If you are worried about your memory, or you have noticed changes in someone you love, you are asking one of the most important questions in brain health. The short answer: a brain scan can help a clinician rule out other causes and look for changes in the brain, but no single scan confirms Alzheimer’s on its own.
What early research says about brain changes and scans
The NIA says changes in the brain occur many years before the first symptoms of Alzheimer’s disease appear. Research on using scans to spot those changes is still early: a 2026 Nature Aging study proposes predicting diagnosis and cognitive scores from a single MRI scan, and that approach remains research. The NIA (page reviewed October 2023) says researchers have identified promising prevention strategies and are still learning what might and might not work (NIA on preventing Alzheimer’s).
The wider research agrees that brain changes start early. The NIA notes that brain changes occur many years before the first symptoms, which points to a possible window of opportunity, but that nothing has been proven yet to prevent Alzheimer’s. A 2024 study in PLoS One describes the same timeline: the disease can stay without symptoms for decades while amyloid and tau keep building (2024 PLoS One PET pattern study).
Can Alzheimer’s be diagnosed with a brain scan?
Not on its own. UK GP guidance on Alzheimer’s diagnosis, the ‘Alzheimer’s disease – Diagnosis’ page reviewed in July 2024, says there is no simple and reliable test for Alzheimer’s, and that cognitive tests should never be used by themselves to diagnose dementia. It is UK guidance, so check with your own clinician how it applies to you. A GP usually checks for other causes first, including depression, stress, medicines, alcohol, hormone problems and nutrient deficiencies, and may order blood tests for the same reason. Blood tests you are offered usually rule out other causes; ask your clinician whether a test aimed at Alzheimer’s itself is an option for you. If a specialist wants more, they may recommend a CT or MRI scan to rule out other conditions and look for signs of damage linked to Alzheimer’s.
The Lewy Body Dementia Association makes the same point about scans: CT and MRI are not diagnostic of Lewy body dementia, but they help a physician. If you are unsure whether a change needs a visit, the NIA guidance on memory problems lists signs that mean it is time to talk with a doctor, such as getting lost in places you know well or becoming more confused about time, people and places.
PET scans: what the pictures show and how accurate they are
A PET scan uses a small amount of radioactive tracer and a special camera. Areas that take up more of the tracer show as brighter, and areas that take up less show as darker. The Lewy Body Dementia Association’s imaging article notes that FDG PET shows less metabolism in the posterior parietal lobe, a region toward the back of the brain, in both Alzheimer’s and Lewy body dementia. Amyloid PET looks for the protein that builds up in Alzheimer’s. According to the same article, PIB amyloid PET cannot separate Alzheimer’s from Lewy body dementia by itself, and PIB amyloid imaging is described as a research tool.
On accuracy, the figures belong in each study’s full paper, not in a headline. Ask the clinic which scan they plan to use and where its published accuracy numbers are, and read them before you decide what a result means.
Which brain scan tests exist, and what each can tell you
| Test | What it shows | Limits |
|---|---|---|
| CT scan | Several X-ray images combined into a picture of the brain. Shows strokes, tumors, head injury and other structural changes, including hydrocephalus | Not diagnostic of Lewy body dementia; helps detect structural causes such as strokes and tumors |
| MRI | Detailed images of brain size and shape. Gives clearer structural images than CT and can show the shrinkage typical of degenerative dementia | Cannot distinguish Alzheimer’s from Lewy body dementia; mainly helps rule out other causes |
| Standard PET (glucose use) | How well brain cells use sugar, measured with a tracer. The Lewy Body Dementia Association says it is available as a diagnostic tool in the U.S.; check with Medicare or your plan about coverage | Less metabolism in the parietal lobe appears in both Alzheimer’s and Lewy body dementia |
| Amyloid PET | Amyloid protein, which builds up in Alzheimer’s and is also found in Lewy body dementia | Cannot separate the two by itself (PIB); PIB is described as a research tool |
| DAT scan | Changes in the dopamine transporter, used to help tell Lewy body dementia from Alzheimer’s | The LBDA article says it was approved for use in the U.S. |
| Blood tests | Part of the GP workup to rule out other causes of memory changes | Ask your clinician whether an Alzheimer’s-specific blood test is an option for you |
| Specialist memory tests | Pen-and-paper tasks for memory, attention, language, time and place | Scores can be affected by education, and they are never used alone |
What the research says about risk and prevention
A 2024 eLife study tested many traits against Alzheimer’s risk using large biobank data. It found 48 significant associations, and reported that family history, high cholesterol, and traits related to intelligence and education were strongly and independently associated with Alzheimer’s (2024 eLife risk factor study). These are associations, not proof of cause, and they do not tell you what your own risk is.
A 2026 Nature Aging study proposes predicting diagnosis and cognitive scores from a single MRI scan. Its abstract presents this as a proposed approach for early diagnosis and clinical trial design, which is still research (2026 Nature Aging MRI study).
