Text Messaging to Increase Activity in Midlife: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Text Messaging to Increase Activity in Midlife (NCT04849052), a randomized phase 1 study. The primary outcome is Change in Moderate-Vigorous Physical Activity [MVPA].

2. Clinical Question

This is a question about a measured activity outcome over follow-up, not a direct test of every element of the intervention separately. Because both groups receive physical-activity-related content, the intended comparison concerns the MASTERY program against the attentional control condition, rather than against no intervention. The record identifies the study as a randomized pilot trial. It does not report a specific hypothesis about the size of a difference, a threshold for a meaningful difference, or the statistical procedure used to compare the groups.

3. Trial Design

The registry describes a randomized, parallel-group pilot trial with single masking. The trial is listed as phase 1 and completed. It records an enrollment of 116. The masking field does not identify which participants or study personnel were masked, and the registry record does not report the randomization procedure, allocation concealment, or the allocation ratio actually used.

The intervention, MASTERY, is a behavioral program using interactive text messages. Its described components are positive psychology activities, physical activity goals, and techniques intended to reduce midlife-specific stress. The summary describes weekly two-way sessions over 12 weeks. The attentional control condition is also behavioral. It includes the physical activity component and added educational guidance about physical activity, while omitting positive psychology and midlife-related content. The summary calls this an attention-matched control, but details of how attention was matched are not reported in the registry record.

The primary outcome is change in moderate-vigorous physical activity, assessed using an ActiGraph accelerometer worn for one week at baseline, 6 weeks, and 12 weeks. The record describes analyses of change from baseline at the two follow-up times. It states that 30 participants in the MASTERY group were included in analyses at both time points. In the attentional control group, 32 participants were included at 6 weeks and 36 at 12 weeks.

Those analysis counts describe the stated primary-outcome populations, not necessarily the number randomized to each group. The registry record does not explain why the numbers included differ across groups and time points. It also does not report the timing of randomization, adherence criteria, or whether additional analysis populations were defined. These details limit how fully the trial’s implementation and analysis can be reconstructed from 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.

Before assignment: Though 116 participants were enrolled in the study, only 80 were randomized. 27 participants were found to be too physically active when wearing the accelerometer, 6 withdrew consent, 2 were lost to follow-up, and 1 was terminated prior to randomization.

Baseline

Week 6 assessment

Reasons for not completing this period:

Week 12 assessment

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: MASTERY Intervention: 30 participants were included in analyses at both time points. Attentional control: 32 participants were included in the analysis at 6 weeks, and 36 were included in the analysis at 12 weeks.

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 Change in Moderate-Vigorous Physical Activity [MVPA], measured over Baseline, 6 weeks, 12 weeks.

The primary endpoint is change in moderate-vigorous physical activity (MVPA), measured in minutes per day. Participants were to wear ActiGraph accelerometers for one week at baseline, 6 weeks, and 12 weeks. The stated outcome is change from baseline in the average daily minutes of MVPA at each follow-up time. The registry describes ActiGraph accelerometers as validated measures of physical activity and notes their use in studies involving patients with medical illness.

MVPA is a continuous measure: it records an amount of activity rather than assigning each participant to a simple event category. An average can describe activity across the measurement period, while change from baseline focuses attention on how the measured value shifts over follow-up. In general, objective measurement can reduce reliance on participants’ recall compared with self-report, though it does not remove all measurement limitations. Device wear, data processing, and the definition of valid measurement periods can affect the resulting estimates; those operational details are not reported in the registry record.

The record specifies two follow-up assessments, at 6 weeks and 12 weeks, rather than a single follow-up value. The primary outcome description does not state whether the main comparison is between groups at each time point, a group-by-time contrast, or another summary. Nor does it report endpoint estimates, uncertainty intervals, or tests of the group differences. Therefore, the outcome definition is available, but the magnitude and precision of any observed change are not.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the primary outcome represent?

