Caregiver Self-Management of Stress: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Caregiver Self-Management of Stress (NCT04337021), a randomized na study. The primary outcome is 10-item Kessler Psychological Distress Scale (K10).

2. Clinical Question

The study asks whether Caregiver SOS, a phone-delivered self-management intervention for employed caregivers, changes caregiver distress and work performance and productivity compared with Usual Care. The primary outcome posted in the registry is psychological distress measured with the 10-item Kessler Psychological Distress Scale (K10) at 9 months. The registry describes higher K10 scores as indicating worse outcomes.

This is a question about a group-level difference in a continuous distress score. The registry’s study description also names work performance and productivity as aims, but the primary result is the K10. The record does not establish that a difference in this score necessarily corresponds to a particular change in work functioning, caregiving quality, or an individual participant’s experience.

3. Trial Design

The registry describes a randomized, parallel-group study with single masking. It lists 199 participants enrolled and identifies the study status as completed. The phase is recorded as NA. The sponsor is the VA Office of Research and Development. The study began on 2020-12-28, and the primary completion date is 2024-03-31.

Participants were assigned to Caregiver SOS or Usual Care. Caregiver SOS is described as a brief telephone intervention consisting of 6 one-hour sessions over 3-4 months. It focuses on self-management counseling for stress related to employment and caregiving. The intervention description names knowledge of work and caregiver stress and stress management among its behavior-change pillars; the available registry description does not give a complete account of all intervention components. Usual Care is described as a telephone contact with a care manager, a brief needs assessment, referral information for relevant VA and non-VA resources, and brochures for the national VA Caregiver Support Program.

The record calls the study single-masked but does not identify which people were masked. Details about how randomization was generated or implemented, concealment of assignment, and the trial’s original sample-size assumptions are not reported in the registry record. The total enrollment should not be treated as the number contributing to the primary outcome summaries: those summaries list 43 participants in Caregiver SOS and 48 in Usual Care. The record does not explain the difference between total enrollment and the outcome-specific group counts, so no reason for it can be inferred.

The primary outcome is the K10 score at 9 months. The record lists five outcome measures and five analyses, but the displayed primary outcome result is the continuous K10 summary. It also lists a sponsor analysis using a Chi-squared method, without enough detail to determine how that method relates to the continuous primary outcome summaries. The analysis population, handling of missing measurements, and detailed statistical plan are not reported in the registry record.

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 10-item Kessler Psychological Distress Scale (K10), measured over 9 months.

The primary endpoint is the mean score on the 10-item Kessler Psychological Distress Scale (K10) at 9 months. The registry describes the K10 as a global measure of psychological distress, with scores ranging from 10-50. Higher scores indicate worse outcomes, meaning higher levels of distress. The measure gives a continuous score that can be summarized by a group mean and standard deviation, allowing the average scores in the two randomized groups to be compared.

A standardized questionnaire is useful in a trial because it defines a consistent outcome for participants and provides a numerical summary for group comparisons. A mean difference expresses the contrast in the original score units, which makes the result interpretable in relation to the scale. A standard deviation describes how spread out participant scores are within a group; it does not describe the uncertainty in the group mean itself.

The K10 is the registry’s stated primary outcome, not a direct measure of every aim mentioned in the study description. The description also discusses work performance and productivity, caregiver wellbeing, and quality of care. The primary K10 result alone does not quantify those other outcomes. The registry record does not report a threshold for a clinically important K10 change or explain how a given score difference should be interpreted for an individual caregiver.

7. Results Posted in the Registry

• Caregiver SOS: mean 23.38 versus 23.79 on control; difference -0.41 (95% CI -3.61 to 2.79), standardized effect d = -0.05; z-test p = 0.802.

8. Statistical Interpretation

9. Statistical Methods Explained

The registry posts group means and standard deviations for the primary continuous outcome. A summary-statistic recalculation uses those group summaries to describe the unadjusted mean contrast. It is not the same thing as recovering the full trial analysis: individual participant data, covariate adjustments, and details of the sponsor’s model are not reported in the registry record.

What does a mean difference describe?

