Study to Evaluate the Effect of Nicotinamide Riboside on Immunity: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study to Evaluate the Effect of Nicotinamide Riboside on Immunity (NCT02812238), a randomized na study. The primary outcome is Mean IL-1 Beta Release From Peripheral Blood Mononuclear Cells During Refeeding After 24 Hour Fast.

2. Clinical Question

3. Trial Design

The study was randomized, quadruple masked, and used a crossover model. In a crossover trial, participants receive more than one study treatment in different periods, so treatment comparisons can be made within the same participant when the analysis uses the paired data appropriately. The registry description says participants received NR once and placebo once, without knowing which they were taking. Both arm descriptions specify one week of treatment followed by a washout period and then a crossover to the other treatment. The record lists a washout period of 2-3 weeks in those arm descriptions.

The brief summary describes participants taking four pills of NR or placebo daily for one week, not eating or drinking on day 6, and providing blood samples before and after a meal on day 7. It says the day 6 and day 7 procedures were repeated during the other treatment period. The primary outcome timeframe is listed as 4 weeks. These descriptions place the outcome in the setting of fasting and refeeding, rather than describing a routine measurement outside that context.

The registry lists an enrollment of 38. The primary outcome summaries list 36 observations for NR and 36 for placebo. The record does not explain the difference between the enrollment figure and the numbers reported for each treatment, nor does it state whether those outcome counts represent complete paired records or another analysis population. The allocation sequence, crossover sequence counts, and participant flow are not reported in the registry record.

The study is marked completed. The phase is listed as NA. Details of the original sample-size justification, the planned statistical analysis, and any interim analyses are not reported in the registry record. The record also does not describe whether the analysis accounted for treatment period, treatment sequence, or possible carryover between periods. Those details matter for interpreting a crossover comparison, but should not be inferred from the design label alone.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

First Intervention

Second Intervention

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Mean IL-1 Beta Release From Peripheral Blood Mononuclear Cells During Refeeding After 24 Hour Fast, measured over 4 weeks.

The primary outcome is the mean IL-1 beta release from peripheral blood mononuclear cells during refeeding after a 24 hour fast. The listed unit is mg/dL. Peripheral blood mononuclear cells are the blood-cell sample named in the outcome; the registry describes measuring their IL-1 beta secretion in response to fasting, refeeding, and NR or placebo.

The registry’s rationale is that NR is intended to act as a fasting mimetic and is supposed to maintain a reduction in IL-1 beta secretion associated with fasting. It describes IL-1 beta secretion as indicating NLRP3 inflammasome activation. In this context, the endpoint is a laboratory measure intended to capture an immune-related response around refeeding, rather than a clinical event or a direct measure of how participants feel or function.

The outcome is continuous and summarized as a mean with standard deviation. A mean describes the group’s average measured release, while the standard deviation describes the spread of individual measurements around that average. The posted means are 582.0 mg/dL for NR and 794.0 mg/dL for placebo. The registry does not report the assay procedures, measurement validation, or a clinically meaningful threshold for interpreting a difference in this laboratory measure. The endpoint therefore supports interpretation of the measured biomarker comparison, not conclusions about clinical benefit.

7. Results Posted in the Registry

• Nicotinamide Riboside: mean 582.00 versus 794.00 on control; difference -212.00 (95% CI -578.68 to 154.68), standardized effect d = -0.27; z-test p = 0.257.

8. Statistical Interpretation

9. Statistical Methods Explained

The outcome is continuous, so the registry summarizes it with means and standard deviations. The mean is the arithmetic average of the measured values. The standard deviation describes how dispersed measurements are around that average; a larger standard deviation indicates more variation among observations, not necessarily a larger treatment effect. For NR, the posted mean is 582.0 mg/dL and the standard deviation is 612.0 mg/dL. For placebo, the mean is 794.0 mg/dL and the standard deviation is 941.0 mg/dL. These summaries describe each treatment’s observations separately.

A mean difference expresses the contrast between the treatment means on the outcome’s original scale. The posted contrast for NR compared with placebo is -212.0 mg/dL. The sign gives direction according to the comparison as reported: the estimated mean is lower for NR. The size remains uncertain, so the point estimate should not be read as a precise or definitive treatment effect. The record does not report a clinically meaningful difference for this laboratory outcome, which limits interpretation of the estimate’s practical importance.

