Impact of Oxytocin on Obstructive Sleep Apnea Induced Changes in Sleep: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Impact of Oxytocin on Obstructive Sleep Apnea Induced Changes in Sleep (NCT03148899), a randomized phase 2 study. The primary outcome is Duration of Obstructive Events.

2. Clinical Question

The registry frames the work as an exploration of whether intranasal oxytocin has cardiovascular benefits during sleep apnea. Its primary endpoint, however, is the duration of obstructive events, rather than a cardiovascular event or a direct measure of cardiovascular benefit. Respiratory rate, incidence proportion of bradycardia, and minimum oxygen saturation are listed as secondary outcomes. These measures add information about breathing and oxygenation, but they do not by themselves establish a change in cardiovascular risk.

The comparison is within a randomized crossover study: participants were assigned to one intervention at the first visit and received the other intervention at the second. The registry’s visit descriptions therefore define the question as a contrast between the two treatment conditions across visits. The record does not report additional details about how visit order, time, or possible carryover effects were handled in the analysis.

The clinical question is consequently narrow: whether the recorded sleep-related measures differed between oxytocin and placebo conditions in this study. It is not a test of longer-term clinical outcomes, and the posted results do not establish whether any observed difference would translate into a broader cardiovascular effect.

3. Trial Design

This is a Phase 2 randomized, triple-masked, crossover trial of intranasal oxytocin and placebo. The registry lists 32 enrolled participants and identifies obstructive sleep apnea as the condition under study. The trial is marked completed, with a start date of 2016-07-27 and a primary completion date of 2020-06-07. George Washington University is listed as the sponsor.

The crossover structure is central to interpreting the design. At Visit 1, described as PSG 1, participants received either oxytocin intranasal spray or placebo intranasal spray. At Visit 2, described as PSG 2, each participant received the opposite intervention. The registry’s arm descriptions state that participants were blinded to which drug they were receiving. The record labels masking as triple, but does not specify which three groups of people were masked.

The outcome time frame is Visit 1 on Day 1 and Visit 2 on Day 29. The primary outcome is a continuous measure reported as a mean and standard deviation. Three secondary outcomes are also posted: respiratory rate, incidence proportion of bradycardia, and minimum oxygen saturation. The registry reports 19 participants in each treatment condition for the posted outcome summaries. It does not explain how those outcome denominators relate to the total enrollment or provide a participant-flow account.

Although crossover trials can use each participant’s experience under both conditions, the record does not report whether the posted comparisons used paired participant-level data, nor does it describe an adjustment for period or sequence. It also does not report a washout procedure, the trial’s original sample-size justification, or a detailed statistical analysis plan. Those omissions limit what can be concluded about the analysis choices from the registry record 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.

Before assignment: 36 subjects with OSA were assessed for eligibility and willingness to participate in this double blinded cross over placebo-controlled trial. Four subjects declined to participate. The remaining 32 subjects were randomly assigned to receive either placebo (n=16) or oxytocin (n=16) in the first visit, then a washout period within 4 weeks, then the other intervention they did not receive in the second visit.

Overall Study

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.

Population: There were 32 participants total, 16 in each arm.

6. Primary Endpoint

The registry lists the primary outcome as Duration of Obstructive Events, measured over Assessed on Visit 1- Day 1, Visit 2- Day 29.

The primary endpoint is the duration of obstructive events, measured in seconds. It describes how long an obstructive event lasts during the sleep assessment. The registry lists assessment at Visit 1 on Day 1 and Visit 2 on Day 29, corresponding to the two visits in the crossover design.

This measure is relevant to the study’s stated question because obstructive events are a defining feature of sleep apnea, and their duration captures an aspect of the breathing disturbance during sleep. A comparison between the oxytocin and placebo conditions can therefore describe whether the average recorded duration differed between those conditions in the posted results.

Duration is not the same as the number of events, their severity, oxygen desaturation, or a cardiovascular event. The registry does not describe a threshold for what constitutes a clinically important change in event duration, and it does not report a minimum important difference. The outcome is reported as a mean and standard deviation, so the summary emphasizes the average and the spread of measurements rather than individual participant trajectories.

