Staying Active With Arthritis: RCT of Physical Activity for Older Adults With Osteoarthritis and Hypertension: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Staying Active With Arthritis: RCT of Physical Activity for Older Adults With Osteoarthritis and Hypertension (NCT01280903), a randomized na study. The primary outcome is Performance of Lower Extremity Exercise at 25 Weeks.

2. Clinical Question

3. Trial Design

The registry record describes a randomized, parallel-group behavioral trial with single masking. It lists the STAR Intervention and the Attention-Control intervention as the two arms. The record identifies the latter as the Senior Health Information Intervention. It does not state who was masked, so the masking label cannot establish whether participants, intervention staff, outcome assessors, or another group were unaware of assignment.

The trial enrolled 182 participants. The posted primary outcome summaries list 91 participants in each arm. The record identifies the study population as older adults with knee osteoarthritis and hypertension, but detailed inclusion and exclusion criteria are not reported in the registry record. The record lists the study status as completed, with a start of 2012-01 and primary completion of 2015-04. The sponsor is the University of Pittsburgh. The phase is listed as NA.

The study’s stated purpose was to determine whether a 6-month program would affect physical activity and clinical outcomes. The primary endpoint was lower-extremity exercise performance at week 25. The record also describes fitness walking and a range of clinical outcomes as study interests. The posted record includes secondary outcomes at week 25 for subjective functional status, quadriceps strength, pain, fatigue, health-related quality of life, self-efficacy, and arthritis self-efficacy.

The study is labeled randomized, but the randomization sequence, allocation concealment procedures, and any stratification factors are not reported in the registry record. The protocol’s original sample-size assumptions and the intended analysis population are also not reported in the registry record. These omissions limit assessment of how the design and analysis were planned, even though the arm-level outcome summaries and the sponsor’s reported analysis are available for the primary endpoint.

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 Performance of Lower Extremity Exercise at 25 Weeks, measured over At the end of the 6-month intervention period (week 25).

The primary endpoint is performance of lower-extremity exercise at week 25, at the end of the 6-month intervention period. It is measured as total exercise volume over a 7-day period, expressed in repetitions multiplied by sets per week. The registry description says the measure incorporates the days on which a participant reports completing a lower-extremity exercise session and the total number of lower-extremity exercises performed per day.

This endpoint focuses on reported exercise behavior rather than a clinical event or a direct measure of physical capacity. It is relevant to the stated goal of promoting physical activity: it records whether exercise sessions were reported and how much exercise was completed. The measure is based on an electronic diary, so it represents diary-recorded activity and should be interpreted as such. The registry does not report details about diary completion, validation, or how missing diary entries were handled.

The arm summaries report means and standard errors. The STAR mean was 46.84 repetitions multiplied by sets per week, with a standard error of 4.59. The attention-control mean was 1.9, with a standard error of 0.86. The recalculated unadjusted mean difference is 44.94, with the posted interval from 35.79 to 54.09. The registry’s primary analysis used mixed models, but the model specification and its treatment of missing observations are not reported in the registry record.

7. Results Posted in the Registry

• STAR Intervention: mean 46.84 versus 1.90 on control; difference 44.94 (95% CI 35.79 to 54.09), standardized effect d = 1.43; 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.

Subjective Functional Status at 25 Weeks

• 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 errors.
• Result:
  • STAR Intervention: mean 16.68 versus 18.30 on control; difference -1.62 (95% CI -5.58 to 2.34), standardized effect d = -0.12; z-test p = 0.423.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between STAR Intervention and the control. The interval gives the range of effects that remain compatible with the data.

Quadriceps Strength at 25 Weeks

• 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 errors.
• Result:
  • STAR Intervention: mean 43.21 versus 41.88 on control; difference 1.33 (95% CI -3.47 to 6.13), standardized effect d = 0.08; z-test p = 0.587.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between STAR Intervention and the control. The interval gives the range of effects that remain compatible with the data.

Pain by the Pain Subscale of the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index at 25 Weeks

• 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 errors.
• Result:
  • STAR Intervention: mean 4.25 versus 4.54 on control; difference -0.29 (95% CI -1.36 to 0.78), standardized effect d = -0.08; z-test p = 0.594.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between STAR Intervention and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary outcomes cover several types of measurement, including subjective functional status, quadriceps strength, pain, fatigue, health-related quality of life, and self-efficacy. The record states that 18 secondary outcomes were posted. It gives numerical summaries in the available outcome details for subjective functional status, quadriceps strength, and WOMAC pain. For these measures, the recalculated arm contrasts are modest in relation to their uncertainty, and each posted interval spans zero. The listed estimates point in different directions rather than reproducing the primary endpoint’s pattern.

