NAD+ and Brain Health: What the Science Actually Says About Aging, Neurodegeneration, and Cognitive Function

Key Takeaways 

• NAD+ is a vital molecule that powers mitochondrial energy production, DNA repair, and stress responses, which become more vulnerable as we age.
• NAD+ levels decline with age and with chronic inflammation and oxidative stress, making the brain less resilient and more susceptible to neurodegenerative diseases like Alzheimer’s and Parkinson’s.
• In preclinical models, restoring NAD+ consistently improves mitochondrial function, reduces oxidative and inflammatory stress, and protects neurons across conditions such as Alzheimer’s, Parkinson’s, mild cognitive impairment, and ataxia telangiectasia.
• Early human trials suggest precursors like niacin, NR, and NMN can safely boost NAD+ and improve brain‑related biomarkers, but we don’t yet see clear, consistent gains in cognition or disease progression.
• For now, NAD+ supplements are best seen as a long‑term brain support tool—not a “smart drug”—and should sit on top of foundational lifestyle habits like good sleep, movement, and metabolic health.

For some people, an aging brain might simply mean misplacing their car keys or fumbling for a word, but for others, it can mean losing the ability to manage daily tasks, remember loved ones, or live independently. As we get older, our brains do change, but whether your brain ages well or poorly can have a major impact on how you think, feel, and act—and what you do today can meaningfully shape your future cognition. 

As one of the most metabolically active organs in the body, the brain is uniquely vulnerable to age-related decline, combining a high demand for energy and healthy mitochondrial function with a very limited regenerative capacity.¹ This combination means that when cellular energy production or repair is disrupted, brain cells may be less able to bounce back, making problems with memory, thinking, and mood more likely over time. 

One key molecule involved in these processes is nicotinamide adenine dinucleotide (NAD+), a coenzyme central to cellular energy production and DNA repair, whose levels are known to decline with age. Researchers are now looking into how this drop affects brain health with age—and whether boosting NAD+ levels in the brain could help to support cognition. In this article, learn more about the link between NAD+ and brain health, what happens when NAD+ levels decline, and what the recent research on brain aging and neurological diseases does—and does not—support. 

How and Why NAD+ Levels Fall as the Brain Ages

NAD+ is essential for mitochondrial ATP production, and this matters especially in the brain,² which uses about a quarter of the body’s energy despite its size. Neurons are among the most energy‑hungry cells in the body and rely on ATP to maintain ion gradients, release neurotransmitters, and support fast, complex signaling.³

NAD+ also helps control how neurons respond to damage and stress over time⁴ by fueling sirtuins, a family of enzymes that help maintain healthy mitochondria, regulate inflammation, and support cellular stress responses, with neuroprotective effects on oxidative stress and toxic protein buildup.⁵

Another way that NAD+ supports brain health is by fueling poly(ADP-ribose) polymerases (PARPs), enzymes that help repair DNA damage. Neurons accumulate plenty of oxidative stress over a lifetime, and they have a limited capacity to replace themselves. PARPs rely on NAD+ to detect and repair this DNA damage, which helps to preserve the integrity of genetic material inside brain cells.⁶

Across the body—including the brain—NAD+ levels tend to decline with age, even in otherwise healthy people, with both human⁷ and animal⁴ studies showing lower NAD+ in older brains. Several overlapping processes that intensify as we grow older contribute to this decline, including rising oxidative stress, chronic low-grade inflammation, and growing demands on the DNA repair systems that all rely on NAD+.⁸ Aging is also often accompanied by chronic, low-grade inflammation and oxidative stress in the brain (and entire body).⁹ This inflammation can increase the activity of CD38, an enzyme that consumes NAD+.¹⁰ As CD38 becomes more active, it depletes NAD+ further, creating a feedback loop where inflammation and NAD+ loss reinforce each other over time.¹¹ This reduced ability to manage cellular stress is thought to contribute to the progression of neurological disorders, which we’ll explore in more detail in the following sections.