The endpoint can address a specific physiological feature measured during the study visits. By itself, it cannot establish whether a difference changes symptoms, long-term cardiovascular outcomes, or health outside the assessment setting. The posted mean comparison should therefore be read as a result about recorded event duration, not as a complete measure of OSA burden or cardiovascular benefit.

7. Results Posted in the Registry

• Oxytocin: mean 22.72 versus 24.66 on control; difference -1.94 (95% CI -5.03 to 1.15), standardized effect d = -0.40; z-test p = 0.219.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Respiratory Rate

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Oxytocin: mean 17.39 versus 16.69 on control; difference 0.70 (95% CI -1.44 to 2.84), standardized effect d = 0.21; z-test p = 0.522.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Oxytocin and the control. The interval gives the range of effects that remain compatible with the data.

Incidence Proportion of Bradycardia

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Oxytocin: mean 0.08 versus 0.14 on control; difference -0.06 (95% CI -0.10 to -0.02), standardized effect d = -0.86; z-test p = 0.008.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Oxytocin than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

O2 Minimum

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Oxytocin: mean 94.31 versus 92.44 on control; difference 1.87 (95% CI -0.20 to 3.94), standardized effect d = 0.57; z-test p = 0.077.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Oxytocin and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes cover different aspects of breathing and oxygenation: respiratory rate, incidence proportion of bradycardia, and minimum oxygen saturation. Taken together, their posted estimates do not present a single consistent pattern across all measures. The contrasts vary in direction and in how precisely they are estimated, so the endpoints should be read individually as exploratory information rather than combined into a general conclusion about the primary result.

These measures complement the primary endpoint because they describe other features recorded during the sleep assessments. They do not replace the primary measure of obstructive-event duration, and they do not directly answer whether duration changed. Nor does a pattern across these secondary measures establish a cardiovascular effect beyond the outcomes actually recorded.

The registry lists no reported analyses for the secondary outcomes. The comparisons are unadjusted, and the record does not state how many outcomes or contrasts were considered in the statistical plan. When several outcomes are examined, the chance of obtaining an apparently notable result by chance can increase. Without a reported multiplicity strategy, isolated secondary findings carry less evidential weight than a prespecified, appropriately analyzed primary comparison.

That caution is particularly relevant when secondary endpoints differ in scale and variability. A mean difference for respiratory rate, a proportion measure for bradycardia, and an oxygen saturation measure are not interchangeable quantities. They should not be averaged into a single informal judgment or treated as if each independently confirmed the primary result. The record offers descriptive estimates, but not a reported framework for combining or prioritizing them.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Respiratory Rate
• Incidence Proportion of Bradycardia
• O2 Minimum

9. Statistical Interpretation

10. Statistical Methods Explained

The registry reports continuous outcomes as means and standard deviations. A mean describes the average observed value in a condition; a standard deviation describes how dispersed the individual values are around that average. For the primary endpoint, the mean difference is expressed as oxytocin minus placebo. Its negative estimate means the oxytocin condition had a lower posted mean duration than the placebo condition. The estimate remains a summary contrast and does not show how each participant’s value changed between visits.

What does a confidence interval describe?

General explanation: a confidence interval gives a range of values compatible with the data and the method used to calculate it. It communicates uncertainty around an estimate; it is not a range containing a stated proportion of individual participants. For the primary contrast, the interval extends from -5.032 to 1.152 seconds. Because it includes zero, the posted summary does not rule out no mean difference under the calculation used. Its width also indicates that meaningfully different values remain compatible with the result. The registry does not state the confidence level or give a trial-specific method for the interval.

How should the p-value be read?

General explanation: a p-value measures how unusual data at least as discrepant as the observed data would be under a specified null model. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of a difference. The primary unadjusted p-value is 0.219. It should be read alongside the estimate and its interval, not in isolation. The registry does not report a complete inferential analysis plan, and the listed analysis count is 0.

Why does the crossover design matter?