The interval from -578.7 to 154.7 mg/dL gives a range of values compatible with the estimate under the interval’s statistical assumptions. General statistical interpretation: an interval is more informative than a point estimate alone because it shows uncertainty in the estimated contrast. When an interval includes zero for a difference, it includes no difference as one value compatible with the data and model. The registry record does not specify the confidence level or the procedure used to construct this interval, so those details should not be assumed.

The reported p-value is 0.257. In general, a p-value measures how unusual the observed result, or a more extreme result, would be if a stated null hypothesis and the test’s assumptions held. It does not quantify the size or importance of a difference. It is also not a measure of the chance that a finding is false. The record does not identify the null model, test statistic, or analysis procedure behind this p-value, so the value can be reported but its exact analytic basis cannot be assessed from the registry record.

Randomization is intended to make treatment assignment independent of participants’ characteristics, on average, and masking can limit some influences of knowing which treatment is being taken. The record labels this study randomized and quadruple masked. It does not define the four roles covered by masking or report the success of masking. In a crossover design, each participant receives both treatments, which can help control stable differences between participants when the analysis compares their outcomes appropriately. That advantage depends on the analysis preserving the paired structure and on assumptions about the periods and treatment sequence.

General statistical considerations for crossover trials include accounting for treatment period and sequence and considering whether a prior treatment could influence outcomes in a later period. These are design and analysis issues, not evidence that a problem occurred in this study. The registry record does not report the model used, whether period or sequence terms were included, how carryover was assessed, or whether the posted comparison used paired participant-level data. The treatment-specific means and standard deviations do not answer those questions. The record also does not provide participant-level measurements or the standard deviation of within-participant differences, so an independent reconstruction of a paired treatment analysis is not possible from the summaries alone.

The study’s planning assumptions are described separately from its reported trial results. They use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The planning illustration uses a specified fraction of the observed effect as the effect to detect. It is not evidence about the original trial’s design calculations; the original sample-size justification and the trial’s own analysis plan are not reported in the registry record. The listed power-based participant counts are planning illustrations, not a description of the trial’s achieved power.

The record lists one primary outcome and no posted secondary outcomes. It reports no analysis entries. The analysis populations, handling of missing measurements, and any adjustment for multiple testing are not reported in the registry record. General statistical interpretation: a complete account of these choices helps readers judge whether the reported estimate follows the planned analysis and how robust it is to missingness or multiple comparisons. Without those details, the posted estimate and its interval remain useful descriptive evidence, but the analytic process cannot be fully audited from the registry record.

10. Confidence Intervals and Precision

The mean difference is -212.0 mg/dL, and the reported interval runs from -578.7 to 154.7 mg/dL. The interval covers zero and extends to values favoring either treatment direction. This breadth indicates that the estimate does not pin down a narrow range for the treatment contrast. It allows for a meaningful lower mean during NR, little or no difference, and a higher mean during NR, without establishing which possibility best describes the underlying effect.

General statistical explanation: an interval reflects both the observed estimate and uncertainty arising from sampling and the statistical model. It should not be interpreted as a list of outcomes that actually occurred, or as a probability statement about a particular fixed effect without reference to its construction. The registry record does not identify the interval’s confidence level or construction method. As a result, its endpoints can be quoted, but its exact long-run coverage interpretation cannot be checked from the record.

The group standard deviations are 612.0 mg/dL for NR and 941.0 mg/dL for placebo. The observed outcome summaries therefore include substantial variability. In a crossover study, however, the standard deviations within each treatment period are not enough to determine the precision of the paired treatment contrast. Precision also depends on how strongly measurements from the same participant are related across periods. The registry does not report paired differences or their standard deviation, so the contribution of that within-person relationship cannot be evaluated.

The posted outcome counts are 36 for each treatment, compared with an enrollment of 38. The record does not describe which participants contributed to the endpoint summaries or why the counts differ. Missing or incomplete paired observations can affect precision and may also affect the estimated contrast, depending on why measurements are absent. The record does not report missing-data methods or a sensitivity analysis. The interval is therefore best read as the uncertainty attached to the posted comparison, not as a complete account of uncertainty from every possible source.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size figures are participants per arm, not total events. The planning illustration assumes a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Its target effect is set to a stated fraction of the observed effect. These are planning assumptions for the illustration; the trial’s own original design assumptions and sample-size justification are not reported in the registry record.

