Source: Alzheimer's & dementia : the journal of the Alzheimer's Association (2026)
A phase-II pilot trial gave older adults with early memory problems either nicotinamide riboside or a placebo for 12 weeks. Here's what the study measured, and what it did — and didn't — show.
Quick answer Nicotinamide riboside doubled blood NAD+ levels over 12 weeks, but produced no improvement in cognitive function, total cerebral blood flow, or blood pressure — the trial's own primary and secondary outcomes.
At a glance
- Design
- This is a randomised controlled trial, the strongest common design for testing whether a treatment works.
- Blinding & control
- Neither participants nor researchers knew who got the real treatment, and it was compared against a placebo — the strongest common protection against bias.
- Precision
- 42 participants — a small sample; individual results carry more weight than they should.
- Directness
- Outcomes measured: functional or performance measure.
- Independence
- Funding and conflicts of interest weren't reported — treat findings with extra caution.
- Reporting
- None of pre-registration, full-text availability, or primary-outcome significance reporting could be confirmed.
What did this study test, and why NR for memory concerns?
This was a phase-II, double-blind, randomised, placebo-controlled pilot study. It tested nicotinamide riboside (NR), a form of vitamin B3 that feeds into the NAD+ salvage pathway — the route the body uses to rebuild NAD+, a molecule cells need for energy metabolism and DNA repair. NAD+ is known to decline with age, which is the rationale for testing whether topping it up via NR has any effect on brain function.
The study ran for 12 weeks and compared an NR group against a placebo group. It sits at an early, exploratory stage of research — a pilot, not a large confirmatory trial — designed to check safety and gather preliminary signals rather than to settle the question definitively.
Who took part in the study?
Participants were older adults with amnestic mild cognitive impairment (aMCI), a diagnosis given when someone has noticeable memory problems that are more pronounced than typical for their age but don't yet meet the threshold for dementia. This is a group often studied as an early-warning population for later Alzheimer's-type decline.
Forty-two participants completed the study: 22 in the NR group and 20 on placebo. The paper's age range for participants was not reported in the source material, so it isn't possible to say how old, on average, this group was.
What was the study actually designed to measure?
The primary outcome was cognitive function — whether NR supplementation changed participants' scores on cognitive testing over the 12-week period. This is the measure the study was statistically built around, and the one its main conclusion rests on.
Secondary outcomes were total cerebral blood flow (CBF), a measure of how much blood reaches the brain overall, and blood pressure. Both are plausible pathways through which NAD+ changes might affect brain health, which is why they were tracked alongside cognition rather than instead of it.
How was the study structured to rule out bias?
It was randomised, meaning participants were allocated to NR or placebo by chance rather than choice, and double-blind, meaning neither participants nor the researchers assessing them knew who was taking which. Both features are designed to stop expectation — either the participant's or the researcher's — from colouring the results.
The study was also placebo-controlled, so any change in the NR group is judged against a comparison group given an inactive substitute rather than against no comparison at all. No trial registration ID was reported for this study in the source material.
What did this study report?
The results below cover the study's primary outcome (cognitive function), its two secondary outcomes (total cerebral blood flow and blood pressure), and two additional measures — blood NAD+ levels and a smaller, exploratory look at blood flow in specific brain regions.
- Blood NAD+ levels — increase: twofold increase. not reported Blood NAD+ increased twofold in the NR group
- Cognitive function (primary outcome) — no change. not reported No improvements in cognitive function
- Total cerebral blood flow (secondary outcome) — no change. not reported No improvements in total CBF
- Blood pressure (secondary outcome) — no change. not reported No improvements in blood pressure
- Regional cerebral blood flow (exploratory) — increase. not reported Exploratory analyses revealed potential increases in regional CBF, particularly in the hippocampus
What doesn't this study show?
Because this is a pilot study reported at abstract level, several things that a reader would normally want to weigh up simply aren't available. Here's what's missing from the picture.
- Does not report effects beyond 12 weeks
- Does not provide statistical significance values for reported outcomes
- Does not specify dose or regimen of NR used
What are this study's limitations?
The source material for this study did not list any limitations explicitly stated by the study's own authors.
Who funded this study, and is there a conflict of interest?
Neither funding sources nor conflicts of interest were reported in the source material available for this study, so no statement can be made about who paid for the research or whether the authors had any competing interests.
Funding: Not reported.
Conflicts of interest: Not reported.
What else do people ask about this study?
Did anyone in the study experience side effects?
No serious adverse effects were reported, and adherence — how consistently participants took their assigned supplement or placebo — was similar between the two groups.
What dose of NR was used in this trial?
The source material does not specify the dose or regimen used, so it isn't possible to say how much NR participants took or how often.
Is amnestic mild cognitive impairment the same as dementia?
No. Amnestic mild cognitive impairment describes memory difficulty that's greater than typical for someone's age but doesn't meet the criteria for a dementia diagnosis. It's often used in research as an early-stage population, precisely because not everyone with aMCI goes on to develop dementia.
Were the regional brain blood flow findings a reliable result?
They were described as exploratory, meaning this analysis wasn't part of the study's planned primary or secondary outcomes and should be read as a preliminary signal rather than a confirmed effect.
Was this a large, definitive trial?
No — it's described as a phase-II pilot study, a smaller, early-stage trial typically used to test safety and gather initial data ahead of any larger confirmatory research.
Where can you read the original study?
- Alzheimer's & dementia : the journal of the Alzheimer's Association (2026)
- DOI: 10.1002/alz.71605
- PMID: 42478598
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