Alzheimer's Disease & Other Dementias

References & Evidence Notes

Each numbered entry below is either a source you can follow or a note setting out what the evidence does and does not support. Both are numbered together so the markers in the text line up.

Last reviewed October 20, 2026. Supplement entries are cross-checked against the NIH National Center for Complementary and Integrative Health and the Linus Pauling Institute Micronutrient Information Center.³¹ Be careful in this area, because desperation and expensive protocols meet here. No intervention has been shown in a controlled trial to reverse established Alzheimer's disease. What the evidence does support is worth doing: managing cardiovascular risk, treating hearing loss, exercise, sleep, social and cognitive engagement, and not smoking are associated with lower dementia risk, and a multidomain program showed modest cognitive benefit in a large randomized trial. Be skeptical, in proportion to the price, of any protocol promising reversal, any supplement stack sold for memory and any clinic charging heavily for either. If cognitive change is new, get assessed: depression, thyroid disease, B12 deficiency, sleep apnea and medication effects all cause reversible cognitive impairment and are missed regularly.

1. On what Alzheimer's is: a progressive neurodegenerative disease with amyloid plaques and tau tangles, beginning 15 to 20 years before symptoms. It is the most common cause of dementia but not the only one; vascular, Lewy body and frontotemporal dementias differ in presentation and management, and mixed pathology is common. ↩
2. On supplements: no supplement has been shown to prevent or treat Alzheimer's disease. Ginkgo biloba failed in large prevention trials: in the GEM trial, 3,069 people aged 75 or older took 120 mg twice a day or placebo for a median of 6.1 years, and ginkgo did not reduce dementia or Alzheimer's disease, including in those who started with mild cognitive impairment, PubMed 19017911. Vitamin E has limited and inconsistent evidence in established disease and carries risk at high doses. B vitamins lower homocysteine with no reliable cognitive benefit except possibly where deficiency exists. Coconut oil, ketones and most memory formulations lack supporting trials. ↩
3. On the forms of dementia and planning ahead: the World Health Organization states that Alzheimer's disease is the most common form of dementia and contributes to 60 to 70% of cases, with vascular, Lewy body and frontotemporal dementia among the other forms and mixed forms common; that no treatment ends it, but that a lot can be done to support people and those who care for them; and it advises planning ahead while decisions are easier, WHO, dementia. ↩
4. On modifiable risk: the 2024 Lancet Commission lists 14 potentially modifiable risk factors for dementia (less education, hearing loss, high blood pressure, smoking, obesity, depression, physical inactivity, diabetes, drinking more than 12 US drinks a week, traumatic brain injury, air pollution, social isolation, untreated vision loss and high LDL cholesterol) and reports stronger evidence than before that tackling them reduces risk, PubMed 39096926. It estimates that about 45% of dementia cases worldwide are attributable to these factors, a population calculation that assumes the links are causal, PubMed 40823285. ↩
5. On mild cognitive impairment: a neurology practice guideline found that 14.9% of people over 65 with mild cognitive impairment developed dementia over 2 years, that no high-quality evidence supports medicines for it, and that exercise training is likely to improve cognitive measures, PubMed 29282327. ↩
6. On how long people live with the disease: MedlinePlus states that people with Alzheimer's disease usually survive 8 to 10 years after symptoms appear, but that the course of the disease can range from 1 to 25 years, MedlinePlus, Alzheimer disease. ↩
7. On how many people are affected and at what cost: the Alzheimer's Association estimates that 7.4 million Americans aged 65 and older are living with Alzheimer's in 2026, projected to reach nearly 13 million by 2050; that almost two-thirds of Americans with Alzheimer's are women; and that health and long-term care costs for people with Alzheimer's and other dementias are projected to reach $409 billion in 2026, not including the value of unpaid care, Alzheimer's Association, Facts and Figures. ↩
8. On reversible causes: looking for them is the first practical step. Depression, hypothyroidism, vitamin B12 deficiency, obstructive sleep apnea, alcohol, and anticholinergic and sedative medication all cause cognitive impairment that improves when addressed. A structured assessment looks for these, and finding one changes everything. ↩