This contrast with the primary result matters: the record supports a clear difference for diary-reported lower-extremity exercise volume, but the available secondary summaries do not establish a corresponding difference in the listed clinical measures. The primary endpoint measures an exercise behavior, whereas function, strength, and pain are distinct constructs. A result on one measure should not be treated as a substitute for evidence on another.

Numerical results for the other posted secondary outcomes are not reported in the registry record in the information summarized for this analysis. It is therefore not possible to describe the complete pattern across all secondary outcomes or to infer that unreported results were similar to the three with numerical summaries. The registry lists 30 outcome measures and 44 analyses, which underscores that the primary contrast is only one of multiple statistical questions in the record.

Unadjusted secondary results generally carry less weight than a prespecified primary result because multiple testing can increase the chance of apparently notable findings arising by chance. Whether any multiplicity adjustment, testing hierarchy, or selective reporting procedure was used is not reported in the registry record. Secondary findings are best treated as supporting or exploratory evidence unless the planned analysis strategy establishes otherwise; that strategy is not described.

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

• Subjective Functional Status at 25 Weeks
• Quadriceps Strength at 25 Weeks
• Pain by the Pain Subscale of the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index at 25 Weeks
• Pain by the Bodily Pain Subscale of the Short Form-36v2 at 25 Weeks
• Fatigue at 25 Weeks
• Health-Related Quality of Life at 25 Weeks
• Self-Efficacy at 25 Weeks
• Arthritis Self-Efficacy at 25 Weeks

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous and is summarized by a mean in each arm. A mean describes the average value of a measurement across the participants included in that summary. The posted STAR mean is 46.84 repetitions multiplied by sets per week, and the attention-control mean is 1.9. These group summaries offer a direct description of the measured outcome but do not account for every feature that might be included in a statistical model.

What does the mean difference describe?

The recalculated comparison expresses the STAR mean relative to the attention-control mean as a mean difference of 44.94. A positive difference means the reported mean was higher in the STAR arm for this outcome. The interval from 35.79 to 54.09 communicates uncertainty around that recalculated difference. It is an unadjusted re-calculation from the posted summary statistics, not the numerical estimate from the registry’s mixed-model analysis. The registry record does not provide the mixed-model estimate or its interval.

The unit matters for interpretation. The endpoint is repetitions multiplied by sets per week, based on diary-recorded lower-extremity exercise over a 7-day period. The mean difference is therefore in that same outcome scale. It is not a percentage change or a count of participants. No new ratios or percentages are needed to describe the group contrast.

What do the standard errors tell the reader?

The registry reports standard errors of 4.59 for the STAR mean and 0.86 for the attention-control mean. A standard error describes the statistical uncertainty associated with an estimated mean; it is not the same as the range of individual participant values. In general, variability among individual observations and uncertainty in the estimated average are different quantities. The posted record gives standard errors, not standard deviations, for these arm summaries.

The recalculation uses posted arm-level summaries. It is labeled unadjusted because it does not incorporate covariates or other model structure beyond the summarized arm means and associated information. Such a comparison is useful as a transparent descriptive check, but it may not reproduce a model-based analysis that accounts for repeated measurements, covariates, or other design features. Whether the sponsor’s model included specific covariates or repeated observations is not reported in the registry record.

What does a p-value express?

A p-value describes how compatible the observed data are with a specified statistical null model, under the assumptions of the analysis. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of the difference. The recalculated unadjusted p-value for the primary endpoint is <0.001. The sponsor’s mixed-model analysis reports p <.0001. These p-values are reported in their original formats; the tests arise from different procedures and should not be treated as the same calculation.

The registry labels its reported analysis as a superiority analysis and names mixed models as the method. Mixed models are a general class of methods that can represent dependence among observations, such as repeated measurements on the same participant, and can incorporate other model terms. That general description does not establish which features were used in this trial. The specific model formula, covariance structure, adjustment variables, and handling of missing outcomes are not reported in the registry record.

Why can over-dispersion matter?

For count-like or highly variable outcomes, a simple model may not capture the full spread of the observations. General statistical practice treats over-dispersion as a concern when observed variability exceeds what a chosen model expects. It can affect standard errors and therefore the apparent precision of a comparison. The primary endpoint combines diary-reported days and exercise volume, but the registry information does not provide the participant-level distribution or a model assessment for over-dispersion. It is not possible to determine from the registry record whether this issue was assessed or how it was handled.