A mean is the arithmetic average of participant scores in a group. The mean difference compares the two group averages in the original outcome units. In this study, the contrast is defined as the Caregiver SOS mean minus the Usual Care mean. A negative result therefore indicates a lower mean K10 score in Caregiver SOS. Because the registry states that higher scores indicate worse outcomes, a negative contrast points toward lower average distress in that group. This direction should not be confused with evidence that the difference is precise or important.

A mean difference focuses on the center of each group’s score distribution. It does not show how individual scores overlap, whether every participant changed in the same direction, or how many participants experienced a particular degree of change. Group-level means can conceal varied participant experiences.

What do standard deviations add?

A standard deviation describes the spread of participant scores around a group mean. The posted standard deviations are 7.56 for Caregiver SOS and 8.03 for Usual Care. They help show that the outcome is variable across participants. A standard deviation is not a confidence interval and should not be read as a range containing a fixed proportion of the group without further assumptions about the score distribution.

The recalculation also reports a pooled standard deviation of 7.812. Pooling combines the groups’ variability into a common scale for describing a standardized contrast. The standardized effect, -0.052, expresses the mean difference in relation to that pooled variability. This can help compare effects measured on different scales, but it is less directly interpretable than the difference in K10 points. A small standardized contrast does not establish that an outcome is unimportant, and the registry does not provide a threshold for interpreting clinical importance.

How should the confidence interval and p-value be read?

A confidence interval expresses uncertainty around an estimated contrast under the assumptions of the analysis used to construct it. The reported interval runs from -3.614 to 2.794. It includes zero, the value corresponding to no mean difference, and extends to both negative and positive contrasts. Its span indicates that the estimate is not precise enough to settle the direction of the group difference based on this recalculation alone. The confidence level and exact calculation method are not reported in the registry record.

The unadjusted p-value is 0.802. In general, a p-value measures how compatible the observed data are with a specified null model, under the assumptions of the test. It is not the probability that the null hypothesis is true, nor the probability that the result occurred by chance. The recalculation is identified as unadjusted; the exact test procedure used for it is not reported in the registry record. The p-value should be considered alongside the estimated difference and its confidence interval rather than used as a stand-alone verdict.

Over-dispersion is a general concern when a statistical model assumes less variability than the data contain. If actual variation is greater than the model allows, standard errors may be too small and uncertainty may be understated. The posted primary summaries include group standard deviations, but the registry record does not describe a model-based over-dispersion assessment. There is no basis in the record to claim that over-dispersion was present or that a particular correction was applied.

How does the sponsor analysis differ?

The registry lists a sponsor analysis with method Chi-squared and p = 0.513. A Chi-squared procedure is generally used for categorical data or for comparing observed counts with expected counts under a model. The primary outcome summarized in the registry is a continuous K10 mean. Since the record does not specify which endpoint or data were entered into the sponsor analysis, it is not possible to reconcile that test with the continuous mean comparison. The sponsor’s reported result and the unadjusted recalculation should therefore be described separately.

The reported sponsor analysis is labelled superiority, but the registry does not provide an effect estimate or confidence interval for it. The label does not supply the missing detail about the tested outcome or analysis population. The record also does not state whether the sponsor analysis adjusted for baseline values, other covariates, clustering, or multiplicity. Those features should not be assumed.

What does randomization contribute?

Random assignment is intended to create comparison groups whose characteristics are balanced on average, including characteristics that may not be measured. That is the general rationale for randomized designs. The registry identifies allocation as randomized, but it does not report the sequence-generation or allocation-concealment procedures. The posted group summaries alone cannot demonstrate that every characteristic was balanced or explain how any imbalance was addressed.

The main statistical distinction is between the observed estimate and the uncertainty around it. The mean difference is the estimate; the interval describes its uncertainty under the stated analysis assumptions. A p-value provides a related test against a null model, but it does not replace the effect estimate or its interval. In this record, those pieces support a cautious description of the observed group contrast, not a definitive claim about benefit, lack of benefit, or equivalence.

10. Confidence Intervals and Precision

The recalculated mean difference is -0.41 K10 points, with a confidence interval from -3.614 to 2.794. The interval includes zero and extends in both directions. It therefore does not pinpoint a single direction or a narrow range of plausible contrasts. The estimate leans toward a lower mean score in Caregiver SOS, but the uncertainty includes a higher mean score as well.

