Mindfulness and Yoga for Pain With Interstitial Cystitis Evaluation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Mindfulness and Yoga for Pain With Interstitial Cystitis Evaluation (NCT04820855), a randomized na study. The primary outcome is Number of Participants Designated as "Treatment Responders" Based on Global Response Assessment (GRA).

2. Clinical Question

The comparison concerns a structured behavioral program alongside the usual-care comparison, not yoga or mindfulness in isolation. The registry describes the study as examining pain’s impact on daily life, ability to function, and treatments used before and after the program. Its posted primary outcome is narrower: a count of participants meeting the GRA response definition at the stated follow-up.

The registry record does not report further eligibility details in the outcome information. It also does not report the exact content or frequency of usual provider care, or whether participants could receive other treatments during follow-up. Those details would help clarify how closely the groups’ care differed beyond the listed program.

3. Trial Design

The registry describes a randomized, single-masked, parallel-group study. It lists the status as completed, the sponsor as the University of New Mexico, the start date as 2021-05-18, and primary completion as 2023-09-30. The registry lists enrollment of 97. The phase is recorded as NA.

In a randomized parallel design, participants are assigned to groups that are followed over the same study period. Random allocation is intended to support a fair comparison by reducing systematic differences at assignment, although it does not ensure that the groups are identical in every respect. The registry does not report the sequence-generation method, allocation concealment, or who was masked. “Single” therefore describes the masking designation but does not establish which people were masked.

The treatment group received an individual program devised by a pelvic floor physical therapist, with daily yoga and mindfulness using a smartphone app. The control group received regular treatment for interstitial cystitis with their providers. The primary outcome timeframe is 3 months, and the response definition refers to the GRA at 12 weeks.

For the primary outcome, the posted arm summaries include 43 participants in Treatment and 39 in Control. The registry record does not report how these outcome denominators relate to the enrollment figure, participant flow after randomization, or the number who completed follow-up. It does not report the original target sample size, the design assumptions behind that target, or whether the analysis followed an intention-to-treat approach. These omissions limit assessment of recruitment and follow-up, but do not change the meaning of the arm-specific results as posted.

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.

Overall Study

Reasons for not completing this period:

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 Number of Participants Designated as "Treatment Responders" Based on Global Response Assessment (GRA), measured over 3 months.

The primary endpoint is the number of participants designated “Treatment Responders” based on the Global Response Assessment. The registry describes the GRA as a validated single question and defines a responder as someone who answered “markedly improved/moderately improved” at 12 weeks. The endpoint is reported at the 3 months timeframe.

This is a binary outcome at the participant level: each person either meets the stated responder definition or does not. Summarizing it as a count makes the number of responders visible, while comparing that count in relation to each group’s reported outcome denominator allows the response proportions to be compared. The registry’s reported treatment effect is expressed as a risk difference, the difference between those proportions.

A global assessment can capture a participant’s overall judgment of change rather than a single symptom score. That can complement measures focused on symptoms, pain, or function. At the same time, a one-question assessment depends on the participant’s interpretation of improvement and on the chosen response categories. The registry record does not report the wording of the full question, how responses outside the two specified improvement categories were handled, or whether the responder threshold was selected before results were examined. The result therefore describes the posted operational definition, not every possible meaning of improvement.

7. Results Posted in the Registry

• Treatment: 72.1% (31/43) versus 25.6% (10/39) on control; risk difference 46.5 percentage points (95% CI 27.3 to 65.6), risk ratio 2.81 (1.60–4.95); unadjusted two-proportion z-test p = <0.001.

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.