For planning at 100% of the observed effect, the figures are 221 participants per arm for 80% power and 295 participants per arm for 90% power. At 75% of the observed effect, the figures are 392 participants per arm for 80% power and 524 participants per arm for 90% power. At 50% of the observed effect, the figures are 881 participants per arm for 80% power and 1,179 participants per arm for 90% power.

In general, power is the probability that a study will detect an effect of the specified size under the planning assumptions, if that effect is present and the model assumptions hold. The 80% column gives the planned number per arm associated with an 80% chance of detecting that target effect; the 90% column gives the number associated with a 90% chance. Smaller target effects require more participants to distinguish them from random variation with the same planned power. The curve represents the same planning relationship across effect sizes; it should be read as a design illustration, not as a result from the trial. These figures are not observed power.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -212.000; pooled standard deviation σ = 793.733.
2. n = 2 × (1.96 + 0.842)² × 793.733² / -212.000² = 220.0, rounded up to 221 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -212                      # observed difference in means
sigma <- 793.733267540173                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(2812238)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 221 (80% power), 295 (90% power)
 75% of observed effect: n per arm = 392 (80% power), 524 (90% power)
 50% of observed effect: n per arm = 881 (80% power), 1,179 (90% power)
power.t.test: 221 
Simulated power at n = 221 per arm: 0.799 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome and no posted secondary outcome results. It reports no analysis entries. The record does not state whether other outcomes or analyses were prespecified, whether additional comparisons were conducted, or whether any adjustment for multiple testing was planned. Consequently, the effect of multiplicity on the reported p-value cannot be assessed. General statistical explanation: when many outcomes or analyses are examined, the chance of at least one apparently unusual result can increase, and a prespecified analysis plan helps readers interpret that risk. No such plan is reported in the registry record.

The outcome summaries list 36 observations for NR and 36 for placebo, while the study enrollment is 38. The record does not say why the outcome counts are lower than enrollment, whether all participants completed both treatment periods, or whether observations were excluded. It does not report imputation, a complete-case rule, a missing-data sensitivity analysis, or reasons for missing measurements. The consequences of missing data therefore cannot be judged from the posted record.

The registry does not identify the analysis population, such as whether all randomized participants or only participants with measurements in both periods were included. It also does not state how the crossover data were modeled, whether the analysis was paired, or whether period and sequence were accounted for. These omissions matter because the design involves repeated treatment periods within participants. The results can be interpreted as the posted treatment summaries and comparison, but the analysis population and the handling of incomplete or correlated measurements are not reported in the registry record.

The record does not report interim analyses, stopping rules, or multiplicity procedures. Those details should not be inferred from the completed status or from the single posted primary outcome. The absence of reported information does not establish that a procedure was or was not used; it means the registry record does not permit readers to evaluate it.

14. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports serious adverse events for 0 of 38 participants in the NR group and 0 of 38 in the placebo group. It also reports 0 deaths in each group. These are counts for the listed groups; they do not establish that no adverse experiences of any kind occurred.

The record separately lists other, non-serious adverse events affecting 3 of 38 participants in the NR group and 2 of 38 in the placebo group. Those counts are distinct from the serious-event figures and should not be combined with them. The registry does not provide event descriptions in the serious-event terms list, which is empty, or further detail about timing, severity categories for other events, or whether any event was considered related to treatment.

Safety counts describe what was recorded in these study groups. With the study’s reported enrollment and outcome summaries, they should not be treated as a precise estimate of the frequency of uncommon events or as a comparison that establishes a safety difference. The registry record does not report additional safety analyses or follow-up detail.

15. What the Result Does, and Does Not, Mean

The posted data show that the mean IL-1 beta release was lower in the NR summary than in the placebo summary, with a reported mean difference of -212.0 mg/dL. The interval from -578.7 to 154.7 mg/dL includes zero and extends in both directions. The unadjusted p-value is 0.257. Together, these results do not provide a precise, clear estimate of a difference between treatment periods. They do not prove that there is no difference, and they do not establish that the treatments are equivalent.

The endpoint is a laboratory measure collected in the context of fasting and refeeding. The registry’s stated rationale links IL-1 beta secretion with NLRP3 inflammasome activation and describes NR as a fasting mimetic. The posted comparison concerns the measured biomarker, not a clinical outcome. The record does not report a clinically meaningful threshold for this measure or establish how a change in it would relate to health outcomes.