General explanation: in a crossover study, the same participant receives more than one condition, so a comparison can use within-person information. The correlation between a participant’s measurements under the conditions can affect the uncertainty of a paired estimate. The registry describes a randomized crossover and opposite interventions at the two visits, but it does not report whether the posted comparison used paired data, how visit order was handled, or whether period or carryover effects were considered.

The comparison figures are simple unadjusted recalculations from the posted summary statistics. They are not described as a sponsor-reported analysis. The registry does not provide the covariance needed to reconstruct a paired comparison from the posted means and standard deviations alone. Consequently, these recalculations describe the contrast in the available summaries but cannot reproduce every possible crossover analysis. Since the discrepancy flag is false, there is no identified disagreement with a sponsor analysis; that does not supply the missing analysis details.

What do standard deviations and standard errors add?

General explanation: a standard deviation describes spread among observations, whereas a standard error describes uncertainty in an estimated quantity under a statistical model. Neither is interchangeable with the other. The posted arm summaries give standard deviations for the outcomes. The recalculation fields also include standard errors, but the registry does not explain a participant-level model that would clarify their interpretation in this crossover setting. The summaries should therefore be kept distinct from a full analysis of repeated measurements.

The outcome is a continuous measure, and the posted contrast uses a mean difference. This is a direct scale-based description: the primary estimate is expressed in seconds. The calculation also reports a standardized effect-size summary, but that summary does not replace the original-unit result. For clinical interpretation, seconds remain the natural scale for the endpoint, while the interval communicates uncertainty about the mean contrast.

The secondary outcomes are also posted as continuous means and standard deviations, including the incidence proportion of bradycardia. The record does not report a separate analysis method for that measure, such as a model for event counts or proportions. Nor does it report adjusted analyses for the secondary endpoints. Their unadjusted estimates can be described, but they do not establish that all planned comparisons were handled in a prespecified way.

Overall, these methods explain the descriptive contrasts that can be read from the registry results. They do not fill gaps in the original statistical plan, the participant-level data, the crossover analysis, or the handling of missing measurements. Those details are not reported in the registry record.

11. Confidence Intervals and Precision

The primary mean difference is -1.94 seconds, with a confidence interval from -5.032 to 1.152 seconds. The interval crosses zero, so the posted estimate is compatible with both a lower mean duration under oxytocin and a higher mean duration under oxytocin, relative to placebo, under the calculation used. It does not identify a single precise value for the difference.

The point estimate is not the full result. Its uncertainty matters because the interval includes values on either side of zero and spans a range of possible mean contrasts. The interval does not establish that the conditions are equivalent: no equivalence margin is reported, and an interval containing zero is not by itself an equivalence test. The registry also does not report a minimum clinically important difference for event duration, so the clinical importance of values within the interval cannot be determined from the record.

There are 19 participants in each posted treatment-condition summary, while the registry lists 32 enrolled overall. The record does not explain the relationship between these figures, nor does it provide participant-level missingness or a reason for the outcome denominators. It is therefore not possible to assess from these summaries whether incomplete data, exclusions, or other factors affected precision.

The crossover design could make within-person comparisons informative, but the summary does not report the paired correlation or the method used to account for repeated measures. That missing information limits an assessment of the precision appropriate to the design. The interval should be interpreted as attached to the posted unadjusted summary comparison, rather than assumed to represent a fully documented crossover analysis.

12. 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 planning illustrations based on the observed effect, not the trial’s original sample-size calculation. They show participants per arm for the continuous outcomes in this study. The event-total convention for time-to-event outcomes does not apply, because the posted outcomes are continuous measures.

The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set in turn to 100%, 75%, or 50% of the observed effect. The registry does not report the assumptions or justification used to choose the original trial enrollment.

The 80% power column means the illustrated number of participants per arm for a design with an 80% chance of detecting the specified effect under those assumptions, if that effect and model were correct. The 90% power column uses a higher target chance of detection, so its planning figures are larger. These columns are planning targets, not descriptions of what happened in the completed study.

Smaller effects are harder to distinguish from random variation, so the illustrations require more participants per arm when the targeted effect is a smaller fraction of the observed effect. The estimates depend on the observed effect used as their starting point and should not be interpreted as a recommendation or as proof that the study was adequately powered. This is not observed power.

