A Study of Physical Activity paTTerns and Major Health Events in Older People With Implantable Cardiac Devices: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of Physical Activity paTTerns and Major Health Events in Older People With Implantable Cardiac Devices (NCT03544424), a registered phase not stated study. The primary outcome is Non-elective Hospital Admissions.

2. Clinical Question

3. Trial Design

This is an observational study, not a randomized treatment comparison. Its title focuses on physical activity patterns and major health events in older people with implantable cardiac devices. The listed intervention is “No intervention,” and the listed group is a study cohort. The record does not state an allocation method or describe a like-for-like control group. It therefore does not support interpreting differences between assigned interventions, because no such assignment is reported.

The cohort description identifies people over 60 years of age with a Medtronic CareLink-compatible cardiac implantable electronic device in situ, recruited from Manchester University NHS Foundation Trust in England. The registry record reports enrollment of 183. Its brief summary describes an observational study of physical activity patterns in 150 older adults with cardiac implantable electronic devices. The reason these counts differ is not reported in the registry record, so they should not be treated as interchangeable descriptions of the analyzed population.

The primary outcome looks backward over the 12 months before enrolment. It counts participants with a non-elective hospital admission, defined as an emergency admission to an NHS hospital in England or Wales for any reason. This is not a prospective comparison of admission rates after an assigned intervention. The record lists Frailty as a secondary outcome and two outcome measures overall, but it does not provide the analysis population or describe how the physical activity measures were collected or categorized.

The study started on 2018-10-12, reached primary completion on 2019-07-03, and is marked COMPLETED. These dates describe the registry record; they do not establish the timing of every measurement or the duration of follow-up for each participant. Further details about follow-up, eligibility procedures, device monitoring, or the 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

Analysis population for the primary outcome, as defined in the registry: People over 60 years with compatible implanted cardiac device

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 Non-elective Hospital Admissions, measured over Retrospective: 12 months prior to enrolment (retrospective data spans 12 months prior to enrolment).

The primary endpoint is the number of participants who had a non-elective hospital admission during the 12 months before enrolment. An admission qualifies when it is an emergency admission to an NHS hospital in England or Wales for any reason. The registry description says these data were collected from NHS England. The endpoint is expressed as participants with an event, rather than as the total number of admissions, so it represents whether each participant had at least one qualifying admission during the specified retrospective period.

In general, a binary endpoint reduces each participant's experience to an event status, such as admission or no recorded admission in the defined period. This can make the outcome straightforward to summarize, but it does not preserve information about the number of admissions per participant, their timing, length of stay, or clinical cause. Those details are not part of the endpoint as described.

Hospital admissions are used in this study as a major health-event measure. The definition includes emergency admissions for any reason, so the endpoint is broad rather than restricted to a particular diagnosis. It may describe the burden of recorded acute hospital use in the cohort, but it cannot by itself identify why an admission occurred or establish that physical activity caused or prevented it.

The registry record does not report the number of participants meeting the endpoint, a comparison estimate, or an uncertainty interval. The endpoint definition is available, but its observed result and the analysis used to estimate it are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

In general, a binary outcome records whether each participant did or did not experience a defined event during a specified period. Here, the endpoint is the number of participants with a non-elective hospital admission in the 12 months before enrolment. The event definition is an emergency admission to an NHS hospital in England or Wales for any reason. Counting participants with an event is distinct from counting every admission: repeated admissions by one person do not create additional participants with the endpoint under the stated measure.

What does the endpoint count?

The endpoint is described as a count of participants, with the event status interpreted as a binary outcome. General summaries for this type of measure can report the number with an event and the number assessed, or estimate an event proportion. An estimate is more informative when paired with an uncertainty interval, because the interval conveys how much sampling variability is compatible with the data under the model. The registry record does not report the endpoint count, denominator used for its analysis, estimated proportion, or confidence interval. No such result can be reconstructed from the enrollment number alone.

What can an observational association establish?

In general, an observational study measures exposures and outcomes without assigning participants to interventions. The study is described as observational, and the registry lists no intervention. This means any association between physical activity patterns and admissions would not, by itself, establish that activity caused a difference in admission experience. Participant characteristics, health status, or other factors could be related to both activity and hospital use. The registry record does not report the covariates measured, an adjusted model, or a confounding-control strategy.

For an association to be interpreted in time, readers also need to know when the exposure was measured relative to the outcome. The admission period is retrospective and precedes enrolment. The record does not state the timing or measurement schedule for physical activity in relation to admissions. It is therefore not possible to establish from the record whether activity was measured before, during, or after the relevant admission period.