The endpoint is a continuous measure: average minutes of MVPA per day. In general, a continuous outcome can be summarized by a mean, which describes the center of the observed values, and a standard deviation, which describes how spread out individual values are around that mean. The registry identifies the mean as the summary parameter and the standard deviation as the dispersion measure. It does not report the corresponding values for either group or follow-up time.

The endpoint is expressed as change from baseline. In general, change scores compare a follow-up measurement with a participant’s baseline measurement. A between-group comparison of change asks whether the average shifts differ across randomized groups. This is distinct from comparing follow-up averages alone. The registry record does not specify which exact model or contrast was used to estimate the changes or compare the groups.

How should repeated measurements be understood?

The outcome is assessed at baseline, 6 weeks, and 12 weeks, with changes from baseline described for the two follow-up assessments. In general, repeated measurements from the same participant are related rather than independent. Statistical analyses should account for that relationship when they use multiple observations from each participant. Possible approaches vary, and the chosen approach can affect the estimate and its uncertainty. The statistical model and its assumptions are not reported in the registry record, so no particular repeated-measures method should be attributed to this trial.

Separate estimates at each follow-up can answer time-specific questions, while a model can also describe patterns over time. Those approaches do not necessarily answer the same question. The record identifies the measurement times but does not say whether the analyses treated each follow-up as a separate comparison, jointly modeled the observations, or used another method. It also does not report whether estimates were adjusted for baseline values or other covariates.

What does randomization contribute?

In general, random assignment aims to make groups comparable with respect to both measured and unmeasured characteristics at the start of a trial. This supports interpreting a between-group contrast as an estimate of the effect of assignment to the intervention package, subject to the conduct of the trial, missing outcome data, and analysis choices. Randomization does not guarantee that every feature of the groups will be identical, particularly in a pilot study. The registry identifies the trial as randomized but does not describe its sequence generation or allocation concealment.

The control group receives physical activity content and guidance, while MASTERY includes additional positive psychology and stress-reduction content. Thus, in general, a group contrast would compare these assigned program packages. It would not by itself identify the separate effect of text messaging, physical activity guidance, positive psychology, or stress reduction. Nor does the description establish whether participants followed all assigned components.

What would uncertainty measures add?

In general, a confidence interval describes statistical uncertainty around an estimated effect. Its width reflects the precision of the estimate under the statistical model and assumptions; a narrower interval indicates greater precision than a wider interval. A confidence interval also helps readers judge which effect sizes remain compatible with the observed data. The registry record does not report a confidence interval for the primary outcome.

A p-value, in general, measures how unusual the observed data or more extreme data would be under a specified null hypothesis and model. It does not measure the probability that the null hypothesis is true, the probability that a result occurred by chance, or the importance of an effect. The registry record does not post a primary-outcome p-value or state the testing procedure. Without effect estimates and uncertainty measures, neither the size nor the precision of the primary comparison can be assessed.

Why can variation and over-dispersion matter?

For a continuous outcome, the standard deviation describes observed spread, while the standard error describes uncertainty in an estimated mean or contrast. They are not interchangeable. In general, greater variability can make a group difference less precise, all else being equal. The registry identifies standard deviation as the dispersion measure but does not report observed dispersion values for MVPA.

Over-dispersion is a general concern when a statistical model assumes less variability than the data contain. It is especially relevant for outcomes modeled as counts or rates, where extra variability can make standard errors too small if the model is not adapted. The primary endpoint is described as a continuous mean, not a count endpoint, and the registry record does not report an over-dispersion assessment or a model that would permit such an assessment. No claim about over-dispersion in this trial is warranted.

What do the planning assumptions tell readers?

The registry’s sample-size assumptions describe a planning illustration based on an observed effect: a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. These are assumptions for a planning calculation, not evidence that the trial had that design or used that statistical plan. The record does not report sample-size results for this primary endpoint, and the primary comparison is not reduced to one result because it has multiple time points. Any planning illustration would therefore require caution and must not be read as observed power or as a trial-specific design justification.