Overall, NAD+ is not just an “energy molecule.” It sits at the center of multiple systems that help neurons stay resilient and functional, including mitochondrial energy production, DNA repair, and cellular stress responses. Because it touches so many aspects of neuronal health, a decline in NAD+ can influence several upstream processes that shape how the brain ages. 

That said, this cycle is not inevitable, nor is it the same for everyone. Lifestyle factors like excessive alcohol use, poor sleep, chronic stress, and metabolic concerns (such as obesity or insulin resistance) can worsen oxidative stress and inflammation and accelerate NAD+ depletion.¹² Conversely, healthy nutrition and lifestyle habits can help maintain more favorable NAD+ stores,¹³ providing a tangible link between your daily choices and your brain’s overall resiliency. 

NAD+ and Neurodegeneration: What the Research Is Actually Showing

Much of what we know about NAD+ and neurodegeneration comes from animal and cell-based studies, with a small but growing number of human trials exploring this connection. While this is an active and promising area of research, it’s not settled science, and more work is needed to determine how NAD+ affects neurodegenerative disease development or progression. 

A central hypothesis is that restoring NAD+ with precursors like niacin, nicotinamide riboside (NR), or nicotinamide mononucleotide (NMN) may slow or buffer neurodegeneration by supporting the processes mentioned above: mitochondrial energy production, DNA repair, and cellular stress responses.¹⁴ Studies looking at dietary patterns in humans suggest that higher niacin intake is linked with better cognitive performance in older adults,¹⁵ offering epidemiological hints that NAD-related pathways may matter for brain function as we age.

More recently, a key foundational question in this area—whether these precursors actually raise NAD+ in the human brain—has begun to be answered. Studies in healthy adults have shown that supplemental NR increases brain NAD+ levels, providing proof-of-concept that oral precursors can reach and affect the brain.¹⁶'¹⁷ In the following sections, we’ll examine how NAD+ science is evolving in key neurological conditions, including Alzheimer’s and Parkinson’s disease, ataxia telangiectasia, dementia, and mild cognitive impairment. Detailed summaries of all studies discussed in this section are provided in the Appendix.

NAD+ and Alzheimer’s Disease

Alzheimer’s disease (AD) is the most common cause of dementia, affecting over 7 million Americans and leading to characteristic symptoms like progressive memory loss and thinking changes. In the brain, hallmark changes in AD include a buildup of amyloid‑β plaques, tau tangles, mitochondrial dysfunction, and chronic inflammation.¹⁸ One proposed link between NAD+ and these brain changes involves PARP overactivation, as amyloid-induced DNA damage can activate PARP1.¹⁹ This consumes NAD+ in the process of repairing damaged DNA and may contribute to that damaging cycle of NAD+ depletion and impaired repair capacity. 

In preclinical models of AD, boosting NAD+ has led to improvements like reductions in amyloid and tau pathology,²⁰ improvements in synaptic function and plasticity,²¹ and better performance on learning and memory tasks.²¹ While these studies in animals and cell models are promising and have generated clinical interest, human trials in people with or at risk for AD remain limited, and the available studies show mixed results.

For example, in a randomized, placebo-controlled, phase II proof-of-concept trial, high-dose nicotinamide did not significantly change plasma pTau231—an Alzheimer’s biomarker—over 24 weeks in people with early symptomatic disease.²² However, other trials looking at AD-related biomarkers in the brain have supported the idea that NR can benefit neuronal NAD-related pathways. One study looked at biomarkers in plasma extracellular vesicles enriched for neuronal origin (NEVs) from healthy older adults, finding that oral NR increased NAD+ in these vesicles and lowered biomarkers linked to neurodegenerative and neuroinflammatory pathways.²³ Similarly, another study showed that older adults with subjective cognitive decline or mild cognitive impairment who supplemented with 1000 mg NR daily for 8 weeks safely lowered plasma pTau217—a blood biomarker linked to Alzheimer’s pathology—versus placebo, although it did not improve standard cognitive tests or other plasma biomarkers.²⁴'²⁵

Taken together, these findings suggest that while NAD‑targeted therapies show encouraging biomarker and mechanistic signals in Alzheimer’s, it is still too early to conclude that they meaningfully slow or prevent cognitive decline in people.