Why does over-dispersion matter?

General statistical explanation: over-dispersion occurs when the variability in count data is greater than a chosen model expects. It can arise when participants have different underlying event tendencies or when events cluster. For counts of repeated admissions, a model that assumes less variability than the data contain may produce uncertainty estimates that are too narrow. That concern is distinct from the stated binary endpoint, which counts participants with any qualifying admission rather than the total number of admissions. The registry record does not report a count model, an over-dispersion assessment, or a method for repeated admissions.

What do significance levels and planning illustrations mean?

General statistical explanation: a significance level is a threshold used in a testing procedure to control how often that procedure rejects a null hypothesis when the null is true, under its assumptions. The planning assumptions stated for sample-size illustrations include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They describe hypothetical planning calculations based on a fraction of an observed effect; they are not a reported design rationale for this observational cohort. The record does not state that participants were allocated equally between arms, and it does not report the trial's own sample-size justification.

Sample-size calculations are planning illustrations, not observed power. Observed power is not a substitute for examining the estimate and its uncertainty after data collection. In general, a planning calculation depends on assumptions about the effect to detect, the test, and the design. A calculation based on the observed effect is especially different from a prospective justification, since the observed effect is not known at the planning stage. The registry record does not report the numerical planning results or the specific observed effect used in those illustrations.

What analysis was actually used?

The registry record lists zero analyses. It does not report a statistical model, estimation method, test, confidence-interval procedure, or adjustment for measured characteristics. It also does not say whether the primary outcome was analyzed according to a prespecified protocol. These details cannot be inferred from the endpoint definition or the study's completion status. The available information supports a description of the intended outcome, but not a reconstruction of the statistical analysis.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists two outcome measures, with Frailty identified as a secondary outcome and non-elective hospital admissions as the primary outcome. Considering multiple outcomes can raise a multiplicity question: when several hypotheses are tested, the chance of at least one apparently notable result can increase. General approaches include identifying a prespecified primary outcome, adjusting testing procedures, or interpreting secondary findings as exploratory. The record does not report a multiplicity strategy, a hierarchy among analyses, or whether any adjustment was used.

The record lists zero analyses and does not report a numerical result for either outcome. It therefore provides no basis for assessing how many tests were performed, whether outcomes were selected after looking at the data, or whether any multiplicity adjustment would affect an inference. The statistical analysis plan is not reported in the registry record.

Missing-data methods are also not reported in the registry record. It is not stated whether all enrolled participants had usable admission data, how incomplete records were handled, or whether any participants were excluded from an outcome analysis. The enrollment count and the brief-summary count differ, and the record does not explain whether that difference reflects missing data, eligibility, or another reason. No explanation should be assumed.

The analysis population is not reported in the registry record. It is not stated whether the endpoint denominator includes every enrolled participant, only participants with linked hospital data, or another defined subset. Since the endpoint is binary, incomplete event ascertainment could affect both the event count and the denominator. Without the analysis population and missing-data handling, the completeness and representativeness of any outcome estimate cannot be evaluated.

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.

The registry's serious adverse event entry lists a study cohort with 183 participants at risk, 0 participants affected by serious events, 0 affected by other events, and 0 deaths. These are the figures recorded for the cohort. The registry lists no serious adverse event terms.

These entries should be read as registry reporting, not as proof that no adverse events of any kind occurred. The record does not describe the adverse-event collection period, ascertainment procedures, event definitions beyond the reporting categories, or completeness of reporting. It also does not explain whether the figures cover the entire study period or a particular observation window. Those details are not reported in the registry record.

Zero reported serious events does not establish that the study exposure or participants' activity patterns were risk-free. This was an observational study with no listed intervention, and the serious adverse event figures do not provide a randomized safety comparison. They also do not describe the frequency or severity of individual non-serious events. The figures should therefore be treated narrowly as the counts entered in the registry, without extending them to conclusions about safety or causation.

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

The registry record identifies an observational study of physical activity patterns and health events among older people with cardiac implantable electronic devices. It specifies a primary outcome: participants with an emergency, non-elective admission to an NHS hospital in England or Wales for any reason during the 12 months before enrolment. It also lists Frailty as a secondary outcome and marks the study COMPLETED.

The record does not report the primary endpoint result, an association estimate, an uncertainty interval, or an analysis. It therefore does not show how many participants had an admission or whether physical activity patterns were related to admission experience. The enrollment figure of 183 cannot be used to fill in the missing endpoint result. The brief summary instead describes 150 older adults, and the record does not explain that difference.