The result also cannot, on its own, answer whether the effect lasts after eating again or whether NR has the same immune effects as fasting. Those are questions in the study’s stated objectives, but the registry record posts only the primary outcome comparison and no secondary outcome results. The measured outcome and reported summaries do not show how participants responded on other immune measures or over longer follow-up.

Interpretation is limited by the absence of detail on the crossover analysis, paired measurements, analysis population, and missing data. Those features could affect both the estimated difference and its precision. The most supportable reading is therefore narrow: in the posted summaries, the estimated mean was lower during NR than during placebo, but the interval is broad and the analysis details needed for fuller evaluation are not reported in the registry record. These data should not be extended to people or settings beyond the study description, or treated as evidence of clinical benefit or harm.

16. Why This Trial Matters Statistically

This trial illustrates why a treatment contrast needs to be read alongside its uncertainty. The point estimate is negative, but the interval includes values on either side of zero. Focusing only on the direction of the estimate would leave out the substantial uncertainty about how large the difference might be and which direction the underlying contrast could take.

The crossover design also highlights a distinction between treatment-specific summaries and a treatment comparison. Each participant was intended to receive both NR and placebo, so within-participant information can be central to the precision of the contrast. The reported means and standard deviations describe the treatment summaries, but do not show the relationship between each participant’s measurements across periods. The registry does not report whether or how that paired structure was incorporated into the analysis.

The sample-size illustration demonstrates how the target effect and desired power affect planning. Its participant counts rise as the target fraction of the observed effect becomes smaller. That relationship is a planning concept, not an explanation of why the completed study enrolled its participants; the original sample-size justification is not reported in the registry record. Separating design planning from achieved results helps prevent interpreting power calculations as evidence that the trial did or did not find an effect.

Finally, the record distinguishes a laboratory endpoint from a clinical outcome. The stated biological rationale gives context for why IL-1 beta release was measured, but the posted result alone does not establish the clinical meaning of a change in that biomarker. Clear reporting of the analysis model, paired data, missing measurements, and endpoint interpretation would help readers judge the result more fully.

17. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

Several trial-specific details needed to interpret the result are not reported in the registry record. Although the design is labeled crossover, the analysis model and treatment contrast method are not described. There are no paired participant-level summaries, so it is not possible to assess the within-person variation that may influence precision. The record also does not say whether period, treatment sequence, or possible carryover were addressed.

The enrollment is 38, while the primary outcome summaries contain 36 observations for each treatment. The record does not explain participant flow, whether all participants completed both periods, or how incomplete measurements were handled. The analysis population and missing-data methods are not reported. The posted summaries therefore do not show whether missing observations could have affected the treatment estimate.

The brief summary identifies healthy volunteers ages 18–39 years, while the condition list includes atherosclerosis, diabetes, and coronary artery disease. The record does not explain this difference or clarify how the condition list relates to participant eligibility. The results should be interpreted with that population description in mind, without assuming a broader or different enrolled population.

The registry describes IL-1 beta secretion as an indicator of NLRP3 inflammasome activation, but does not report assay details, measurement validation, or a clinically meaningful threshold. It posts no secondary outcome results and does not provide the original analysis plan or sample-size justification. The interval construction and confidence level are also not identified. These reporting gaps limit evaluation of the biological measurement, statistical approach, and clinical relevance of the observed contrast.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Study to Evaluate the Effect of Nicotinamide Riboside on Immunity — NCT02812238.
• Registry record last updated 2019-09-17; status last verified 2019-04-03.
• Results first posted 2019-09-17.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

21. Record Summary

The registry describes a completed randomized, quadruple-masked crossover study of nicotinamide riboside and placebo. Enrollment was 38. The primary outcome was mean IL-1 beta release from peripheral blood mononuclear cells during refeeding after a 24 hour fast, with a listed timeframe of 4 weeks.

The posted means were 582.0 mg/dL for NR and 794.0 mg/dL for placebo, with standard deviations of 612.0 mg/dL and 941.0 mg/dL, respectively. The reported mean difference was -212.0 mg/dL, with an interval from -578.7 to 154.7 mg/dL and an unadjusted p-value of 0.257. The outcome summaries list 36 observations for each treatment.

The registry lists no secondary outcome results and does not report the analysis model, analysis population, or missing-data approach. It reports 0 serious adverse events and 0 deaths in each group. The posted biomarker comparison is uncertain and does not establish a clinical effect.