In general, a sample-size calculation asks how much information a proposed study would need under specified assumptions. It does not establish the precision achieved in a completed study. Actual precision depends on the observed data, variability, analysis method, and amount of usable outcome information. Since primary-outcome estimates and uncertainty are not reported, the precision achieved in this trial cannot be assessed from the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome is described at 6 weeks and 12 weeks, and the registry also lists secondary outcomes covering text-message session completion, utility ratings, physical activity, and sedentary time. It records 24 outcome measures. When a study examines multiple outcomes or time points, the chance of at least one apparently unusual result can increase if many tests are conducted without accounting for multiplicity. In general, prespecifying a primary comparison and using an appropriate multiplicity strategy can help readers distinguish confirmatory analyses from exploratory ones.

The registry record does not report a statistical analysis plan, the number of comparisons tested, a multiplicity adjustment, or which comparisons were designated as primary within each time point. It lists no analysis records and does not post results for the primary or secondary outcomes. The record therefore does not support an assessment of how multiplicity was handled or whether reported findings were selected from a larger set of analyses.

Analysis populations and missing data also matter. The primary-outcome description says 30 MASTERY participants were included at both follow-up times, while the attentional control group includes 32 at 6 weeks and 36 at 12 weeks. The reasons for these different analysis counts, the amount or pattern of missing outcome data, and any missing-data method are not reported in the registry record. There is no reported imputation procedure, sensitivity analysis, or definition of an intention-to-treat or per-protocol population.

In general, an analysis restricted to participants with observed measurements can be affected if the availability of measurements is related to outcomes or group assignment. Different assumptions about missingness can lead to different estimates. The listed analysis counts alone cannot show whether such bias occurred or how it was addressed. The registry record also does not explain whether participants with no usable accelerometer data were excluded under a prespecified rule. These omissions limit assessment of both the analysis population and the robustness of any estimated group contrast.

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 non-serious adverse event terms

The registry lists zero serious adverse events among 40 participants at risk in the MASTERY group and zero among 40 at risk in the attentional control group. It lists 3 other adverse events among 40 at risk in MASTERY and 5 among 40 at risk in attentional control. Deaths are listed as zero in both groups. The registry does not list serious adverse-event terms.

These entries describe the adverse-event counts recorded for the groups; the record does not provide event descriptions, severity details for the other events, timing, relatedness assessments, or a narrative explaining how events were collected. The other-event counts should not be interpreted as a measure of treatment effect or as a comparison of risk. No percentages or comparative estimates are reported in the registry record, and none can be inferred from the counts alone.

Zero recorded serious adverse events does not establish that no serious events could occur, and it does not establish that the groups have equivalent safety profiles. The listed at-risk counts are not the same as the primary-outcome analysis populations. The registry record does not explain the relationship between those populations or provide additional context for interpreting the safety entries.

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

The registry record establishes that MASTERY was tested in a randomized pilot trial against an attention-matched behavioral control. It identifies a primary outcome based on accelerometer-measured MVPA and describes measurements at baseline, 6 weeks, and 12 weeks. It also identifies the participants included in the primary-outcome analyses at follow-up. These details clarify what the study was designed to examine and how the endpoint was framed.

The record does not report primary-outcome estimates, group averages, changes from baseline, confidence intervals, or p-values. It therefore does not show whether activity measurements increased or decreased in either group, whether the groups differed, or how precisely any difference was estimated. The absence of posted results in the registry record is not evidence that the intervention had no effect; it leaves the effect undetermined from this record.

Even if a group difference were reported, interpretation would depend on its size, uncertainty, analysis assumptions, missing-data handling, and the meaning of the comparison. Since the control condition includes physical-activity content, the contrast would concern MASTERY relative to that active condition, not relative to receiving no program. A group-level result would also not isolate the independent contribution of each MASTERY component.