Even if an association estimate were available, the observational design would not establish that physical activity caused a change in admissions. The primary outcome refers to a retrospective period before enrolment, and the relative timing of activity measurement and admissions is not reported. Important details about confounding adjustment, missing data, and the analysis population are also absent from the registry record.

The serious adverse event entry reports 0 serious events, 0 other events, and 0 deaths among 183 participants at risk. These are registry entries and do not establish the absence of all adverse events or provide a comparative safety assessment. The record does not state the ascertainment period or methods.

In general, a complete statistical interpretation needs an outcome estimate, a clear denominator, and a measure of uncertainty, alongside an understanding of the design and analysis. Those elements are not reported for the primary outcome. The record supports describing the study question and outcome definition, but it does not support a conclusion about the frequency of admissions, the precision of an association, or a causal effect.

13. Why This Trial Matters Statistically

This study illustrates why the endpoint definition and study design must be read together. The primary outcome is a binary participant-level measure of whether a person had a qualifying emergency hospital admission during the 12 months before enrolment. It is not a count of all admissions, and it does not distinguish admission causes. That distinction determines what an eventual estimate could mean.

The observational design also shapes the interpretation. A relationship between physical activity patterns and admissions, if estimated, could be influenced by other participant characteristics. Without reported adjustment methods or a clear account of timing, association would not be equivalent to causation. The retrospective outcome period makes the ordering of activity measurement and admissions especially important, but that timing is not reported in the registry record.

The record also demonstrates the value of transparent outcome reporting. It identifies the endpoint and gives an enrollment figure, but does not report the event count, analysis denominator, estimate, or uncertainty. Without these, readers cannot evaluate the observed frequency or precision. The difference between enrollment of 183 and the brief summary's description of 150 adults adds an unresolved question about the population represented by each figure.

Finally, planning calculations need to be separated from observed evidence. A sample-size illustration based on a fraction of an observed effect is not a trial-specific design justification and does not show observed power. In this case, the record describes an observational cohort rather than equal allocation between two arms. These distinctions matter because a numerical planning exercise cannot replace a reported analysis of the actual cohort.

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 available registry description leaves several trial-specific details unresolved. Enrollment is recorded as 183, but the brief summary describes 150 older adults. The registry record does not explain whether these figures refer to different stages, eligibility sets, or analysis populations. It is therefore unclear which population would be represented by a primary outcome analysis.

The primary endpoint covers non-elective admissions in the 12 months before enrolment, but the timing and method of physical activity measurement are not reported in the registry record. The relation between exposure measurement and the retrospective admission window cannot be established. Because the admission definition includes emergency admissions for any reason, the endpoint is broad and does not identify a particular diagnosis or cause.

The record does not report the number of participants with the primary endpoint, a denominator for analysis, or an estimate with uncertainty. It lists zero analyses. Details about missing outcome data, hospital-record linkage completeness, exclusions, and the analysis population are not reported in the registry record. Thus, neither the completeness of ascertainment nor the handling of incomplete observations can be assessed.

No randomized comparator is listed, and allocation is not stated. The record does not report adjusted analyses or a confounding-control strategy, limiting any causal interpretation of a possible association. It also does not report the statistical analysis plan, a sample-size justification for the study, or a multiplicity strategy for the two outcome measures.

The adverse event entry reports zero serious events, zero other events, and zero deaths among 183 at risk, but the collection period and ascertainment methods are not described. These limitations concern what can be concluded from this registry record; they do not establish that omitted methods or analyses did not occur.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study of Physical Activity paTTerns and Major Health Events in Older People With Implantable Cardiac Devices — NCT03544424.
• Registry record last updated 2025-05-21; status last verified 2025-05.
• Results first posted 2025-05-21.
• 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

NCT03544424 is a completed observational study titled “A Study of Physical Activity paTTerns and Major Health Events in Older People With Implantable Cardiac Devices,” sponsored by the University of Manchester. The record lists enrollment of 183, a start date of 2018-10-12, and primary completion on 2019-07-03. The cohort description concerns people over 60 years with a compatible implanted cardiac device, recruited from Manchester University NHS Foundation Trust in England. The brief summary describes 150 older adults; the difference from the enrollment figure is not explained.

The primary outcome is participants with non-elective hospital admissions during the 12 months before enrolment, defined as emergency admissions to NHS hospitals in England or Wales for any reason. Frailty is listed as a secondary outcome. No intervention or randomized comparator is listed, and the record lists zero analyses. The primary outcome result, analysis population, statistical methods, and missing-data approach are not reported in the registry record. The serious adverse event entry records 0 serious events, 0 other events, and 0 deaths among 183 participants at risk.