NAD+ and Mild Cognitive Impairment (MCI) and Dementia

Mild cognitive impairment (MCI) is often described as a transitional state between typical age-related forgetfulness and dementia, when measurable problems with memory or thinking are present but daily independence is largely preserved. In contrast, subjective cognitive decline (SCD) is a self-reported experience of worsening memory or thinking without seeing objective deficits on tests. Together, both MCI and SCD can be seen as early warning signs for AD, and both represent a potential window for early intervention.

Researchers are interested in NAD+ therapies at these earlier stages because NAD+ decline, mitochondrial dysfunction, oxidative stress, and impaired DNA repair are thought to begin years before dementia symptoms appear, making earlier intervention potentially more effective.²⁶ In preclinical models that mimic early cognitive decline, supplementing with NAD+ injections or precursors like NR or NMN has been shown to support mitochondrial function, reduce markers of neuroinflammation and oxidative stress, and improve learning and memory.²⁷'²⁸

In humans, the evidence is still emerging. In the previously mentioned study of older adults with MCI or SCD, NR was found to be safe and produced promising effects on blood and plasma biomarkers of AD, including reduced pTau217, but did not improve standard neuropsychological test scores over the short trial period.²⁴ A separate pilot trial in MCI similarly found that NR safely increased blood NAD+ without measurable cognitive benefits.²⁹ This early work suggests that, in MCI and SCD, NAD+ therapies are best considered experimental approaches that may help support at‑risk brain biology, rather than established treatments for improving day‑to‑day thinking or memory.

NAD+ and Ataxia Telangiectasia

Ataxia telangiectasia (AT) is a rare, inherited neurodegenerative disorder caused by mutations in the ATM gene, which plays a key role in detecting DNA damage and coordinating DNA repair.³⁰ Because AT is fundamentally a DNA repair disorder, it provides a direct example of how impaired DNA repair, PARP activity, and NAD+ depletion can interact in the nervous system.

In preclinical AT models, boosting NAD+ with precursors like NR and NMN improves mitochondrial function, stimulates mitophagy, reduces DNA damage signaling and neuroinflammation, and delays memory loss while improving coordination and extending lifespan.³¹'³² Clinical work in people with AT points in a similar direction, with studies in children and adults with AT showing that NR supplementation raised blood NAD+ levels, improved motor coordination and eye movement, and reduced symptoms of ataxia.³³'³⁴ While promising, controlled, longer-term trials are still needed to confirm these disease‑modifying effects.

NAD+ and Parkinson’s Disease

Parkinson’s disease (PD) is a progressive neurodegenerative disorder and the second most common of its kind worldwide, characterized by the loss of dopamine-producing neurons in the substantia nigra of the brain and the presence of Lewy bodies, or abnormal aggregates of the protein α‑synuclein. Clinically, PD is best known for motor symptoms like slowness of movement (bradykinesia), tremor, and rigidity, but it also brings non‑motor issues such as cognitive decline, sleep disturbances, and mood changes that can be equally disruptive to daily life.

PD currently has the largest body of human NAD+ research of any neurological condition, in part because mitochondrial dysfunction in dopaminergic neurons is central to its biology.³⁵ These neurons have high energy demands and are especially vulnerable when mitochondrial function declines,³⁶ so NAD+ has emerged as a particularly relevant target in PD.