9. On causes: the National Institute on Aging states that the causes are not yet fully understood and probably combine age-related brain changes with genetic, health and lifestyle factors; that age is the biggest known risk factor, with about 1 in 13 people aged 65 to 84 and 1 in 3 aged 85 and older living with Alzheimer's; that the APOE4 variant raises risk but some carriers never develop the disease; that high blood pressure, diabetes, obesity, hearing loss, depression and head injury are linked with risk; and that researchers cannot yet say for certain whether changing lifestyle factors prevents dementia, NIA, what causes Alzheimer's disease. ↩
10. On homocysteine: in a cohort of 1,092 older adults, a homocysteine level above 14 micromol per liter went with nearly double the risk of Alzheimer's disease, PubMed 11844848. In a 2-⁠year randomized trial in 168 people over 70 with mild cognitive impairment, folic acid 0.8 mg, vitamin B12 0.5 mg and vitamin B6 20 mg a day slowed brain shrinkage on MRI from 1.08% to 0.76% a year, and by 53% in those with homocysteine above 13; the trial measured scans, not whether dementia was delayed, PubMed 20838622. ↩
11. On vitamin D and dementia: in a cohort of 1,658 older adults, vitamin D deficiency went with a higher risk of dementia (about 1.5 times with levels of 25 to 50 nmol/L, about 2.2 times below 25), rising most clearly below 50 nmol/L (20 ng/mL), PubMed 25098535. In a randomized trial in over 4,000 adults aged 60 and older, vitamin D3 at 2,000 IU a day did not slow cognitive decline over 2 to 3 years, PubMed 34853363. ↩
12. On modifiable risk across the lifespan: the Lancet Commission's risk factors (listed in full in note 4) act at different stages of life, from less education in early life, through most of the factors in midlife, to social isolation, air pollution and untreated vision loss in later life, so lowering risk is worth starting in midlife or earlier. Hearing loss is among the largest and most treatable, and hearing aids are among the more concrete things available. ↩
13. On the MIND diet cohort: in a Chicago study of 923 older adults followed for about 4.5 years, the highest third of MIND diet scores had a 53% lower rate of Alzheimer's disease and the middle third a 35% lower rate than the lowest third; this is an observational association, PubMed 25681666. ↩
14. On diet: the MIND diet, combining Mediterranean and DASH elements, is associated with slower cognitive decline in observational cohorts. A randomized trial of the MIND diet published in N Engl J Med in 2023 found no significant difference in cognitive change compared with a mild calorie-restricted control, with both groups improving. The observational association is real; the trial did not confirm a specific effect. Eat this way for cardiovascular reasons, which are well supported, and treat cognitive benefit as unproven. ↩
15. On blood pressure targets in older people: the NICE hypertension guideline sets a clinic target below 140/90 for most adults under 80 and below 150/90 for adults aged 80 and over, advises clinical judgment for people with frailty or multimorbidity, and advises checking for a drop in blood pressure on standing in people aged 80 and over, treating to a standing target where the drop is significant, NICE NG136. ↩
16. On blood sugar targets: American College of Physicians guidance advises personal HbA1c goals for type 2 diabetes, an HbA1c between 7% and 8% for most people on treatment, easing treatment below 6.5%, and not targeting an HbA1c at all in people with dementia and a limited life expectancy, because the harms outweigh the benefits, PubMed 29507945. ↩
17. On multidomain intervention, and on commercial protocols. The FINGER trial randomized 1,260 at-risk older adults to diet, exercise, cognitive training and vascular risk management, and found a modest benefit on cognitive performance; it is the strongest evidence in this area and the basis for taking the lifestyle approach seriously. A commercial protocol sold for Alzheimer's disease is frequently cited alongside it but has been published as small uncontrolled case series without a control group, and its results cannot be interpreted the same way. Presenting the two as equivalent evidence is not defensible, particularly where the protocol carries substantial cost. ↩
18. On new drug treatments: anti-amyloid monoclonal antibodies slow decline modestly in early disease, with meaningful risks including brain swelling and microhemorrhage, substantial cost and demanding monitoring. Whether the benefit is clinically noticeable is genuinely debated. This belongs with a specialist rather than in a supplement discussion. ↩
19. On the size of the anti-amyloid effect: in the main 18-⁠month trial of one anti-amyloid antibody in 1,795 people with early Alzheimer's disease, decline on a dementia rating scale was 0.45 points smaller than on placebo on an 18-⁠point scale, which the investigators described as moderately less decline; infusion reactions occurred in 26.4% and brain swelling or fluid on MRI in 12.6%, PubMed 36449413. ↩
20. Morris MC, Wang Y, Barnes LL, Bennett DA, Dawson-Hughes B, Booth SL. Nutrients and bioactives in green leafy vegetables and cognitive decline: prospective study. Neurology. 2018;90(3):e214-⁠e222. PubMed 29263222. In 960 older adults followed for a mean 4.7 years, those in the highest fifth of green leafy vegetable intake (median 1.3 servings a day) had a slower rate of cognitive decline, the equivalent of being 11 years younger in age; this is an observational association. ↩
