Fit and Strong! Plus Comparative Effectiveness Trial: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Fit and Strong! Plus Comparative Effectiveness Trial (NCT03180008), a randomized na study. The primary outcome is Dietary Intake.

2. Clinical Question

3. Trial Design

This is a randomized, parallel-group comparative effectiveness trial of customary Fit and Strong! and Fit and Strong! Plus. The interventions are behavioral programs, and the registry record identifies the allocation as randomized. Masking is listed as none. Enrollment is 413. The sponsor is the University of Illinois Chicago, and the trial status is completed. The record lists a start date of 2012-12 and a primary completion date of 2018-01-31.

The two arms share a group exercise and self-management foundation. The customary program includes 90-minute classes, with 60 minutes of physical activity and 30 minutes of health education. The described activity includes stretching and flexibility, low-impact aerobics, and lower-extremity strength training. Fit and Strong! Plus retains the core physical activity and osteoarthritis components while adding weight- and diet-related topics to the health education curriculum. The registry record does not give enough detail to characterize every component of the customary education curriculum.

The design is intended to compare the enhanced curriculum with the customary one, so the contrast concerns the addition of weight- and diet-related content within an established program. The record lists secondary outcomes covering physical activity engagement, lower-extremity pain, stiffness and physical function, muscle strength, and physical endurance. The phase is listed as not applicable. Further information about eligibility criteria, allocation procedures, adherence, or implementation fidelity is 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

Analysis population for the primary outcome, as defined in the registry: The number analyzed at each time point varies due to loss to follow-up.

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 Dietary Intake, measured over 2, 6, 12, and 18 months.

The primary endpoint is dietary intake measured as a score on the Healthy Eating Index 2010 (HEI-2010). This index assesses diet quality in relation to the Dietary Guidelines for Americans. Scores range from 0 to 100 points, with higher scores indicating superior diet quality. The record describes the outcome as a mean, with standard error as its dispersion measure, and specifies assessment at 2, 6, 12, and 18 months.

A diet-quality score offers a way to summarize dietary behaviors in a single continuous measure. Repeated assessments can describe how the measure changes over follow-up, while comparisons between randomized groups can address whether the intervention groups differ at particular times or across time. Those are general uses of this kind of endpoint; the registry record does not report the statistical analysis used for these comparisons.

The primary outcome is distinct from the weight-loss hypothesis described in the trial summary. Although the summary anticipates weight loss as an accompanying outcome, the listed primary outcome is HEI-2010 dietary intake. The registry record does not report the observed means, standard errors, group contrasts, or confidence intervals for the HEI-2010 outcome at any of the specified time points.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The record describes a randomized, parallel-group design. Randomization is used, in general, to reduce systematic differences between groups at assignment, making the assigned program the intended basis for comparison. It does not ensure that the groups will be identical in every characteristic, and it does not remove the need to report how participants were analyzed. The registry record does not describe the randomization procedure or the analysis population.

What does a mean and standard error convey?

The primary endpoint is continuous and is summarized as a mean with a standard error. A mean describes the central level of the measured score in a group. A standard error describes the precision of an estimated mean, rather than the spread of individual participants’ scores. In general, a smaller standard error indicates a more precise estimate, while a larger one indicates more uncertainty. Standard errors are not substitutes for standard deviations when the aim is to describe participant-to-participant variability.

For a comparison between groups, the estimated difference in means is usually more directly informative than either group mean considered alone. A confidence interval around that difference communicates a range of effect sizes reasonably compatible with the data and the statistical model. A narrow interval indicates greater precision than a wide interval. These are general principles; no group means, standard errors, between-group estimates, or confidence intervals for the primary endpoint are reported in the registry record.

How should repeated follow-up measurements be considered?

The HEI-2010 outcome is scheduled at 2, 6, 12, and 18 months. Repeated observations from the same participant are generally correlated: a person’s score at one visit may be related to that person’s score at another. Statistical methods for longitudinal data account for this within-person relationship when estimating changes over time or comparing groups across follow-up. Treating all observations as independent when they are not can lead to inappropriate uncertainty estimates.

There are several possible approaches to repeated measurements, including models that estimate group-by-time patterns or methods that compare groups at individual follow-up times. The choice depends on the analysis objective, data structure, assumptions, and missingness. The registry record does not report which approach was used, whether a baseline measurement was included in an adjusted model, or whether estimates were adjusted for other variables.

Why does missing follow-up data matter?

The record notes that the number analyzed at each time point varies because of loss to follow-up. In general, an analysis using only participants with observed follow-up data can be affected if those with missing measurements differ systematically from those observed. Methods for handling missing data rely on assumptions, and those assumptions should be described alongside the analysis. The record does not report the number analyzed at each time point, the reasons for missing measurements, or the method used to address missing data.