Preclinical research has laid the groundwork for this theory. Across a wide range of models—spanning cultured neurons,³⁷ fruit flies,³⁸ zebrafish,³⁹ worms,⁴⁰ and mice⁴⁰—studies show that NAD+ precursors can prevent or improve several aspects of PD‑like pathology, including impaired mitochondrial function and mitophagy, heightened neuroinflammation and oxidative stress, loss of dopaminergic neurons, and motor deficits on behavioral tests. Epidemiologically, large NHANES analyses of over 20,000 U.S. adults have also found that higher dietary niacin intake is associated with lower PD risk, providing an early, real‑world signal that NAD+‑related pathways may matter for PD development.⁴¹

Clinically, niacin and NR have both been studied as NAD+‑targeted strategies in PD. Small trials of niacin in people with PD suggest it is generally safe and may modestly improve motor function, fatigue, or quality‑of‑life measures,⁴² potentially through replenishing NAD+ via the Preiss–Handler pathway and modulating neuroinflammation via the GPR109A receptor, though results remain preliminary.⁴³ NR has been shown in the NADPARK and related studies to efficiently raise NAD+ in blood and brain, support mitochondrial function, and produce early signals of benefit on motor and cognitive measures, but these phase I/II trials are small and not yet definitive.⁴⁴'⁴⁵ 

Can Boosting NAD+ Improve Your Cognition and Focus? What the Evidence Says

Many people supplement with NR, NMN, or other NAD+ precursors with the goal of sharper thinking, better focus, or mental clarity—and that interest is understandable, given how central NAD+ is to brain energy metabolism and cellular repair. In theory, improving mitochondrial function and reducing neuroinflammation could help support cognitive performance, as neurons depend on efficient energy production and controlled inflammatory signaling to function properly.³

That said, clinical evidence that NAD+ precursors enhance cognition, focus, or mental clarity in healthy humans is very limited. Most of the stronger rationale for NAD+ comes from preclinical neuroprotection and from early clinical work in disease contexts (such as MCI, PD, or AT), where the goal is to preserve function or slow decline rather than boost normal performance above baseline.²⁸

In long COVID, for example, a recent randomized trial found that NR safely raised NAD+ and improved self‑reported symptoms like fatigue, sleep, and mood, but it did not outperform placebo on objective cognitive tests or “brain fog” measures—highlighting both the modest effects seen so far and the difficulty of capturing a subjective symptom like brain fog with standard cognitive testing

Overall, while the underlying biology behind NAD+ and brain function makes the idea of better cognition or mental clarity plausible, the current human data does not justify treating NAD+ precursors as “smart drugs” or brain boosters for healthy people. However, the absence of evidence is not the same as evidence of absence, and this remains an active area of research. Larger, longer trials in the future may clarify whether subtle cognitive benefits exist. Still, based on what we know today, NAD+ supplementation should be viewed primarily as a potential tool for supporting brain health and resilience over time, not as a guaranteed way to sharpen focus or mental clarity in the short term.

The Bottom Line: What NAD+ Research Means for Brain Health Today

There’s no doubt that NAD+ matters for brain health—it fuels mitochondrial energy production, supports DNA repair, and coordinates stress responses in neurons, all of which become more vulnerable as NAD+ levels drop with age. With declining NAD+ levels, the brain is left with less energetic and repair capacity, combined with rising oxidative stress, inflammation, and DNA damage, ultimately creating neurological vulnerability. 

Across conditions like Alzheimer’s disease, Parkinson’s disease, mild cognitive impairment, and ataxia telangiectasia, preclinical studies show that restoring NAD+ often improves mitochondrial function, reduces oxidative and inflammatory stress, supports DNA repair, and can preserve neuronal structure and function in animal and cell models. That said, human studies with NAD+ precursors like NR, NMN, and niacin are still in the early stages. Some are encouraging in places, especially around biomarkers, but not yet definitive in terms of slowing disease progression or improving cognition in large, long-term trials.

Overall, the case for NAD+ in brain health has solid biological mechanisms and strong preclinical data, while human evidence is still catching up. Larger, longer, and more rigorous clinical trials focused on outcomes like cognition, function, and disease progression will be crucial to determine whether NAD+‑targeted strategies truly translate into meaningful benefits for people.

Appendix

Table 1. NAD+ Precursor Clinical Studies: Brain Health and Neurological Disease

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