Similarly, an outcome distribution may be skewed or contain many low values. The arm means alone do not show the distribution’s shape. The registry does not report distributional diagnostics or transformations for the primary endpoint. This does not invalidate the reported summary; it means that assessment of those modeling choices is not possible from the reported information.

How should the recalculated comparison be used?

The recalculated mean difference is an independent, simple comparison of the posted summary statistics. It provides an interpretable contrast in the endpoint’s original units. The recalculation and the sponsor’s analysis both indicate a primary-arm difference, but the sponsor’s mixed-model test is the trial’s reported analysis. Details needed to reproduce that model are not reported in the registry record. The recalculation should therefore be read as a check on the posted summaries, not as a replacement for the model-based result.

There are many reported outcomes and analyses in the record: 30 outcome measures and 44 analyses are listed. Testing multiple outcomes creates opportunities for chance findings, especially when results are interpreted one at a time without an adjustment strategy. The registry does not report whether a multiplicity procedure was planned or used. The primary endpoint’s designation provides a basis for distinguishing it from secondary questions, but the registry record does not describe a full hierarchy or a prespecified testing sequence.

11. Confidence Intervals and Precision

The recalculated primary mean difference is 44.94 repetitions multiplied by sets per week, with the posted interval from 35.79 to 54.09. The interval does not include zero, which is consistent with the difference indicated by the recalculated unadjusted p-value of <0.001. The registry’s mixed-model analysis reports p <.0001, but it does not give a model-based estimate or interval in the record.

A confidence interval is generally interpreted as a range of effect values compatible with the data and the assumptions used to construct it. It conveys more about the estimate’s precision than a p-value alone: the interval displays a range, whereas a p-value gives a measure tied to a null hypothesis. The confidence level for the recalculated interval is not stated in the available registry information, so no confidence level should be attached to it.

The interval is centered around the recalculated difference and indicates uncertainty in the unadjusted contrast. It does not capture all possible uncertainty about the study’s conduct, measurement, or generalizability. For example, the registry does not report the primary model’s specification, the handling of missing diary data, or the analysis population. Those omissions limit evaluation of whether the reported model and the simple recalculation address precisely the same data structure.

The arm standard errors also describe precision of the means, not the spread of individual exercise records. The STAR standard error is 4.59 and the attention-control standard error is 0.86. These values should not be read as ranges containing most participants. Individual-level variability, distributional shape, and diary completeness are not reported in the registry record. The interval supports a reasonably direct statement about the estimated arm contrast, while leaving those other characteristics unknown.

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 design calculation. For these continuous outcomes, the figures are participants per arm, not total participants and not total events. 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 set to the stated fraction of the observed effect. The trial’s own original sample-size assumptions are not reported in the registry record.

The 80% power column describes the number of participants per arm that the planning calculation estimates would be needed to have an 80% chance of detecting the specified effect under the stated assumptions, if that effect and the calculation’s assumptions were correct. The 90% power column describes the corresponding planning target for a 90% chance. These are design-planning concepts, not statements about the probability that the trial’s result is correct or about the chance that the trial succeeded.

Each row changes the effect size used for planning. The row for 100% of the observed effect uses the full observed effect as the target; the rows for 75% and 50% use smaller target effects. Smaller effects are harder to distinguish from random variation, so the planning figures require more participants per arm as the target effect becomes smaller. This relationship is a general feature of statistical planning, not evidence that the smaller effects occurred in the trial.

These calculations use the observed effect as their starting point and are not observed power. They cannot tell the reader whether the trial was adequately powered according to its original protocol, because that protocol’s design assumptions are not reported in the registry record. The curve and accompanying figures should be interpreted as illustrations under the stated assumptions, not as an account of the trial’s enrollment rationale or a forecast of results in a future study.

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 = 44.940; pooled standard deviation σ = 31.500.
2. n = 2 × (1.96 + 0.842)² × 31.500² / 44.940² = 7.7, rounded up to 8 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 <- 44.94                      # observed difference in means
sigma <- 31.5000055555551                     # 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(1280903)
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 = 8 (80% power), 11 (90% power)
 75% of observed effect: n per arm = 14 (80% power), 19 (90% power)
 50% of observed effect: n per arm = 31 (80% power), 42 (90% power)
power.t.test: 8.8 
Simulated power at n = 8 per arm: 0.759 (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. Analyses Reported by the Sponsor

The registry reports the sponsor’s primary analysis as a mixed-model superiority analysis with p <.0001. The recalculated unadjusted comparison from the posted group summaries gives a mean difference of 44.94 and p <0.001. Both approaches indicate a difference on the primary endpoint. The mean difference and interval belong to the unadjusted recalculation; the registry does not report a numerical mixed-model estimate or interval alongside the sponsor’s p-value.

