What recent studies reveal about memory, diet, and brain aging - critical summary review

What scientists measure when they talk about brain aging

There is no way to watch a brain grow old from the outside, so researchers work with a small set of stand-ins, followed over years.

The first is the white matter, made up mainly of the nerve fibres that connect different regions of the brain. Those connections let brain areas exchange information and take part in functions such as memory, attention and movement. On magnetic resonance scans, small areas of that tissue can appear brighter than the rest. They are called white matter hyperintensities, they become common with age, and they can be related to changes in the brain's small blood vessels and to damage in nerve fibres. On their own, they do not mean a person has dementia or will develop Alzheimer's. What carries weight is how much there is and how fast it piles up: a larger volume, accumulating over the years, is associated with worse brain health and can come alongside memory and cognitive problems.

The second stand-in is performance on repeated cognitive tests, which separate attention, memory, executive function and language instead of producing one single score. The third is genetics, and in particular the apolipoprotein E gene, whose variant known as APOE ε4 is the strongest common genetic risk factor for Alzheimer's disease. The fourth is biological age estimated from epigenetic markers, which can come out below the age written on someone's documents.

That is the vocabulary behind a cluster of findings that reached the public almost at the same time in recent days, each one picking a different factor and asking what it does to the brain. Almost none of them can show cause and effect.

Early menopause joins the list of hormonal factors

A study published in August in the journal JAMA Network Open followed 2,603 women for up to 18 years and found an association between the age at which menopause happened and later changes in the structure and function of the brain. The data come from two long-running projects on aging and cognition, the Religious Orders Study and the Rush Memory and Aging Project, and part of the group had repeat scans, which let researchers see how the tissue changed over time.

Among women who went through spontaneous menopause, meaning it occurred naturally rather than being caused by treatment or surgery, a five-year difference in the age it happened was associated with about 15% more volume of white matter hyperintensities over a decade. The earlier the menopause, the faster those alterations accumulated. The association held after the researchers took into account age, schooling, blood pressure, body mass index and other health factors.

Cognition moved in the same direction. Women who reached menopause earlier declined faster on global cognition and especially on episodic memory, the kind used to recall events and personal experiences. There was also an association with the age of Alzheimer's diagnosis: in the model used, a ten-year difference in the age of menopause corresponded to roughly 1.8 fewer years until diagnosis. The mean age of diagnosis among participants was 88.4 years.

The two subgroups did not behave the same way. The accumulation of white matter alterations was clearest among women with spontaneous menopause, while the associations with cognitive decline and with time to diagnosis were more pronounced among those who had surgical menopause.

The authors stress that the work is observational and does not establish cause and effect. One hypothesis raised is estrogen, produced in progressively smaller amounts by the ovaries during menopause and involved in brain function, energy metabolism and the regulation of inflammation. Another is the reverse framing: a faster biological aging process could lie behind both an earlier menopause and the later brain changes. Menopause age was self-reported, and the study cannot say whether delaying menopause or changing hormone levels would prevent anything.

A poor diet seemed to weigh only on carriers of the risk gene

A study published recently in the journal Nutrients used data from the Western Australia Memory Study, which followed 185 older adults in Perth for more than seven years. Researchers at Murdoch University and Alzheimer's Research Australia sorted participants' diets into two patterns: a western one, with red and processed meats, snacks, pizza, sweets, refined grains and beer, and a prudent one, with fruit, vegetables, garlic and whole grains. Nobody had a dementia diagnosis on entry, and everyone was tested for genetic susceptibility.

Among carriers of the APOE ε4 variant, greater adherence to the western pattern was associated with faster decline in attention. Lead author Carolina Blagojevic Castro said in a statement that no significant associations appeared between the prudent pattern and decline, nor between the western pattern and decline in people who were not ε4 carriers. Diet is an attractive target because it can often be changed easily, she said, but people may not react the same way to the same pattern. The study is observational, and she stressed that more research is needed before the findings can be turned into dietary recommendations based on genetic risk.

A separate paper, in the journal PLOS One, points in a similar direction with a different nutrient. Japanese scientists analysed scans and blood levels of vitamin C in 2,044 older adults and found a link between the nutrient and greater structural integrity and better neuronal functioning. It is a cross-sectional study, a snapshot of one moment, useful for forming hypotheses rather than proving them. Celso Cukier, a nutrologist at Einstein Hospital Israelita, told Folha de S.Paulo that part of the participants probably already had a healthy lifestyle and a balanced diet, and that the result does not support taking vitamin C supplements for the brain. His recommendation is a diet rich in fruit, vegetables and grains.