O'Leary-Sant: Interstitial Cystitis Symptom Index

• 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:
  • Treatment: mean -3.40 versus -1.50 on control; difference -1.90 (95% CI -3.55 to -0.25), standardized effect d = -0.50; z-test p = 0.024.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Treatment than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

O'Leary-Sant: Interstitial Cystitis Problem Index

• 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:
  • Treatment: mean -3.70 versus -1.90 on control; difference -1.80 (95% CI -3.10 to -0.50), standardized effect d = -0.60; z-test p = 0.007.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Treatment than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Pain VAS Score

• 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:
  • Treatment: mean -1.70 versus -0.30 on control; difference -1.40 (95% CI -2.42 to -0.38), standardized effect d = -0.59; z-test p = 0.007.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Treatment than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The numerical secondary results available for interpretation cover symptom burden, problems attributed to interstitial cystitis, and pain on a visual analogue scale. Across these outcomes, the mean changes are more negative in Treatment than in Control, and the unadjusted mean-difference intervals exclude zero. This pattern is directionally consistent with the primary comparison’s higher responder proportion in Treatment, but the outcomes measure different aspects of participants’ experience and use different scales.

The secondary findings add context rather than replacing the primary endpoint. A global response is a participant-level classification, whereas score changes describe average movement on separate scales. Agreement across outcome types can make a pattern more coherent, but it does not establish that every listed symptom or functional domain changed in the same way. The registry lists seven secondary outcome measures; numerical comparative details for the remaining listed outcomes are not reported in the registry record.

All listed secondary comparisons are unadjusted. When several outcomes are examined, the chance of observing at least one small p-value by chance can increase. Without a reported multiplicity plan, the secondary p-values are best treated as exploratory evidence rather than definitive tests. Their interpretation also depends on prespecification, missing-data handling, and the meaning of change on each scale, none of which is fully described in the registry record.

The registry summary says the study examines daily-life impact, function, and treatments used, but the numerical secondary results do not provide a complete account of those domains. Results for the other listed measures and the analysis details needed to assess them are not reported in the registry record. The overall pattern is therefore supportive context for the posted primary comparison, with uncertainty about breadth and reproducibility.

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

• O'Leary-Sant: Interstitial Cystitis Symptom Index
• O'Leary-Sant: Interstitial Cystitis Problem Index
• Pain VAS Score
• Hospital Anxiety and Depression Scale (HADS) Anxiety Subscale
• Hospital Anxiety and Depression Scale (HADS) Depression Subscale
• PROMIS Pain Interference Score
• Pain Self-efficacy-2 Score

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is binary because the GRA definition divides participants into responders and nonresponders. The arm summaries give the responder count and the number of participants contributing to that outcome. Dividing the count by its denominator yields a response proportion; comparing the two proportions gives the risk difference. The posted risk difference is 0.465. A positive difference means the proportion is higher in Treatment than in Control, given the registry’s group order and definition.

In general, a risk difference is an absolute contrast. It is often straightforward to interpret because it describes how far apart the group probabilities are on the probability scale. The risk ratio instead expresses one group’s probability relative to the other group’s probability. The odds ratio compares odds, where odds are the probability of an event relative to the probability of no event. Risk ratios and odds ratios can be useful complementary summaries, but they are not interchangeable with an absolute difference. The posted estimates are 2.812 for the risk ratio and 7.492 for the odds ratio; each describes the same responder outcome using a different scale.

A confidence interval gives a range of values compatible with the data and the interval procedure, subject to the model and calculation assumptions. For the risk difference, the posted interval runs from 0.273 to 0.656. Because this interval lies above zero, it is consistent with a positive difference under the calculation used. An interval does not account automatically for every design issue, such as missing outcomes, unblinded assessment, or selection of outcomes after seeing results. The registry record does not report the confidence-interval method or its nominal coverage level.

The p-value is another summary, but it answers a different question from the interval. In general, it measures how unusual results at least as extreme as the observed result would be under a specified no-difference model and its assumptions. The primary unadjusted p-value is <0.001. It is not the probability that the null hypothesis is true, and it does not quantify the size or importance of the difference. The registry record does not report the sponsor’s analysis method for this test.

