the whole pillar, described precisely, and where it stops.