Probably not. They seem to improve healthspan -- the health you experience during your years -- but not lifespan, the total number of years.
It just seems intuitive that if you replenish NAD levels that would otherwise decline, then you'll be healthier, and better health will inevitably lead to longer life. But the science does not consistently show that.
NAD and Aging
Scientists have been pretty exited about the anti-aging potential of NAD precursors.
The theory is very straightforward: Aging may result from cumulative DNA damage. DNA repair processes require NAD. Sustaining NAD levels may enable more repair and less cumulative damage. It seems to work in some animals.
Cumulative evidence indicates that impaired genomic maintenance may causally contribute to aging. An age-dependent accumulation of DNA damage occurs in humans, possibly due to impaired DNA repair. This suggests that maintenance of efficient DNA repair may delay the onset of aging and age-related diseases. NAD+ replenishment can improve DNA repair in cells, C. elegans, and mice.
Indeed, NAD decline correlates with aging, and there is a lot of evidence that NAD decline actually contributes to the aging process.
There is a growing body of evidence which suggests that NAD+ decline is a major contributor to the aging process and may be involved in the pathogenesis of several age-related degenerative diseases affecting the heart, brain, liver, kidney, and skin. These results collectively highlight the potential for NAD+ supplementation, whether using NAD+ alone or NAD+ precursors to protect against aging and associated pathologies...Given that NAD+ levels are elevated under conditions of increased life span or health span, decline under conditions of accelerated aging and/or reduced health span suggests that reduced NAD+ levels may represent a major contributor to the aging process. Therefore, supplementation with NAD+ and its precursors may represent a potential therapeutic strategy to mediate protection against accumulation of inflammation and highly volatile reactive oxygen species (ROS) during the aging process
So there is good reason to believe that taking care of yourself in all kinds of ways, including sustaining NAD levels, could help you age better.
But to be clear, being healthier as you grow older is different from aging backwards or living longer. There is good evidence that NAD replenishment can sustain health, but about living longer, we don't really know. Most of the research has focused on curing diseases in sick people, not increasing lifespan in healthy individuals:
In mice, most studies have been performed using different disease models and relatively little is known how NAD+ precursor supplementation affects the longevity and healthspan of wild type mice.
A relatively early study found that when two-year old mice took NR, their lifespan improved by about a month, which for a mouse is not bad. Moreover, said the scientists,
Although the life span benefit is small, it was obtained with the NR treatment commencing late in life at 24 months
However, a subsequent study failed to find any difference in the lifespan of mice that took NR:
NR has no effect on lifespan in the genetically variable mice that best model the human population
Another recent study of Nicotinamide Riboside found that NR improved rats' health and made them more youthful in all kinds of different ways, but also found that the NR did not actually increase their lifespan:
In this study, [we showed that Nicotinamide Riboside and Metformin] improved various aspects of healthspan in rats but did not statistically alter their lifespan
And often when you read about NAD precursors helping mice live longer, it turns out that the effect was observed in mice that were desperately ill with some horrible disease like Leigh Syndrome, where indeed lifespans are improved with NAD precursors. But that doesn't tell us anything about whether NAD replenishment can increase lifespan in otherwise healthy mice, let alone otherwise healthy humans.
In this study, scientists found that although small doses of nicotinamide (NAM) increased lifespan in worms, larger doses of NAM actually reduced lifespans. This was likely due to the toxic effects of NAM at high levels.
Administration of low concentrations of Nam, μM range, to C. elegans increased lifespan. In contrast, higher doses of Nam, mM range, reduced lifespan. Thereby, the effect of Nam on lifespan extension is unclear. This discrepancy might be due to the inhibitory effect of Nam at high concentrations on sirtuins and PARPs. Another possible explanation is that high concentrations of Nam can deplete cells of S-adenosyl methionine (SAM), a vital substrate for methylation reactions, as Nam is methylated to N-methyl Nam (MNAM) and secreted. This process, in turn, might affect DNA methylation and lead to aberrant gene expression....the positive impact of NR supplementation on the lifespan of both C. elegans and yeast is well established.
By contrast, nicotinamide riboside (NR) lengthened lifespans in both yeast and worms at all doses:
The positive impact of NR supplementation on the lifespan of both C. elegans and yeast is well established.
But that's just yeast and worms. That doesn't mean it has that effect in mice or humans.
On the other hand, there was just very recently a study that tested all kinds of health supplements -- rapamycin, metformin, resveratrol, aspirin, antioxidants, and more, including niacin and nicotinamide riboside -- in a mouse model of aging based on the ability to repair DNA damage. NR significantly extended lifespan, by 25%, beyond the maximum age reached by any of the other drugs tested. In fact none of the other supplements extended lifespan by a significant amount, not even niacin; only nicotinamide riboside:
Interestingly, mice supplemented with NA revealed a significant delay in the onset of imbalance, whereas NR supplementation showed a trend towards delaying the median age of onset of tremors. Furthermore, NR significantly extended median lifespan by approximately 25% or 5 weeks, while animals receiving NA lived about as long as control-fed animals.
Well, that's one mouse study.
Although, another study noted,
Numerous studies have shown that NR can increase the lifespan of all species tested so far, including mice...
So it's not a crazy idea. But it has not been shown in humans, and likely will not be for a long time.
Conclusion
It's probably wiser to think of NAD boosting as a way to increase healthspan, rather than lifespan. There are studies that show life extension as a result of nicotinamide riboside supplementation in yeast, worms, and now mice. But certainly no such studies in humans. NAD boosters really do seem to help people live better. But whether they live longer remains to be seen.
Read More: Studies involving NAD and Aging
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