21. Devore EE, Kang JH, Breteler MM, Grodstein F. Dietary intakes of berries and flavonoids in relation to cognitive decline. Ann Neurol. 2012;72(1):135-⁠143. PubMed 22535616. In 16,010 women aged 70 and older in the Nurses' Health Study, greater intakes of blueberries and strawberries were associated with slower rates of cognitive decline, an effect the authors estimated at up to 2.5 years of cognitive aging; this is an observational association. ↩
22. On omega-⁠3 and cognition: a Cochrane review of three randomized trials in 632 people with mild to moderate Alzheimer's disease found no benefit of omega-⁠3 supplements on cognition, daily function or dementia severity (high-quality evidence), PubMed 27063583, and an earlier Cochrane review of trials in cognitively healthy older people found no cognitive benefit either, PubMed 22696350. ↩
23. Gencer B, Djousse L, Al-Ramady OT, Cook NR, Manson JE, Albert CM. Effect of long-term marine omega-⁠3 fatty acids supplementation on the risk of atrial fibrillation in randomized controlled trials of cardiovascular outcomes: a systematic review and meta-analysis. Circulation. 2021;144(25):1981-⁠1990. PubMed 34612056. Seven trials with 81,210 people followed for about 5 years: omega-⁠3 supplements were linked to a higher risk of atrial fibrillation (hazard ratio 1.25), more so in trials of more than 1 g a day (1.49), and the risk rose with each additional gram. ↩
24. On curcumin: in a 24-⁠week randomized trial in 36 people with mild to moderate Alzheimer's disease, curcumin at 2 or 4 g a day showed no clinical or biomarker benefit over placebo, and blood levels stayed low, PubMed 23107780. ↩
25. On curcumin safety: NIH's complementary health center reports that liver damage has been reported in some people taking the more absorbable curcumin formulations, and advises stopping and seeing a clinician for tiredness, nausea, poor appetite, dark urine or yellowing of the skin, NCCIH, turmeric. ↩
26. On lion's mane: in a 16-⁠week placebo-controlled trial in 30 Japanese adults aged 50 to 80 with mild cognitive impairment, cognitive scores rose on the mushroom powder and fell again within 4 weeks of stopping; it has not been tested in large trials, PubMed 18844328. ↩
27. On treatment: the National Institute on Aging states that no known treatment ends Alzheimer's disease; that cholinesterase inhibitors are prescribed for mild to moderate symptoms and an NMDA antagonist for moderate to severe disease; that two anti-amyloid antibodies are approved in the United States for mild cognitive impairment or mild dementia due to Alzheimer's, after a PET scan or spinal fluid test confirms amyloid, and slowed decline in some trial participants over 18 months; that they can cause fluid buildup or bleeding in the brain, occasionally serious, so MRI monitoring is needed; and that medicines for behavior should be used only after non-drug approaches, NIA, how Alzheimer's disease is treated. ↩
28. On the course of the disease and care: NHS guidance states that symptoms progress slowly over several years at a different rate for each person; that memory problems can also be caused by depression, stress, medicines or other health problems; that anyone whose symptoms are rapidly getting worse should be seen by a doctor; that side effects of the symptom medicines, such as nausea, vomiting and loss of appetite, usually improve after 2 weeks; and that cognitive stimulation therapy, cognitive rehabilitation and reminiscence and life story work are part of care, NHS, Alzheimer's symptoms, NHS, Alzheimer's treatment. ↩
29. On emergencies: NHS guidance advises going to an emergency department or calling emergency services if someone suddenly becomes confused, since causes include infection, stroke and some prescription medicines, and calling emergency services after a fall with a possible head, back, neck or hip injury or when the person cannot get up; the CDC advises calling 911 at once for a drooping face, a drifting arm or slurred or strange speech, NHS, sudden confusion, NHS, falls, CDC, stroke signs. ↩
30. On getting lost: the National Institute on Aging advises that the person carries ID or a medical bracelet, that neighbors and local police know the person tends to wander, and that a recent photograph is kept to help police if the person becomes lost, NIA, wandering and getting lost. ↩
31. National Center for Complementary and Integrative Health (NIH), nccih.nih.gov, and the Linus Pauling Institute Micronutrient Information Center, lpi.oregonstate.edu/mic. ↩
32. On stress and the hippocampus: a 1998 study in Nature Neuroscience by Lupien and colleagues found that older adults whose cortisol, a stress hormone, stayed high over several years had a smaller hippocampus and poorer memory than those with normal cortisol, PubMed 10195112. ↩