Precision depends on how much information the outcome data contain, including the number of observations and the variability of scores. The primary summaries list 43 participants in Caregiver SOS and 48 in Usual Care, with standard deviations of 7.56 and 8.03, respectively. The registry lists total enrollment as 199, but it does not explain why the outcome-specific counts are different from total enrollment. Reasons for the difference, including missing outcome measurements or exclusions, are not reported in the registry record.

The confidence level for the interval and the exact method used to calculate it are not reported in the registry record. The interval should therefore be interpreted as the displayed uncertainty estimate without adding an assumed confidence level. Its width matters: it allows a range of contrasts rather than establishing that the true difference is exactly the observed mean difference.

The interval is not a range of individual participant scores, and it does not predict the outcome for a particular caregiver. Nor does including zero show that the groups are equivalent. A claim of equivalence would require a prespecified margin and an appropriate analysis, neither of which is reported in the registry record. The interval is most useful when read together with the scale direction, group means, and the limits of the posted analysis.

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 planning illustrations based on fractions of the observed effect, not the trial’s original design calculations. They give participants per arm for 80% power and participants per arm for 90% power. They are not total events: the registry’s planning assumptions specify participants per arm for this continuous outcome. The record’s original design assumptions are not reported in the registry record.

The 80% power column describes an illustrative design that would have an 80% probability of detecting the specified effect under the stated assumptions, if that effect were the true effect and the assumptions held. The 90% power column uses a higher target probability of detecting the specified effect, so it requires a larger planned sample under the same assumptions. These figures are design calculations, not a measure of the probability that the observed result is correct.

The rows use 100%, 75%, and 50% of the observed effect as planning targets. Smaller effects require more participants because a smaller group difference is harder to distinguish from outcome variability. The listed participant counts rise as the target effect becomes a smaller fraction of the observed effect. Because the observed mean difference is close to zero, the planning figures based on it are very large; they should be understood as illustrations tied to that estimate, not as recommended enrollment targets or as evidence about what the trial was designed to detect.

The listed assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The target effect is the stated fraction of the observed effect. The registry does not report whether the original trial used these assumptions. This is not observed power: it is a prospective-style calculation using the posted effect estimate, and it does not measure the study’s actual ability to detect an effect after the results are known.

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 = -0.410; pooled standard deviation σ = 7.812.
2. n = 2 × (1.96 + 0.842)² × 7.812² / -0.410² = 5,698.5, rounded up to 5,699 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 <- -0.41                      # observed difference in means
sigma <- 7.81172663587941                     # 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(4337021)
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 = 5,699 (80% power), 7,629 (90% power)
 75% of observed effect: n per arm = 10,131 (80% power), 13,563 (90% power)
 50% of observed effect: n per arm = 22,795 (80% power), 30,515 (90% power)
power.t.test: 5699.5 
Simulated power at n = 5,699 per arm: 0.800 (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. Analyses Reported by the Sponsor

The registry lists the sponsor’s analysis as a Chi-squared superiority analysis with p = 0.513. The record does not give a test statistic, effect estimate, confidence interval, or sufficient detail about the outcome analyzed. In particular, it does not establish that this analysis tests the posted continuous K10 mean difference. Its result should be reported as the sponsor analysis recorded in the registry rather than interpreted as a direct alternative calculation of the mean contrast.

The separate summary-statistic recalculation compares the posted K10 group means and dispersions without adjustment. It estimates a mean difference of -0.41, with a confidence interval from -3.614 to 2.794 and an unadjusted p-value of 0.802. It is a simple comparison based on the registry summaries, not a replacement for a fuller sponsor analysis using participant-level data or a specified model.

There is no discrepancy flag for these results, so the record does not identify a conflict that would displace the sponsor’s own analysis. Even so, the sponsor analysis and recalculation cannot be reconciled from the available details because their relationship is not reported in the registry record. They should remain distinct: one is the sponsor’s reported Chi-squared result; the other is an unadjusted mean comparison derived from the posted continuous summaries. No conclusion about why the p-values differ can be made from the registry information.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures and five analyses, but the record does not report a multiplicity strategy. Multiplicity arises when several outcomes, comparisons, or analyses are examined: the more opportunities there are to find a result that appears unusual under a null model, the more important it becomes to understand whether and how the analysis accounted for that structure. This general issue does not establish that any particular finding is a false positive. Without a stated adjustment or hierarchy, the reader cannot tell whether the posted tests were intended to be interpreted individually or as a family.