13. 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 = -1.940; pooled standard deviation σ = 4.862.
2. n = 2 × (1.96 + 0.842)² × 4.862² / -1.940² = 98.6, rounded up to 99 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 <- -1.94                      # observed difference in means
sigma <- 4.86222685608148                     # 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(3148899)
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 = 99 (80% power), 133 (90% power)
 75% of observed effect: n per arm = 176 (80% power), 235 (90% power)
 50% of observed effect: n per arm = 395 (80% power), 529 (90% power)
power.t.test: 99.6 
Simulated power at n = 99 per arm: 0.796 (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.

14. Multiplicity, Missing Data and Analysis Populations

The registry record does not report a multiplicity plan for the primary and secondary outcomes. It lists a primary endpoint and three secondary outcomes, but it does not say whether the secondary comparisons were prespecified as confirmatory, whether any hierarchy was planned, or whether adjustment for multiple testing was intended. The posted secondary p-values are unadjusted. Their interpretation should account for the possibility that examining multiple outcomes can produce apparently notable results by chance.

The record also reports no analyses in its analysis listing. It does not describe the statistical model, analysis population, handling of repeated measurements, or whether the primary comparison was the prespecified primary analysis. In particular, it does not report whether analyses followed an intention-to-treat principle, included participants with available measurements, or used another population definition. Those terms should not be assigned to the results without a stated definition.

Missing-data methods are not reported in the registry record. Although the enrollment is 32 and the posted treatment-condition summaries each list 19 participants, the record does not explain how these counts relate, identify missing outcomes, or describe imputation or other handling. The difference in counts should not be interpreted as a specific number of withdrawals or exclusions without participant-flow information.

For a crossover study, analysis details about participant pairing, sequence, visit period, and possible carryover can affect interpretation. The registry describes the interventions at the two visits but does not report how these issues were addressed statistically. It also does not report interim analyses or a detailed analysis plan. These absences leave important questions about the intended inferential framework unresolved; they do not establish that any particular procedure was or was not used outside the registry record.

15. 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.

For the oxytocin condition, the registry lists 32 participants at risk for serious adverse events and 0 affected. It also lists 32 at risk for other adverse events and 0 affected. The placebo condition likewise lists 32 at risk for serious adverse events and 0 affected, and 32 at risk for other adverse events and 0 affected. Deaths are listed as 0 in each condition, and no serious adverse-event terms are listed.

These figures describe what the registry reports for the recorded categories and denominators. They do not establish that no event of any kind occurred outside the categories or reporting period represented in the record. The registry does not provide additional detail about adverse-event collection, severity grading, exposure time, or how the crossover conditions were handled for safety reporting. The figures should therefore be read as the posted safety summaries, not as a complete characterization of risk.

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

The primary estimate describes a lower average duration of obstructive events in the oxytocin condition than in the placebo condition, with a mean difference of -1.94 seconds. The confidence interval extends from -5.032 to 1.152 seconds and includes zero. The posted result is therefore uncertain about the direction and magnitude of the difference. The unadjusted p-value of 0.219 is another summary of the data under a statistical model; it does not determine whether the difference is important or whether the treatments are equivalent.

The results concern measurements taken during the study visits. They do not show whether any observed contrast persists over time, changes symptoms, or affects longer-term cardiovascular outcomes. The registry’s rationale discusses potential cardiovascular benefits, but the posted primary endpoint is duration of obstructive events. The secondary measures provide related physiological observations, not a direct test of a broad cardiovascular benefit.

The registry describes a randomized crossover design, but it does not report whether the posted estimates account for the within-participant structure or other crossover-specific features. Nor does it report the original sample-size justification, the analysis population, missing-data handling, or a multiplicity plan. These gaps constrain interpretation of the recalculated summary comparisons. They do not support assumptions about how the original trial was analyzed.

The adverse-event summaries list zero affected participants for the serious and other adverse-event categories in both conditions, as well as zero deaths. Those counts are useful descriptions of the registry entries, but the record does not give enough detail to treat them as a complete assessment of safety or to generalize beyond the participants and reporting period.