For prevention, the NIA describes a 2017 review by the National Academies of Sciences, Engineering, and Medicine that found “encouraging but inconclusive” evidence for three approaches: blood pressure management, increased physical activity and cognitive training. In the SPRINT-MIND trial, lowering systolic blood pressure to below 120 mmHg, rather than the standard 140, significantly reduced the risk of mild cognitive impairment. Your clinician decides which target fits you.
Cognitive training has some support. NIA reports that in the ACTIVE trial, reasoning and speed-of-processing training led to less decline, with gains lasting up to 10 years. A separate analysis of 215 trials found that training in several areas also improved some untrained skills. The long-term benefit for independent living is unknown. NIA says there is currently not enough evidence that commercial computer-based brain-training apps have the same impact. When a product claims to help memory, the FTC health products compliance guidance says such claims need competent and reliable scientific evidence behind them.
Your options side by side
Here is how the main routes compare. Only a clinician who knows your history can help you choose among them. For the supplements, the NCCIH ginkgo overview and the NIH omega-3 fact sheet have the detail.
| Option | What the research shows | Cost | Who it suits | Limits |
|---|---|---|---|---|
| GP and memory clinic assessment | Standard first step: questions, tests, possibly CT or MRI, and blood tests to rule out other causes | Ask your insurer or clinic | Anyone worried about memory or thinking | Does not confirm Alzheimer’s on its own |
| Approved Alzheimer’s drugs | Eligibility is decided case by case by a specialist | Check your drug plan and the clinic | People a specialist finds eligible | Needs specialist assessment and follow-up |
| Clinical trials | NIA says research volunteers are needed for studies of diagnosis, treatment and prevention | Ask the trial team | People willing to join research | Taking part does not guarantee a benefit |
| Exercise and blood pressure control | The 2017 review found encouraging but inconclusive evidence for blood pressure management, physical activity and cognitive training; SPRINT-MIND found lower blood pressure reduced MCI risk | Costs vary; ask your clinician | Most adults; NIA advises checking with a provider before starting vigorous exercise | Not proven to prevent Alzheimer’s |
| Structured cognitive training | ACTIVE trial improved the skills trained, and reasoning and speed-of-processing gains lasted up to 10 years | Varies by program | People who want structured practice | Long-term benefit for independent living is unknown; commercial brain-training apps lack the same evidence |
| Ginkgo supplements | In a large trial of more than 3,000 people for a median of 6 years, ginkgo did not reduce dementia rates; NCCIH says it has not been shown to prevent or slow dementia | Check the label and price where you buy | People considering supplements, after talking with a clinician | Can increase bleeding risk with anticoagulants such as warfarin |
| Omega-3 supplements | Some research links omega-3s from food with lower risk; more study is needed | Check the label and price where you buy | People considering supplements, after talking with a clinician | High doses can cause bleeding problems with warfarin; side effects are usually mild |
| Daily multivitamin | NIA says recent trials showed a daily multivitamin may improve memory and cognition in older adults | Check the label and price where you buy | Older adults discussing options with a clinician | NIA says no vitamin or supplement is recommended for preventing Alzheimer’s |
Approved drugs, clinical trials and the cost question
Whether an approved Alzheimer’s drug suits you is a specialist’s decision, based on your eligibility. Ask the specialist which drug they would consider, what it requires, and what it would cost you. Prices and coverage change, so check current costs with your insurer, your drug plan and the clinic. Alzheimer’s drug cost and monitoring walks through what to add to your total.
If you want to explore studies, NIA says volunteers are needed for trials on diagnosis, treatment and prevention, and the Alzheimers.gov Clinical Trials Finder lists study sites near you.
Types of dementia
Dementia is not a normal part of aging, according to the NIA. The main types it lists are Alzheimer’s disease, Lewy body dementia, frontotemporal dementia and vascular dementia, and symptoms vary from person to person. Vascular dementia is linked to damage from stroke, which the NIA says can damage blood vessels in the brain.
Caregiving, services and money questions
For tips on caring for a family member, the NIA’s ADEAR Center offers publications for families and caregivers, and its staff make referrals to local and national resources. Call 800-438-4380 or write to adear@nia.nih.gov. The Alzheimer’s Association helpline is 800-272-3900, and the Eldercare Locator at 800-677-1116 can point you to local help with care and services.
On protecting assets, the answer depends on your state and your husband’s diagnosis, so talk with an elder law attorney, who can give you legal information for your situation. This is general information, not legal advice. On when someone should move into care and how a marriage changes, ask your husband’s clinician and the memory clinic team, and use the Eldercare Locator line for local options.
Before you decide: questions for your clinician
- Which tests do you recommend, and what will each one tell you that the others cannot?
- Which scan do you plan to use, and where are its published accuracy numbers?
- Am I a candidate for an approved drug or a clinical trial, and what would each cost me?
- Which of my medicines or supplements could affect bleeding or memory?
- What should I track between visits, and when should I call?
Take one small step this week: write down the changes you have noticed, with rough dates, and book a visit with your GP. Our memory and brain fog page is a useful companion read as you prepare.
By the Global MH Summit Research Team
This article is for general information purposes only and does not constitute medical advice. Consult your doctor or qualified healthcare provider before making changes to your health routine.