The registry identifies the K10 at 9 months as the primary outcome. It also states that the study aimed to examine work performance and productivity. However, secondary results are not posted in the registry record. The relationship between the five listed outcome measures, the five analyses, and the specific sponsor Chi-squared analysis is not explained in sufficient detail to reconstruct an analysis hierarchy or determine which comparisons were included in any multiplicity procedure.

The record does not describe the analysis population for the primary outcome. It does not state whether the results follow an intention-to-treat approach, a per-protocol approach, or another population definition. Such labels should not be assigned based only on the randomized design. The outcome summaries report 43 participants in Caregiver SOS and 48 in Usual Care, while total enrollment is 199; the record does not explain the difference.

Missing-data methods are not reported in the registry record. There is no description of the amount or pattern of missing K10 data, assumptions used for missing outcomes, imputation, sensitivity analyses, or handling of withdrawals. The outcome-specific counts alone do not show why participants are absent from the summaries or whether missingness could affect the contrast.

Other analysis details are also not reported in the registry record, including baseline adjustment, the exact method for the recalculated confidence interval, and whether the sponsor’s analysis included covariates. These omissions limit independent assessment of the analysis and how robust the results may be to alternative assumptions. They do not, by themselves, show that an analysis was inappropriate; they mark questions that the registry information does not answer.

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.

The registry lists serious adverse events for 99 participants at risk in Caregiver SOS and 100 at risk in Usual Care. It reports 0 participants with serious adverse events in each group. For other adverse events, it likewise lists 99 and 100 participants at risk, with 0 affected participants in each group. Deaths are recorded as 0 in both groups.

These are the counts recorded in the registry, not a complete description of every safety event or the way events were collected and assessed. The registry does not list serious adverse event terms, and it does not provide further information about event definitions, monitoring, duration of follow-up, severity grading, or causal attribution. Zero affected participants in the posted counts means no events were recorded in those categories for the listed groups; it does not establish that no event could occur or that there was no safety risk.

The safety counts use groups of 99 and 100 at risk, whereas the primary K10 summaries include 43 and 48 participants. The registry record does not explain the different denominators, so they should not be treated as interchangeable or used to infer why participants contributed to one result but not another. The adverse-event figures describe the registry’s recorded safety summary and do not resolve the unreported details of safety monitoring.

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

The primary result describes average K10 scores at 9 months among the participants represented in the posted summaries. The Caregiver SOS mean is 23.38, compared with 23.79 for Usual Care. Since higher scores indicate worse outcomes, the observed difference points toward a lower average distress score in Caregiver SOS. The recalculated contrast is -0.41 points, with a confidence interval from -3.614 to 2.794 and an unadjusted p-value of 0.802.

The result does not establish a clear group difference, but it also does not establish equivalence or prove that the intervention had no effect. The interval includes zero and allows contrasts in either direction. The registry does not report an equivalence margin or a threshold for a clinically important K10 change. Accordingly, neither a claim of meaningful improvement nor a claim of no meaningful effect follows from this result alone.

The outcome is a group-level measure of psychological distress. It does not report how individual participants changed from baseline, whether every participant experienced the same direction of change, or how the score relates to each caregiver’s work situation. The primary result also cannot answer the study’s broader questions about work performance, productivity, caregiver wellbeing beyond the K10, or quality of care. Those outcomes would require their own posted results, which are not reported in the registry record.

The sponsor’s Chi-squared result is listed separately, with p = 0.513, but its relationship to the continuous K10 summaries is not reported in the registry record. It should not be used to strengthen or overturn the recalculated mean comparison without knowing what outcome and analysis it represents. More generally, a p-value is not a measure of clinical importance, and the observed result is not an individual prediction.