In short, the posted data describe outcome averages and safety counts for this completed study. They do not by themselves provide a definitive answer about clinical benefit, equivalence, or broader risks. Interpreting them responsibly requires keeping the estimates, their uncertainty, the crossover design, and the missing analysis details in view.

17. Why This Trial Matters Statistically

This study illustrates a recurring statistical challenge in clinical research: a biologically motivated question can be broader than the primary outcome selected to measure it. The registry discusses potential cardiovascular effects of oxytocin in sleep apnea, while the primary endpoint is duration of obstructive events. Clear separation between the motivating hypothesis and the measured endpoint helps prevent an outcome-specific result from being stretched into a claim about an unmeasured clinical effect.

The crossover design also shows why design labels alone are not enough to interpret estimates. When participants receive both conditions, within-person information may be important to the comparison. The registry gives the treatment sequence at the visits, but does not report the analysis details needed to establish how pairing, visit period, or possible carryover were handled. A careful reader should distinguish the stated design from the analysis that can actually be verified in the record.

The primary estimate also demonstrates why point estimates, confidence intervals, and p-values answer different questions. The point estimate gives the direction and scale of the posted contrast; the interval conveys uncertainty; and the p-value summarizes compatibility with a null model under the calculation used. None alone determines clinical importance. The interval’s inclusion of zero is not evidence of equivalence, especially when no equivalence margin is reported.

Finally, the secondary outcomes and sample-size illustrations underline the importance of prespecification. Unadjusted secondary results are harder to weigh when no multiplicity plan is reported, and planning figures derived from an observed effect cannot serve as the original design rationale. These distinctions help readers separate descriptive evidence, exploratory patterns, and design assumptions that the record does not document.

18. 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.

A central limitation is that the registry record does not report the participant-level statistical analysis for this crossover study. The posted summary comparisons do not establish whether the analysis used paired observations or adjusted for visit period, sequence, or carryover. Those details matter because participants received both conditions at separate visits.

The posted outcome summaries list 19 participants per condition, while enrollment is 32. The record does not explain the relationship between these counts, provide participant flow, or report the reasons for unavailable outcomes, if any. Missing-data methods and analysis-population definitions are also not reported, limiting assessment of whether the summaries reflect all randomized participants or another set.

The record gives no original sample-size justification or detailed statistical analysis plan. The planning illustrations are based on observed effects and specified calculation assumptions, so they cannot clarify the reasoning behind the trial’s enrollment. The registry also does not report a multiplicity strategy for the secondary endpoints, which makes unadjusted secondary findings less conclusive.

The primary outcome is a physiological measure assessed at the two visits, not a long-term clinical outcome. The record does not report a threshold for clinical importance or an equivalence margin. In addition, the available safety summaries do not provide further detail about event collection or exposure periods. These limitations are specific to what is recorded for this trial; they should not be filled in by assuming procedures that are not reported.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Impact of Oxytocin on Obstructive Sleep Apnea Induced Changes in Sleep — NCT03148899.
• Registry record last updated 2023-01-31; status last verified 2023-01.
• Results first posted 2023-01-31.
• 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.

22. Record Summary

NCT03148899 is a completed Phase 2 randomized, triple-masked crossover study sponsored by George Washington University. It enrolled 32 participants with obstructive sleep apnea. The registry lists a start date of 2016-07-27 and a primary completion date of 2020-06-07.

Participants received oxytocin intranasal spray or placebo intranasal spray at Visit 1 and the opposite intervention at Visit 2. The primary outcome was duration of obstructive events in seconds, assessed on Visit 1 on Day 1 and Visit 2 on Day 29. The posted mean difference was -1.94 seconds, with a confidence interval from -5.032 to 1.152 seconds and an unadjusted p-value of 0.219.

Three secondary outcomes were posted: respiratory rate, incidence proportion of bradycardia, and minimum oxygen saturation. The record does not report a detailed analysis plan, missing-data methods, or multiplicity strategy. Serious adverse events, other adverse events, and deaths are each listed as 0 in both conditions.