Interpretation also depends on the target analysis population. An analysis based on randomized assignment addresses a different question from an analysis restricted to participants who attended or completed the program. The registry record does not specify whether results were analyzed according to assigned group, among program completers, or using another population definition.

What can be inferred from the planning assumptions?

The sample-size assumptions describe a planning illustration using a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. The illustration is described as detecting a stated fraction of the observed effect. Such calculations explore how a hypothetical future study might be planned under assumptions; they are not observed power and do not establish what this trial found. The registry record does not report its own sample-size justification or provide the outcome estimates needed to evaluate an effect-based planning calculation.

In general, a two-sided test considers departures in either direction from the null hypothesis. A significance level is a threshold used in a testing procedure, not a measure of the probability that a hypothesis is true. A normal approximation is a mathematical simplification that may be reasonable under some conditions; its adequacy depends on the outcome and data. The registry record does not report which inferential tests or modeling assumptions were used for the trial analyses.

How should multiple outcomes be handled?

The record lists a primary outcome measured at multiple follow-up times and a set of secondary outcomes. When several outcomes or comparisons are tested, the chance of at least one apparently noteworthy result can increase. Statistical approaches to multiplicity can control or otherwise address this issue, but the appropriate strategy depends on which comparisons are confirmatory and how they are prioritized. No multiplicity approach is reported in the registry record. The number of outcome measures is listed as 8, but the record does not provide analysis results for them.

Over-dispersion is a general concern for count data when observed variability exceeds what a chosen probability model assumes; it can make uncertainty estimates too small if ignored. It is not a reported feature of the continuous HEI-2010 endpoint, and the registry record does not identify a count model for the safety outcomes. No statistical model for those outcomes is reported.

10. Multiplicity, Missing Data and Analysis Populations

The primary endpoint is assessed at 2, 6, 12, and 18 months, and the record also lists secondary outcomes for physical activity engagement, lower-extremity pain, stiffness and physical function, muscle strength, and physical endurance. Multiple outcomes and time points create a multiplicity issue: the more comparisons examined, the greater the possibility of an apparently notable result arising by chance. A prespecified hierarchy, adjustment procedure, or clear distinction between confirmatory and exploratory analyses can help readers interpret such results. None is reported in the registry record.

The record lists 8 outcome measures but no analysis results. It does not report a statistical analysis plan, the number of comparisons actually conducted, whether any adjustment was used, or how outcomes beyond the primary measure were prioritized. The absence of reported multiplicity methods does not show that no method was used; it means the registry record does not document one.

For missing data, the record states that the number analyzed varies by time point due to loss to follow-up. It does not report time-specific analysis counts, missingness patterns, reasons for loss to follow-up, imputation procedures, sensitivity analyses, or assumptions about missing outcomes. Those details are important because complete-case results can be biased if outcome availability is related to participants’ characteristics or unobserved scores.

The analysis population is also not specified. The record does not say whether analyses followed randomized assignment, included only participants who received or completed a program, or used another definition. It likewise does not describe whether all randomized participants were included in the primary analysis. These omissions limit assessment of attrition, selection, and the interpretation of any eventual group comparison.

11. 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 serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: fall (0.5%).

The registry record reports serious adverse events among 1 participant at risk in the Fit and Strong! group and 0 participants at risk in the Fit and Strong! Plus group. For other adverse events, it reports 1 among 210 at risk in Fit and Strong! and 4 among 203 at risk in Fit and Strong! Plus. Deaths are reported as 3 and 4, respectively. These are separate registry entries; the record does not explain whether or how the categories overlap, or give details about the timing or causes of deaths.

The top serious adverse event term is Fall, listed at 0.5%. The registry record does not specify the denominator for that percentage or assign that term to an arm in the information reported. Counts alone do not describe event severity beyond the listed serious-event classification, duration, recurrence, or possible relation to an intervention. Nor do they establish a causal difference between groups. These safety figures should be read as registry-reported counts and not as a complete explanation of the overall safety profile.

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

The trial addresses a focused comparative question: whether adding weight- and diet-related education to Fit and Strong! is associated with different outcomes than the customary program. Random assignment and a parallel-group design provide a framework for comparing the assigned program versions. The primary measure, HEI-2010, reflects diet quality on a scale where higher scores indicate superior diet quality. Those design features clarify what the trial aimed to study; they do not reveal the observed effect.

The registry record does not report primary outcome estimates, tests, or confidence intervals. It therefore does not establish whether diet-quality scores differed between groups, how large any difference was, or how precisely it was estimated. The hypothesis about improved diet behaviors and a significant 5% weight loss is not itself evidence that those outcomes occurred. No conclusion about the success or failure of either program can be drawn from the available outcome reporting.