The secondary outcomes are continuous scores reported as mean changes from baseline to 3 months, with standard deviations. A mean change describes the average score movement in a group; the mean difference compares those group averages. The posted mean differences for the three secondary outcomes are on their respective score scales. Negative change values mean the recorded scores declined from baseline; whether that direction is clinically favorable depends on scale interpretation, which is not fully described in the registry record.

In general, a standard deviation describes how spread out individual observations are around the group mean. It is not the same as a confidence interval and does not directly give the precision of the estimated mean. Precision also depends on the number of observations and the analysis model. The registry record reports standard deviations for the three continuous outcomes, but does not report participant-level data, the method used to handle missing scores, or adjusted estimates.

The unadjusted mean difference is a direct comparison of the group means as reported, without accounting for other variables. For these secondary outcomes, the posted intervals and p-values are likewise unadjusted. Adjustment for baseline characteristics can change an estimate and its uncertainty, but whether an adjusted model was planned or conducted is not reported in the registry record. No sponsor-reported analyses are listed for the secondary outcomes.

Over-dispersion is a general concern when a statistical model assumes less variability than the data actually contain. In binary outcomes, for example, clustering or other dependence can make observations less independent than a simple model assumes. If that is not accounted for, uncertainty may be understated. The registry record does not report a model-based adjustment for clustering or other over-dispersion, nor does it report evidence that either was present in this study; this is a general consideration rather than a claim about the trial.

Random allocation and a parallel-group comparison define the design, but the registry record does not give the detailed statistical plan. The handling of repeated measurements, the primary analysis population, missing-data methods, covariate adjustment, and any interim analyses are not reported in the registry record. Without those details, the posted summary comparisons can be interpreted descriptively and statistically on their stated scales, but not as a complete account of the trial’s analysis process.

11. Confidence Intervals and Precision

The primary risk-difference interval extends from 0.273 to 0.656, with the point estimate at 0.465. Its limits indicate that the observed data are compatible with a range of positive differences under the interval method used. The interval excludes zero, while the unadjusted p-value is <0.001. Together, these statistics indicate evidence of a difference in the posted comparison, but they do not remove uncertainty about its size or address possible bias from outcome collection, missingness, or analysis choices.

The relative-scale intervals also exclude their no-difference value: the risk-ratio interval is 1.597 to 4.951, and the odds-ratio interval is 2.811 to 19.96. Their widths show that the relative effects are not estimated with pinpoint precision. Relative measures can also appear large when the underlying event probabilities are not large, so the absolute risk difference and the group proportions are important context.

The three continuous-outcome mean-difference intervals are -3.55 to -0.250 for the Symptom Index, -3.099 to -0.501 for the Problem Index, and -2.418 to -0.382 for Pain VAS. Each interval excludes zero, though their endpoints span a range of possible mean contrasts. Their scales differ, so the interval widths should not be compared as if they measured the same quantity. The registry record does not report thresholds for interpreting the clinical importance of these score differences.

Confidence intervals describe sampling uncertainty under a specified calculation; they do not include all uncertainty about how participants were selected, whether outcomes were missing, or whether the model was appropriate. The record does not report the interval procedure, missing-data methods, or detailed analysis populations. Precision should therefore be read alongside these limits, rather than as a guarantee about the range of effects in other settings.

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 planning figures are participants per arm for 80% power and participants per arm for 90% power. These are not total sample sizes and are not total event counts; the listed outcomes are not time-to-event outcomes. The 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 the stated fraction of the observed effect.

The 80% power column gives the planned per-arm size under which the calculation has an 80% probability of detecting the specified effect if that effect is the true one and the assumptions hold. The 90% column uses a higher target probability of detection under those same assumptions. These percentages describe the design calculation, not the chance that the observed result is correct. Smaller target effects require more participants to distinguish them from random variation, which is why planning for a smaller fraction of the observed effect leads to larger per-arm figures.