Bones and brain: an unexpected link with osteoporosis drugs

A study published in the journal Alzheimer's & Dementia looked at 121,492 adults aged 60 or over in Hong Kong, all recently diagnosed with osteoporosis or having suffered a serious fracture of the spine, humerus, wrist or hip, and none previously treated for bone loss. Those who used nitrogen-containing bisphosphonates, a class of medicines that slows bone loss and includes alendronate, ibandronate, risedronate and zoledronate, had a 16% lower risk of developing Alzheimer's and related dementias than people who took no osteoporosis medication.

Study author Ching-Lung Cheung, of the University of Hong Kong, told Fox News Digital that emerging evidence points to a bone-brain axis, and that earlier work had already found people with low bone mass to be more likely to develop dementia later in life. He also set out the limits: the design is observational, so the findings do not prove that the medication reduces dementia risk, and the next step is confirmation in a clinical trial. The study involved only a Chinese population, there was no baseline cognitive testing, and factors such as schooling, social isolation, air pollution and vision loss could also have affected the results. According to the authors, the findings do not yet justify prescribing bisphosphonates to prevent or treat dementia.

A body that lived 117 years, worn and protected at once

The Spaniard Maria Branyas died at 117 in August 2024, and an analysis of her organism by researchers at the Josep Carreras Leukaemia Research Institute was published in the journal Cell Reports Medicine in October 2025. It found signs typical of extreme aging, including very short telomeres, inflammation in the immune system and aged defence cells, and at the same time low overall inflammation levels, a gut microbiome dominated by bacteria considered beneficial, and markers associated with protection of the brain and the heart. Her biological age estimated from epigenetic markers came out below her chronological age.

For the researchers, the picture shows that different parts of the same organism can age at different rates. They also note that her longevity cannot be attributed to specific habits: diet, social relationships and the absence of risky behaviour are listed only as possible factors.

What already appears to help

While the associations pile up, the part that gets treated as settled enough to organise services around is prevention and care. On 19 September, a free event at the Bunkyo building in Liberdade, in central São Paulo, with online participation, puts that agenda in one room: advances in Alzheimer's diagnosis, prevention through physical activity, food, sleep, social life, learning and intellectual stimulation, and a session on cognitive stimulation used by carers and as part of the treatment of people already diagnosed with dementia. Celene Pinheiro, a geriatrician and president of the Brazilian Alzheimer's Association, closes the programme with the actress Beth Goulart in a panel on life after a dementia diagnosis. The event also discusses public policy, including Brazil's National Policy for Integral Care of People with Alzheimer's Disease and Other Dementias and the National Dementia Plan, and the case of Volta Redonda, in Rio de Janeiro state, which runs a public day centre for older people with Alzheimer's and support for their families.

Erica Oliveira, a specialist in cognitive stimulation quoted in a sponsored article published on the O Globo website, says activities that challenge memory, attention, reasoning and problem-solving help build and maintain cognitive reserve, and that this stimulation should be combined with regular physical activity, adequate sleep, a balanced diet and active social relationships.

What to do with this information

The first move is not to swap habits because of one headline. Every finding above comes from observational work, and in each case the researchers themselves said so: the menopause study cannot establish cause and effect, the diet paper is not yet enough to support recommendations by genetic risk, the vitamin C paper is a snapshot, and the bisphosphonate authors say a clinical trial is the next step.

The second is that the same factor does not land the same way on everyone. A western diet was linked to faster decline in attention only among APOE ε4 carriers. The brain imaging association was clearest in women with spontaneous menopause, while the cognitive ones were stronger after surgical menopause. That is the practical reason these papers work better as context in a consultation than as instructions. Someone with a family history of Alzheimer's, someone who went through menopause early or after surgery, and someone already taking medication for osteoporosis all have concrete reasons to mention them to a doctor, and none of them has grounds to start or stop a treatment because of an association.

For everyone else, what the studies actually sustain is the unglamorous combination: a varied diet rich in fruit, vegetables and grains rather than an isolated supplement, regular cognitive stimulation, sleep, exercise and social life. And the thing worth watching from here is whether any of these associations survives the move into clinical trials, which is where an association stops being a correlation and starts being a treatment.