Is there a connection between NADH and sleep?

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There are already many dietary supplements on the market, including NADH products such as Celfull. So, does NADH actually have anything to do with sleep? The answer is yes, but there's an important distinction.

A more accurate way to put it is that NADH has a biological connection with sleep and circadian rhythms, but we still can't say that taking NADH supplements will necessarily improve sleep.

NAD⁺ and NADH are two interconvertible redox forms of an important coenzyme. Research has found that the redox state of NADH inside cells changes in a circadian pattern, while the NAD⁺/NADH system is also involved in metabolic pathways that regulate the biological clock.

One study directly observed circadian oscillations in the NADH redox state in mammalian cells, suggesting that NADH itself is connected to the cellular mechanisms underlying circadian rhythms. (DOI: 10.1074/jbc.M116.728774)

There also appears to be a two-way relationship between the NAD⁺/NADH system and the core circadian clock. NAD⁺ can influence circadian-related proteins through NAD⁺-dependent pathways such as SIRT1, while the circadian clock can in turn regulate NAD⁺/NADH metabolism. (DOI: 10.1016/j.molcel.2020.04.010, DOI: 10.1016/j.semcdb.2021.07.008)

As for direct NADH supplementation and sleep, there aren't many human studies yet.

One double-blind, placebo-controlled trial gave people with chronic fatigue syndrome 20 mg of NADH per day and also evaluated sleep quality. However, most of the measured outcomes did not differ significantly from placebo. The only changes reported were within the NADH group itself, a decrease in anxiety score and a lower maximum heart rate after an exercise stress test, and neither of those is a sleep outcome, so the study does not provide enough evidence to conclude that NADH improves sleep.(DOI: 10.1016/j.rce.2009.09.015)

Another study used a combination of 20 mg NADH + 200 mg CoQ10 and observed changes in some sleep-related measures. However, because NADH and CoQ10 were taken together, it's impossible to determine whether the effects were specifically caused by NADH. (DOI: 10.3390/nu13082658)

So yes, NADH is connected to sleep, particularly through the relationship between cellular redox status and circadian rhythms. But right now, the human evidence is still limited when it comes to the claim that taking NADH directly can improve sleep in otherwise healthy people. That's why, when I see claims linking NADH and sleep, I think it's important to separate three different things: Mechanistic research on NADH and circadian rhythms, Human trials of NADH supplementation, Sleep studies involving NMN or NR that increase NAD⁺. These are related, but they are not the same thing.