Each planning row is anchored to the observed effect at a different fraction, so the figures should be treated as illustrations of how sample requirements depend on the effect size chosen. An observed estimate is uncertain, and using it as the basis for planning can yield estimates that are optimistic if the observed effect is larger than the effect a future study should be designed to detect. The figures do not reconstruct the study’s original design. The trial’s original sample-size assumptions and justification are not reported in the registry record. 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, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.256; treatment proportion p₁ = 0.721; average p̄ = 0.489.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.7069 = 1.3855.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6260 = 0.5268.
4. n = (1.3855 + 0.5268)² / (0.4645)² = 16.9, rounded up to 17 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
p0 <- 0.256410256410256                          # control proportion
p1 <- 0.720930232558139                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^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 (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(4820855)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 17 (80% power), 23 (90% power)
 75% of observed effect: n per arm = 31 (80% power), 41 (90% power)
 50% of observed effect: n per arm = 67 (80% power), 89 (90% power)
power.prop.test: 16.9 
Simulated power at n = 17 per arm: 0.824 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-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 lists a primary outcome and seven secondary outcome measures. It does not report a multiplicity strategy, such as a hierarchy of tests or an adjustment to account for testing several outcomes. The posted secondary p-values are unadjusted. When multiple hypotheses are tested, the probability of at least one apparently notable result arising by chance can increase; this general issue makes unadjusted secondary findings less conclusive than a prespecified primary comparison.

The registry record does not report whether all listed outcomes were prespecified in the same way, whether analyses were changed after enrollment, or whether interim analyses were conducted. The statistical analysis plan is not reported in the registry record. No sponsor-reported analyses are listed for the outcomes. These omissions prevent a full assessment of which analyses were planned in advance and how the reported comparisons relate to those plans.

Missing-data handling is also not reported in the registry record. The primary outcome summaries use arm-specific denominators of 43 and 39, while the registry lists enrollment of 97. The record does not explain participant flow, the outcome status of those not represented in these denominators, reasons for missing outcomes, or whether any imputation or sensitivity analysis was used. The denominators should therefore be read as the counts associated with the posted outcome summaries, not as evidence about how missing observations were handled.

The analysis population is not reported in the registry record. It is not stated whether the primary comparison included everyone as randomized, only participants with observed outcomes, or another defined group. The randomization method and allocation concealment are also not reported. These gaps matter because exclusions or missing outcomes after randomization can weaken the protection randomization is intended to provide. They do not establish that bias occurred, but they limit the ability to evaluate it from 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.

Most frequent non-serious adverse event terms

For serious adverse events, the registry reports 0 affected participants in Treatment among 49 at risk and 0 in Control among 48 at risk. No serious adverse event terms are listed. For other adverse events, it reports 1 affected participant among 49 at risk in Treatment and 0 among 48 at risk in Control. Deaths are reported as 0 in both groups.

These are counts within the safety groups and should be read separately from the primary-outcome denominators. The record does not explain why the safety group sizes differ from the outcome group sizes, how events were collected, or the period over which participants were monitored. A zero count means no events of the specified category were recorded in the listed group; it does not establish that the risk is absent. The registry record does not provide event descriptions for the single other adverse event.

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

The primary result describes a higher observed proportion of participants meeting the registry’s GRA responder definition in Treatment than in Control at 12 weeks. The risk-difference interval is entirely above zero, and the unadjusted p-value is <0.001. In statistical terms, the posted comparison is inconsistent with a no-difference model at conventional thresholds, given the calculation and assumptions used. The result is an estimate with uncertainty, not a precise guarantee of the effect size.

The finding applies to the responder definition, the enrolled study groups, and the reported follow-up. It does not show which element of the program produced the difference: the intervention combines a therapist-devised program, daily yoga, and mindfulness through a smartphone app. Nor does the result establish that the difference persists after the 3 months timeframe. Longer-term outcomes are not reported in the registry record.

The result should not be taken as proof that every participant experienced improvement, or that every symptom and functional measure changed in the same way. The secondary summaries provide additional but unadjusted evidence, and several listed secondary outcomes lack numerical results in the registry record. No threshold for a clinically meaningful change is reported, so statistical evidence alone cannot determine the practical importance of the estimates.

