Kidney health, blood pressure and brain ageing: what the evidence connects

Text written with the help of AI.

A kidney test and a blood-pressure reading can both be relevant to brain ageing, but they answer different questions. Kidney studies have found associations with dementia; blood-pressure trials have tested whether treatment changes cognitive outcomes. Keeping those findings separate prevents a useful health marker from becoming a prediction about your memory.

What kidney results can tell you

Blood pressure and kidney function affect each other. High blood pressure can damage kidney blood vessels, while impaired kidneys can retain fluid and raise blood pressure further. NIDDK, 2020.

Two tests capture different aspects of kidney health. Estimated glomerular filtration rate (eGFR) estimates filtration from a blood sample. Urine albumin-to-creatinine ratio (UACR) measures albumin relative to creatinine in urine; increased albumin can indicate kidney damage. The tests complement each other. NIDDK, 2016.

In the US Atherosclerosis Risk in Communities study, researchers examined kidney measurements in nearly 10,000 adults aged 54 to 74, with a later assessment in older participants. Higher urine albumin was associated with subsequent dementia. Associations involving eGFR, however, depended on how filtration was estimated: estimates using cystatin C or another protein showed associations that creatinine-based estimates did not. ARIC investigators, 2020.

That difference makes a single kidney number a poor cognitive forecast. The study followed people over time; it did not test whether treating kidney disease prevents dementia. Nor does the association establish that lowering urine albumin preserves memory.

What blood-pressure treatment has shown

For hypertension, there is stronger evidence about intervention. In a trial involving 33,995 adults aged 40 and over with uncontrolled hypertension in rural China, villages were assigned to structured treatment or usual care. Community healthcare providers adjusted medicines under physician supervision. After four years, the intervention group had a reported 15% lower relative risk of all-cause dementia. That is neither a 15-percentage-point reduction nor a promise of benefit for any one person. The trial does not show that people with normal blood pressure should lower it further. China Rural Hypertension Control Project, 2025.

Other trials set limits on the interpretation. Extended follow-up from SPRINT found fewer cases of mild cognitive impairment with intensive blood-pressure treatment, while the result for probable dementia alone remained statistically inconclusive. Its participants had hypertension and increased cardiovascular risk; people with diabetes or previous stroke were excluded. SPRINT investigators, 2025.

In an analysis from China's ESPRIT trial, targeting systolic pressure below 120 rather than below 140 mmHg did not significantly improve average scores on a general cognitive screening test over a median 3.4 years. There were too few dementia cases to draw a useful conclusion about that outcome. Wang and colleagues, 2026.

Dementia diagnoses, mild cognitive impairment and screening scores are different outcomes. Taken together, these trials support treating hypertension seriously, while leaving the right target and likely cognitive benefit to be judged in the context of an individual's health.

Why bicarbonate does not follow from either finding

Sodium bicarbonate is sometimes used to address metabolic acidosis in people with chronic kidney disease. Its effects in that setting cannot be assumed to extend to healthy adults or to dementia prevention.

The Italian UBI trial compared bicarbonate with standard care in 740 people with chronic kidney disease and metabolic acidosis. Its primary endpoint was doubling of serum creatinine, not kidney failure or cognitive decline. The trial also reported dialysis initiation separately. Because it was open-label, participants and clinicians knew which treatment was given. UBI investigators, 2019.

The double-blind UK BiCARB trial compared bicarbonate with placebo in 300 older adults with advanced chronic kidney disease and low bicarbonate levels. It found no significant improvement in physical function or kidney filtration and recorded more adverse events in the bicarbonate group. The two trials studied different populations and protocols, so neither settles every question about clinical use. Neither tested whether bicarbonate protects memory. BiCARB study group, 2020.

KDIGO's kidney guideline treats acidosis management as a monitored clinical decision, including attention to blood pressure, potassium and fluid status. These findings offer no basis for taking bicarbonate to protect cognition. KDIGO, 2024.

Read the pattern before changing anything

For people at risk of chronic kidney disease, KDIGO recommends assessing both urine albumin and filtration. A single abnormal result does not establish chronic kidney disease: chronicity requires evidence extending over at least three months. Previous results and their dates therefore matter when discussing a new finding. KDIGO, 2024.

Personal impressions belong in a different category from these measurements. Feeling more alert after a change in routine cannot demonstrate improved filtration or reduced dementia risk. The useful next step is to understand existing blood-pressure and kidney results and whether follow-up is warranted. These studies do not justify changing prescribed blood-pressure treatment yourself.

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