The two analyses are not interchangeable. The recalculation uses the posted arm-level means and standard errors, while the sponsor’s analysis is identified as a mixed model. The registry record does not provide enough model detail to reproduce the sponsor’s test or to determine precisely how its estimate relates to the unadjusted contrast. The differing p-value formats also should not be interpreted as a direct comparison of effect magnitude.

The discrepancy indicator is false. The recalculation is therefore a useful consistency check on the reported arm summaries, while the mixed-model result remains the registry’s reported analysis. The recalculated result should not be presented as if it were the sponsor’s model output. Readers seeking to evaluate the model’s assumptions or reproduce the reported test would need details that are not reported in the registry record.

15. Multiplicity, Missing Data and Analysis Populations

The record lists 30 outcome measures and 44 analyses. Multiple outcomes can be scientifically useful because they address different aspects of a trial, but interpreting many tests independently raises a multiplicity concern. In general, the more questions tested, the more opportunities there are for chance differences to appear statistically notable. This does not mean that any particular result is false; it means that the testing context affects how strongly isolated p-values should be interpreted.

The primary endpoint is identified, which distinguishes the main question from secondary questions. However, the registry does not report a multiplicity adjustment, a formal testing hierarchy, or a sequence in which hypotheses were to be tested. It is also not reported in the registry record whether the primary and secondary analyses were prespecified in a protocol or statistical analysis plan. Without that information, the degree to which the reported testing strategy controlled multiplicity cannot be assessed.

Missing-data procedures are not reported in the registry record. The primary outcome uses an electronic diary, but the record does not explain how incomplete diaries, missed assessments, or participants without week-25 measurements were handled. The posted arm summaries list 91 participants in each arm; those summaries alone do not establish whether all randomized participants contributed to every outcome or how missing observations were treated.

The analysis population is likewise not reported in the registry record. The record does not state whether the sponsor used an intention-to-treat population, a per-protocol population, or another defined set of participants. The mixed-model method is named, but the model specification and assumptions about missing observations are not described. These are important details because different analysis populations and missing-data assumptions can affect both the estimated contrast and its uncertainty.

Other design and analysis details—including allocation concealment, the identity of the masked group, and the model’s covariates—are also not reported. These omissions do not erase the posted result, but they limit independent evaluation of its robustness and of the relationship between the sponsor’s model and the simpler recalculation.

16. Safety Results

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

Other (non-serious) adverse events

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

The registry’s adverse-event summary lists 91 participants at risk in each arm. It records zero serious adverse events affecting participants in the STAR arm and zero in the attention-control arm. It also records zero other adverse events affecting participants in either arm. These are the figures posted in the record; they describe the adverse-event entries recorded for the trial rather than proving that no event of any kind occurred.

The deaths fields are null, and death counts are not reported in the registry record. The record does not provide serious adverse-event terms, so no event types can be described. The absence of listed event terms should not be interpreted as evidence about particular categories of harm. The record also does not give further detail about ascertainment, follow-up completeness, or the definitions used for adverse events.

These figures are a limited summary of safety reporting. They should be read alongside the stated at-risk groups and the registry’s reporting detail, without treating zero recorded events as a guarantee of safety or as a comparison of overall risk. The trial’s posted safety summary does not establish the absence of uncommon or unreported events.

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

The central statistical finding is a difference between the randomized arms on the primary measure of diary-reported lower-extremity exercise at week 25. The STAR arm had a mean of 46.84 repetitions multiplied by sets per week, compared with 1.9 in the attention-control arm. The unadjusted recalculated mean difference is 44.94, with an interval from 35.79 to 54.09. The sponsor’s mixed-model analysis reports p <.0001.

This result describes the endpoint that was measured. It does not by itself demonstrate a difference in blood pressure, pain, physical function, strength, or quality of life. The registry lists these and other outcomes, but the available numerical summaries do not establish a uniform effect across them. The primary finding should therefore remain specific to the exercise-volume measure rather than being broadened into a claim about every outcome named in the study’s purpose.

