NAD+ and Circadian Rhythms Are Deeply Linked in Dementia — Here's What We Know

Sleep and circadian rhythm disruptions are among the earliest and most pervasive features of dementia, yet the molecular mechanisms linking these disruptions to neurodegeneration remain incompletely understood. This 2026 review in Alzheimer's & Dementia, led by Zhang and colleagues from institutions across Norway, China, South Korea, and the USA, proposes that the progressive decline in NAD+ — a critical metabolic cofactor — and the breakdown of circadian rhythm architecture form a self-reinforcing cycle that accelerates cognitive deterioration across dementia subtypes.

The authors begin by mapping the molecular circadian clock, centered on the CLOCK-BMAL1 heterodimer that drives transcription of Period (PER) and Cryptochrome (CRY) genes via E-box elements, creating the ~24-hour transcription-translation feedback loop (TTFL). NAD+ intersects this system at multiple nodes. The rate-limiting NAD+ salvage enzyme NAMPT is itself a clock-controlled gene, creating a circadian oscillation in NAD+ availability. SIRT1, a NAD+-dependent deacetylase, deacetylates BMAL1 and PER proteins to regulate clock transcription. Conversely, PARP1 consumes NAD+ to ribosylate CLOCK, modulating its transcriptional output, while CD38 — a major NAD+-degrading enzyme — is transcriptionally regulated by the clock-controlled nuclear receptor REV-ERBα via NFIL3 suppression.

In dementia, this bidirectional coupling breaks down. NAD+ levels decline with aging and neurodegeneration due to reduced NAMPT activity, increased PARP1 activation (driven by oxidative stress and DNA damage), and elevated CD38 expression. Reduced NAD+ impairs SIRT1 activity, leading to hyperacetylation of BMAL1 and disrupted clock gene rhythmicity. Simultaneously, SCN neuronal loss weakens circadian output, reducing the amplitude of clock-driven NAMPT expression and further depleting NAD+. The review covers multiple dementia subtypes — Alzheimer's disease, Lewy body dementia, frontotemporal dementia, and vascular dementia — showing that circadian and sleep disturbances manifest differently across each but share common NAD+-related molecular vulnerabilities.

Therapeutically, the authors evaluate both pharmacological and lifestyle-based strategies. NAD+ precursors — nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) — have shown promise in preclinical models for restoring circadian amplitude and improving cognition, with several ongoing human clinical trials cited (NCT05040321, NCT04430517, NCT06971224, NCT05500170, NCT04070378). PARP1 inhibitors and CD38 inhibitors (e.g., apigenin, 78c) represent complementary approaches to reduce NAD+ drain. On the lifestyle side, timed bright-light exposure, structured aerobic exercise, and time-restricted eating can reinforce circadian entrainment and boost NAMPT activity, offering accessible, low-risk adjuncts to pharmacotherapy.

The review is careful to note that many proposed molecular interactions — particularly direct links between NAD+ signaling and specific TTFL components in human brain tissue — remain correlative or inferred from animal models. Causality in humans is largely unestablished. Nonetheless, the synthesis provides a detailed mechanistic framework and a compelling rationale for clinical trials targeting the NAD+-circadian axis in dementia prevention and treatment.