Randomization is a strength for comparing groups, but interpretation also depends on implementation and analysis. The record does not identify who was masked, explain participant flow or missing data, or provide the analysis plan. These absences do not show that the study was conducted improperly; they mean that readers cannot assess those features from the registry record. The result is a posted trial comparison, not an individual prediction or treatment recommendation.

17. Why This Trial Matters Statistically

This trial illustrates how a behavioral program can be evaluated with both a global participant response and continuous symptom-related scores. The primary endpoint is not simply a change in an average score: it classifies participants using a stated response threshold. That distinction affects what the estimated risk difference means and why the responder definition should be read closely.

The record also illustrates the value of presenting absolute and relative measures for a binary endpoint. The risk difference communicates the separation in response proportions, while the risk ratio and odds ratio express relative contrasts. Their intervals add information about precision that a p-value alone cannot convey. Presenting changes and standard deviations for continuous outcomes offers a complementary view, while highlighting that scale interpretation and meaningful-change thresholds are necessary for clinical context.

At the same time, the registry record shows why a statistically notable result is not the whole analysis story. Reporting of missingness, analysis populations, multiplicity, masking, and the statistical plan affects how confidently readers can evaluate the comparison. Secondary results can reinforce a coherent pattern, but unadjusted testing across multiple outcomes carries more uncertainty. The absence of analysis details should be distinguished from evidence that a particular method was or was not used.

The posted sample-size illustrations show the dependence of planning requirements on the effect chosen for detection. They are not a substitute for the trial’s design justification, which is not reported in the registry record. Overall, the study is a useful example of interpreting a randomized comparison through outcome definition, effect scale, precision, and reporting completeness together rather than relying on a single test statistic.

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.

The registry record gives limited detail about trial conduct. Although the design is labeled randomized and single-masked, it does not report the randomization procedure, allocation concealment, or who was masked. The intervention includes several components, while the usual-care description is broad; the record does not provide enough detail to separate their contributions or characterize treatment received during follow-up.

Participant flow and analysis populations are not described. The listed enrollment and the primary outcome denominators do not have an accompanying explanation of exclusions, withdrawals, or missing outcomes. Missing-data methods and sensitivity analyses are not reported in the registry record. These gaps make it difficult to assess whether the posted outcome summaries represent the randomized groups in a comparable way.

The primary outcome depends on a self-reported global assessment and a responder threshold. The record describes the improvement categories used but does not report the full question wording or how other response categories were handled. A clinically meaningful threshold for the continuous scores is also not reported. Thus the statistical contrasts are interpretable on their posted scales, but their practical significance is harder to judge.

The secondary outcomes are subject to multiplicity concerns because no adjustment strategy is reported. Numerical results for several listed secondary measures are not reported in the registry record. The analysis plan, original sample-size rationale, and interim-analysis information are also not reported. These limitations concern the available record; they do not by themselves establish that bias, inappropriate analysis, or a harmful event occurred.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Mindfulness and Yoga for Pain With Interstitial Cystitis Evaluation — NCT04820855.
• Registry record last updated 2025-03-05; status last verified 2025-02.
• Results first posted 2025-03-05.
• 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

The registry identifies NCT04820855 as a completed randomized, single-masked, parallel study sponsored by the University of New Mexico, with enrollment listed as 97. It compared an individual pelvic-floor-therapist-devised program involving daily yoga and app-based mindfulness with regular provider treatment for interstitial cystitis.

The primary outcome was the number of GRA treatment responders at 12 weeks. Posted results report 31 responders among 43 in Treatment and 10 among 39 in Control, with an unadjusted risk difference of 0.465 and an interval from 0.273 to 0.656. Three secondary outcomes have numerical comparative results; the registry record does not report a multiplicity plan, analysis populations, missing-data methods, or the sponsor’s statistical analysis plan.