The trial compared a behavioral activity program with an attention-control program among older adults with knee osteoarthritis and hypertension. Findings from that population and comparison may not necessarily apply to people with different conditions, settings, or interventions. Detailed eligibility criteria and intervention delivery information are not reported in the registry record, further limiting judgments about which groups or implementations are most comparable.

Statistical evidence is not the same as clinical importance. The record gives the outcome scale and estimates, but it does not report a threshold for a clinically meaningful change in exercise volume. The result also does not establish the durability of any difference beyond the reported week-25 assessment. Longer-term outcomes and their analyses are not reported in the registry record.

Finally, interpretation depends on design and analysis details. The record identifies randomization and a mixed-model primary analysis, but does not describe the model specification, missing-data handling, or analysis population. The reported result is informative about the posted comparison, while those omissions prevent a complete assessment of every assumption behind it.

18. Why This Trial Matters Statistically

This trial illustrates why a clinical result should be interpreted at the level of its actual endpoint. The primary measure is not a general index of health; it is a diary-based measure of lower-extremity exercise volume. Reporting the mean difference in the outcome’s own units makes the contrast more interpretable than relying on a p-value alone. The interval also makes uncertainty visible, rather than reducing the finding to a binary label.

The record offers two kinds of statistical information: arm-level summaries that permit a simple unadjusted recalculation, and a sponsor-reported mixed-model test. Their broad inference is aligned for the primary result, but they answer the comparison through different procedures. Keeping those analyses distinct helps avoid presenting a re-calculation as though it were the sponsor’s model or assuming that the model can be reproduced without its specification.

The record also highlights the importance of separating the primary endpoint from multiple secondary questions. A strong result for exercise volume does not automatically imply corresponding results in function, pain, or strength. Multiple endpoints can provide a fuller view, but incomplete secondary reporting and unreported multiplicity procedures limit how confidently a reader can synthesize them.

Finally, the trial shows why statistical reporting details matter beyond the headline result. Information about missing-data handling, analysis populations, masking, model specification, and sample-size planning affects reproducibility and interpretation. These details are not reported in the registry record. The available statistics still permit a clear description of the primary contrast, while making the boundaries of that interpretation explicit.

19. 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 does not provide a detailed protocol or statistical analysis plan. It names a mixed-model analysis for the primary endpoint but does not report the model formula, covariates, repeated-measures structure, or missing-data assumptions. The primary model estimate and its interval are not reported, which limits comparison with the unadjusted recalculation.

The record does not describe the original sample-size justification, the intended analysis population, or how incomplete electronic diaries and missing week-25 outcomes were handled. Arm summaries list 91 participants in each group, but do not explain which participants contributed to each analysis. Allocation concealment and the identity of the masked group are not reported in the registry record.

The primary outcome relies on diary-reported exercise. The record does not report diary completion, validation procedures, or participant-level distributions. Consequently, it is not possible to assess the extent to which the summaries may be affected by incomplete reporting or unusual values. The posted means and standard errors do not describe the full distribution of observations.

Secondary results are incomplete in the information summarized for this analysis. Although the record lists 18 posted secondary outcomes, numerical results are available for only some of them. The record also lists many outcome measures and analyses, while multiplicity procedures are not reported. This constrains assessment of the overall evidence across outcomes.

The registry does not provide a threshold for clinically meaningful change in the primary exercise measure or establish durability beyond week 25. These limitations qualify the scope and precision of interpretation; they do not change the basic description of the posted primary arm summaries.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Staying Active With Arthritis: RCT of Physical Activity for Older Adults With Osteoarthritis and Hypertension — NCT01280903.
• Registry record last updated 2024-09-19; status last verified 2024-09.
• Results first posted 2018-01-31.
• 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.

23. Record Summary

NCT01280903 is a completed randomized, single-masked, parallel-group behavioral trial sponsored by the University of Pittsburgh. It enrolled 182 older adults with knee osteoarthritis and hypertension and compared the STAR Intervention with a Senior Health Information attention-control intervention. The record lists 2012-01 as the study start and 2015-04 as primary completion.

The primary endpoint was lower-extremity exercise volume at week 25, measured by electronic diary and expressed as repetitions multiplied by sets per week. The posted means were 46.84 for STAR and 1.9 for attention control. The recalculated unadjusted mean difference was 44.94, with an interval from 35.79 to 54.09; the sponsor’s mixed-model analysis reports p <.0001.

The record also lists secondary clinical and behavioral outcomes, but numerical results are not reported for all of them in the information. Details on the primary model, missing data, analysis population, multiplicity, and original sample-size assumptions are not reported in the registry record.