In every U.S. state, somewhere between three and five in ten adults report sleeping less than the seven hours per night that health authorities recommend. According to the Centers for Disease Control and Prevention's 2022 state-level data, the share of adults reporting insufficient sleep ranged from 30 percent in Vermont to 46 percent in Hawaii. The CDC also notes that the national picture barely moved between 2013 and 2022, despite a decade of sleep apps, wearables and public awareness campaigns.
That persistent sleep gap has turned the science of circadian rhythm into one of the most closely watched areas of health research. One thread of that work has drawn particular public interest: the relationship between the body's internal clock and NAD+, a coenzyme central to cellular metabolism. As NAD+ injection therapy becomes more visible in the wellness market, it is worth understanding what scientists are actually studying, and what remains unanswered.
The scale of the sleep problem
Sleep debt is not distributed evenly. The CDC's 2022 data show that adults aged 45 to 64 had among the highest rates of insufficient sleep, at 39 percent, and that men (37 percent) were more likely than women to report short sleep. Native Hawaiian or Pacific Islander adults reported the highest rate of any group, at 49 percent.
Those numbers matter because sleep is not an isolated behavior. Researchers have connected chronic short sleep with metabolic, cardiovascular and mental health concerns, and the CDC has long treated insufficient sleep as a public health issue rather than a lifestyle quirk. The 45-to-64 age band is especially notable: it overlaps with the years in which many adults first begin thinking seriously about healthy aging.
A clock in every cell
The modern understanding of circadian rhythm was recognized at the highest level in 2017, when the Nobel Prize in Physiology or Medicine was awarded to Jeffrey Hall, Michael Rosbash and Michael Young for discovering the molecular mechanisms that control circadian rhythms. Their work, initially in fruit flies, showed that a set of genes and proteins form a feedback loop that oscillates on a roughly 24-hour cycle.
In mammals, a "master clock" in the brain's suprachiasmatic nucleus responds to light and coordinates timing across the body. But nearly every tissue, including the liver, muscle, and fat, also contains its own peripheral clock built from core clock proteins such as CLOCK and BMAL1. These peripheral clocks help align metabolism with daily patterns of eating, activity and rest.
Where NAD+ enters the picture
Nicotinamide adenine dinucleotide, or NAD+, is a coenzyme found in all living cells. It is involved in energy production and serves as a required partner for enzyme families including sirtuins, which help regulate gene activity in response to the cell's metabolic state.
The 2009 findings that linked the two
In 2009, two research groups published companion papers in the journal Science that connected NAD+ directly to the circadian clock. One team, led by Kathryn Moynihan Ramsey and Joseph Bass, reported a feedback cycle in which the clock machinery regulates NAMPT, a key enzyme in the "salvage" pathway that recycles NAD+. A second team, led by Yasukazu Nakahata and Paolo Sassone-Corsi, described how the CLOCK protein and the NAD+-dependent enzyme SIRT1 jointly control that same salvage pathway.
Taken together, the papers suggested that NAD+ levels in cells rise and fall over the course of the day, and that NAD+ itself feeds back into the clock through sirtuin activity. In other words, metabolism and timekeeping appeared to be wired together rather than running as separate systems.
Aging and the clock
Later work extended those ideas into aging. A 2020 study in the journal Molecular Cell, led by Daniel Levine and colleagues in Joseph Bass's laboratory, examined how declining NAD+ in older mice related to changes in circadian gene activity, and explored what happened when NAD+ levels were raised experimentally in those animals. The study added to a broader body of research documenting that NAD+ tends to fall with age in several tissues and that circadian rhythms tend to weaken with age as well.
These are important findings for basic science. They are also animal and cell studies. Researchers have been careful to note that rodent clocks, rodent metabolism and rodent lifespans differ from those of people, and that a mechanism observed in a laboratory model does not establish what will happen in a human patient.