The study is labeled a pilot trial, but the registry record does not report its sample-size justification or a prespecified threshold for a meaningful outcome difference. Enrollment alone cannot establish whether the primary outcome was measured precisely enough to support a particular conclusion. No medical or behavioral recommendation follows from the information reported in the registry record.

13. Why This Trial Matters Statistically

This trial is statistically informative at the level of its question and measurement structure. It combines randomized assignment with an accelerometer-based continuous endpoint, and it describes activity at baseline and two follow-up times. That setup raises familiar analytic considerations: how to compare change between randomized groups, how to account for repeated observations, and how to describe uncertainty around an effect. The registry record identifies the endpoint and analysis populations, making those questions visible even though it does not report the estimates.

The active comparator is also important to interpretation. Both groups receive physical-activity-related content, while MASTERY includes additional psychological and stress-reduction elements. The intended contrast is therefore between program packages rather than between an intervention and no activity support. This distinction affects what a group estimate could represent and what components it could not identify on its own.

The differing analysis counts across follow-up groups and times illustrate why reporting analysis populations and missing-data methods matters. Counts alone do not explain exclusions or establish bias, but readers need the reasons and methods to assess how the observed data relate to the randomized comparison. Likewise, multiple outcomes and follow-up times make a transparent analysis plan important for understanding which comparisons were intended to be confirmatory.

Because the registry does not post outcome estimates or an analysis plan, this record cannot resolve those statistical questions. Its value for interpretation is chiefly in defining the trial’s design, endpoint, and reporting gaps. That distinction helps prevent study design details from being mistaken for evidence about an intervention’s outcome.

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.

The registry record does not report the primary outcome results, including group-level values, changes from baseline, between-group estimates, confidence intervals, or p-values. This is the central limitation for interpreting the trial statistically: the endpoint is defined, but its observed pattern and precision cannot be assessed.

Information about the analysis is also limited. The record does not report the statistical model, the exact group contrast, covariate adjustment, the analysis plan, multiplicity handling, or a sample-size justification. It does not describe the randomization procedure or identify who was masked. These omissions prevent a detailed appraisal of the analysis choices and trial conduct.

The stated primary-outcome analysis counts differ between groups and follow-up times. The reasons for the differences, the amount and pattern of missing accelerometer data, and the methods used to handle missingness are not reported in the registry record. Device processing details, such as the rules for valid wear and usable data, are also not reported. These details could affect how the continuous activity endpoint is constructed and how representative the analyzed measurements are.

The intervention and control descriptions identify their broad content, but the registry record does not report participant adherence, intervention fidelity, or the extent to which participants received each component. The age range and fuller eligibility criteria are not reported either. As a result, the intended population and the delivery of the programs cannot be characterized beyond the registry description.

Finally, the available adverse-event entries lack event terms and contextual detail. The counts do not establish comparative safety, and the record does not describe event collection or relatedness assessments. These reporting limitations do not demonstrate that the trial lacked further analyses or documentation elsewhere; they limit what can be concluded from the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Text Messaging to Increase Activity in Midlife — NCT04849052.
• Registry record last updated 2026-09-02; status last verified 2026-07.
• Results first posted 2026-09-02.
• 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

NCT04849052 is a completed, randomized, parallel-group phase 1 pilot trial listed under the title “Text Messaging to Increase Activity in Midlife.” It compares MASTERY, a multicomponent interactive text-message intervention, with an attentional control condition. The stated primary outcome is change in average daily minutes of MVPA measured with ActiGraph accelerometers at baseline, 6 weeks, and 12 weeks.

The registry describes 30 MASTERY participants in analyses at both follow-up times, and 32 and 36 attentional control participants in analyses at 6 weeks and 12 weeks, respectively. It also records zero serious adverse events and zero deaths in both groups, with other adverse-event counts of 3 and 5. The primary-outcome estimates and statistical analysis results are not reported in the registry record.