The appropriate reading is limited: the posted K10 summaries show similar group means, with an uncertain unadjusted estimate of their difference. The available information does not support a definitive statement about the intervention’s effect on distress, and it does not address all outcomes named in the study description.

17. Why This Trial Matters Statistically

This trial raises a statistical question that is common in behavioral intervention research: how to interpret a modest group-level contrast when participant scores vary substantially. The means are close, while the standard deviations are 7.56 and 8.03. Considering the difference alongside score variability and the confidence interval is more informative than relying on a single p-value. The contrast is estimated in the original K10 units, and the interval communicates that the estimate remains uncertain.

The record also illustrates why the identity of the tested outcome and analysis matters. The primary endpoint is a continuous distress score, but the sponsor analysis is labeled Chi-squared. Without details connecting that analysis to the K10 summaries, the two results cannot be treated as if they were estimates from the same statistical procedure. Clear reporting of the endpoint, analysis population, model, effect estimate, and uncertainty would make the relationship easier to assess.

There is a practical distinction between a trial’s original design and planning calculations made after observing its results. The planning figures use fractions of the observed effect and stated assumptions. They can show how a smaller target contrast requires more participants, but they do not tell readers what effect the study was originally designed to detect. That original design information is not reported in the registry record.

Finally, the difference between total enrollment and the outcome-specific counts, alongside unreported missing-data methods and analysis populations, highlights the importance of participant flow and outcome completeness. These details affect how readers understand which participants contribute to an estimate. The registry’s summary supports a cautious statistical interpretation, while leaving important methodological questions unresolved.

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 provides limited detail for interpreting the primary outcome analysis. It does not report the confidence level or exact calculation method for the displayed confidence interval, nor does it describe the test used for the unadjusted recalculation. The sponsor’s Chi-squared analysis lacks an effect estimate, test statistic, and explanation of its relationship to the continuous K10 outcome. These gaps prevent a full reconciliation of the two results.

The primary summaries include 43 participants in Caregiver SOS and 48 in Usual Care, while enrollment is 199. The registry does not explain the outcome-specific counts, report participant flow, or describe the analysis population. Missing-data amounts, patterns, assumptions, and sensitivity analyses are also not reported in the registry record. The effect of any missing outcomes on the result therefore cannot be assessed from the posted summaries.

The record does not state whether the analysis adjusted for baseline K10 scores or other participant characteristics. It does not report the original sample-size justification, detailed randomization procedures, or which people were masked despite the single-masking designation. The protocol’s full statistical plan and any interim analyses are not reported in the registry record.

The registry lists five outcome measures and five analyses but does not describe how they relate or whether multiplicity was addressed. Secondary results are not posted. As a result, the primary K10 summary does not provide a complete account of the outcomes named in the study description, including work performance and productivity.

The intervention descriptions in the record are incomplete. The SOS description gives its session schedule and some content, but not all listed behavior-change pillars; the Usual Care description also ends without a complete account. The record does not report a threshold for clinically important K10 change. These limitations constrain interpretation of the intervention contrast, the completeness of outcomes, and the practical meaning of the score difference.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Caregiver Self-Management of Stress — NCT04337021.
• Registry record last updated 2025-11-18; status last verified 2025-11.
• Results first posted 2025-11-18.
• 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

NCT04337021, titled Caregiver Self-Management of Stress, is a completed randomized, parallel-group study with single masking and enrollment of 199. It compares telephone-delivered Caregiver SOS with Usual Care for employed informal caregivers. The sponsor is the VA Office of Research and Development.

The primary endpoint is the K10 psychological-distress score at 9 months, where higher scores indicate worse outcomes. The posted means are 23.38 for Caregiver SOS and 23.79 for Usual Care. The unadjusted recalculated mean difference is -0.41, with a confidence interval from -3.614 to 2.794 and p = 0.802. The sponsor analysis is separately listed as a Chi-squared superiority analysis with p = 0.513; its relationship to the continuous K10 contrast is not reported in the registry record.

The primary summaries do not establish a clear group difference, and the uncertainty does not establish equivalence. Details about missing data, analysis populations, multiplicity, and the trial’s original sample-size assumptions are not reported in the registry record. The posted safety counts list no serious or other adverse events and no deaths in either group.