Even when results are available, statistical significance and practical importance are different considerations. A small effect can be estimated precisely, while a larger effect may remain uncertain if data are limited or variable. Confidence intervals help distinguish these situations by showing the range of effect sizes compatible with the analysis. The registry record does not include such estimates for the primary endpoint, so neither precision nor practical importance can be assessed.

The record does document that enrollment was 413 and that the number analyzed varied over time because of loss to follow-up. Without analysis counts and details of how missing data were handled, it is not possible to judge whether follow-up patterns altered the comparison. Likewise, the listed safety counts are not a substitute for effectiveness results and do not by themselves establish causation or comparative safety.

The appropriate interpretation is therefore limited to the trial’s design, intended outcomes, and recorded safety counts. Results for the primary and secondary outcomes, the analysis methods, and the handling of missing data are not reported in the registry record. Any stronger conclusion would require information not contained in that record.

13. Why This Trial Matters Statistically

This trial is statistically interesting because it compares two related behavioral programs rather than a program with no intervention. The contrast is targeted: Fit and Strong! Plus retains the core physical activity and osteoarthritis components while adding weight- and diet-related topics to health education. This kind of design focuses the research question on the incremental contribution of those curriculum additions, although the results would still need to be interpreted in light of program delivery, participant engagement, and follow-up.

The primary endpoint is a continuous measure of diet quality collected at multiple follow-up times. That structure raises common statistical questions about how to compare groups, account for repeated observations, convey uncertainty, and handle missing measurements. The registry record notes varying numbers analyzed due to loss to follow-up, making transparent reporting of time-specific data and missing-data methods especially important for interpreting any longitudinal comparison.

The trial also lists several secondary outcomes. Considering multiple endpoints and time points calls for a clear analysis hierarchy and transparent reporting of multiplicity methods. Without those details or any outcome estimates, readers cannot distinguish confirmatory findings from exploratory patterns or assess the precision of the comparisons.

The record’s information is thus useful for identifying the intended design and the questions the trial was built to address, but incomplete for judging comparative effects. Its main statistical lesson is that a randomized design and a clearly defined endpoint are necessary foundations, not substitutes for reporting estimates, uncertainty, analysis populations, and missing-data procedures. Those elements are not reported in the registry record.

14. Limitations

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

Several limitations of interpretation arise from the registry record. It does not report observed results for the primary HEI-2010 outcome or the secondary outcomes, so comparative effects and their precision cannot be evaluated. No confidence intervals or statistical tests are reported. The stated hypothesis should therefore not be treated as a result.

The record says that the number analyzed varies at each time point because of loss to follow-up, but it gives no time-specific analysis counts or description of missing-data methods. It also does not report the analysis population, such as whether participants were analyzed according to randomized assignment or under another rule. These omissions prevent a close assessment of attrition and its potential effect on estimates.

Although the design is described as randomized and parallel, details of the randomization procedure and intervention adherence are not reported in the registry record. Masking is listed as none. The record does not describe whether outcomes were measured by blinded assessors, how program delivery varied, or whether participants attended the intended activities. These details could help readers assess implementation and measurement.

The record lists multiple outcomes and follow-up times but does not describe the statistical analysis plan, model specification, handling of repeated measurements, or multiplicity strategy. It also does not report the trial’s own sample-size justification. The safety entries lack explanations of event overlap, event timing, and the denominator for the listed serious-event percentage. These are limitations of what can be concluded from the registry record, not proof that the trial did not collect or analyze the information.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Fit and Strong! Plus Comparative Effectiveness Trial — NCT03180008.
• Registry record last updated 2024-04-19; status last verified 2024-04.
• Results first posted 2024-04-03.
• 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.

18. Record Summary

NCT03180008 is the completed Fit and Strong! Plus Comparative Effectiveness Trial, sponsored by the University of Illinois Chicago. The registry record describes a randomized, parallel-group comparison of customary Fit and Strong! with Fit and Strong! Plus, with no masking and enrollment of 413. The listed primary outcome is mean HEI-2010 dietary intake score, assessed at 2, 6, 12, and 18 months; higher scores indicate superior diet quality.

Secondary outcomes include physical activity engagement, lower-extremity pain, stiffness and physical function, muscle strength, and physical endurance. The record notes that the number analyzed varies by time point because of loss to follow-up. It lists adverse-event counts but does not report effectiveness analyses, analysis methods, or missing-data procedures. Accordingly, the registry record describes the trial question and design, but does not provide the outcome results needed to assess the primary comparison.