What researchers are still trying to answer
The current scientific conversation around NAD+ and circadian biology is defined as much by its open questions as by its findings. Among the issues researchers continue to investigate:
+ Translation to humans: whether the clock-NAD+ relationships seen in mice operate the same way in human tissues, and to what degree.
+ Delivery and timing: how different routes of administration affect NAD+ levels in specific tissues, and whether the time of day matters given the molecule's daily oscillation.
+ Measurement: how best to measure NAD+ status in people, since blood levels may not reflect what is happening inside individual organs.
+ Who might be relevant: which populations, if any, are appropriate candidates for supplementation or prescribed protocols, and which are not.
+ Long-term data: what longer and larger human studies will show, as most published human research to date has been relatively small and short.
For now, the honest summary is that research is exploring a plausible and scientifically interesting connection. It has not been established that any NAD+ product improves sleep or resets the body clock in people, and clinicians who work with NAD+ generally avoid framing it that way.
The fundamentals still come first
Sleep researchers consistently point to behavioral factors that are known to shape circadian timing: consistent sleep and wake times, morning light exposure, limiting bright screens late at night, and the timing of meals and exercise. None of the emerging NAD+ research displaces those basics. If anything, the clock-metabolism link highlights why routine and timing matter across the board.
How it works in practice
Interest in the science has grown, so has the number of people asking clinicians about NAD+. Telehealth has become a common route to that conversation. HealSend, a LegitScript-verified U.S. telehealth pharmacy, offers NAD+ injection therapy through a clinician-led online process rather than as an over-the-counter product.
Patients complete a short online form, which the company describes as taking about 90 seconds, and connect with a licensed medical provider who reviews their health history and goals online, with no office visit required. Treatment is offered only if the clinician finds it appropriate. When a patient is eligible, a prescription compounded in the U.S. is shipped to their door in discreet packaging as an at-home subcutaneous kit with instructions, and the frequency of use is set by the clinician rather than by the patient.
HealSend lists ongoing follow-up messaging and refill coordination as part of the service, with a care team available seven days a week. The company states that HSA and FSA funds are accepted, displays Klarna and Afterpay as payment options, and describes plans as month-to-month. Availability is limited to the U.S. states where it operates, and eligibility always depends on a licensed clinician's assessment.
Trends to watch
Chronobiology goes mainstream
Concepts that were once confined to research labs, such as chronotypes, circadian misalignment and time-restricted eating, are now part of everyday wellness vocabulary. Consumer wearables have accelerated that shift by giving people nightly data on sleep duration and timing. Expect more products, and more marketing, to borrow the language of circadian science, and expect regulators and researchers to push back on claims that outrun the evidence.
Telehealth as the access point
Telemedicine has become a routine part of clinical practice. According to the CDC's National Center for Health Statistics, the share of office-based physicians using telemedicine rose from 15.4 percent in 2019 to 86.5 percent in 2021. That infrastructure now supports a wide range of wellness consultations, including conversations about sleep, energy and healthy aging that patients may never have raised in a short in-person visit.
Better human data
The most important development in the field will be the arrival of larger, longer human trials. Those studies will help determine whether the elegant mechanisms seen in the laboratory have practical relevance for people, and for whom. Until then, careful clinicians are likely to continue treating NAD+ as an individualized wellness option rather than a sleep intervention.
Conclusion
The flat line in the CDC's sleep data is a reminder that knowing about sleep and getting enough of it are two different things. Circadian science has given researchers a much richer picture of why timing matters, and the discovery that NAD+ and the body clock appear to regulate one another is one of the more intriguing chapters in that story.
That chapter is still being written. The strongest findings so far come from cell and animal research, and the questions that matter most to people, about translation, timing and long-term effects, remain open. For anyone following the field, the most useful stance is curiosity paired with patience: watch the human data as it arrives, keep the well-established sleep fundamentals in place, and treat any conversation about NAD+ as one to have with a qualified clinician.
