Respiratory Kinematics of Cough in Healthy Older Adults and Parkinson's Disease: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Respiratory Kinematics of Cough in Healthy Older Adults and Parkinson's Disease (NCT02183519), a non-randomized phase 1, phase 2 study. The primary outcome is Peak Expiratory Flow Rate.

2. Clinical Question

3. Trial Design

The registry record describes a completed, parallel, non-randomized study sponsored by the University of Florida. Enrollment is listed as 44. The study is classified as Phase 1 and Phase 2, and the recorded study dates are 2014-10 for the start and 2015-08 for primary completion. These administrative details describe the registered study; they do not establish how many participants contributed data to the primary outcome.

The two groups were healthy older adults and people with Parkinson’s disease. Participants in both groups received voluntary and reflex cough testing. Voluntary cough involved coughing on command; reflex cough was elicited using capsaicin. There was no masking. Because allocation was non-randomized, group membership was not assigned by chance according to the record. The registry cautions that the arms are not a like-for-like control comparison.

This design is suited to describing cough measurements in the groups and procedures recorded, but group differences could reflect features other than Parkinson’s disease. The registry record does not report a randomized allocation process, a masked assessment procedure, or a separate untreated comparison group. It also does not give enough detail to evaluate the timing or order of the cough procedures, the capsaicin administration protocol, or whether all participants completed each measurement.

The registered primary outcome is peak expiratory flow rate, measured in liters of air/second, with a timeframe of 1-2 hours. It is described as a mean with standard deviation. Although the record identifies one outcome measure, it does not provide numerical group results or analysis results. Detailed eligibility criteria, participant characteristics, and the protocol’s rationale for the planned enrollment 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.

Before assignment: 10 PD participants did not respond to 200micro-molar capsaicin, and received the 500 micro-molar single dose. 3/10 PD participants did not respond to 500, and thus did not produce analyzable data. Due to a computer error, data was lost for 3 of the HOA participants. Complete data sets were analyzed for 13 PD and 25 HOA participants.

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 Peak Expiratory Flow Rate, measured over 1-2 hours.

Peak expiratory flow rate is the maximum volume of air expelled per unit time during each cough in a cough epoch. The registry records the unit as liters of air/second and specifies a measurement timeframe of 1-2 hours. It describes the outcome as a mean with standard deviation. In general, a flow measure captures how rapidly air is expelled, and it can be used to characterize cough performance under the different testing conditions.

The study description connects this measure to cough strength and compares voluntary cough, prompted by an instruction to cough, with reflex cough, elicited by capsaicin. The endpoint therefore provides a quantitative way to describe cough-related airflow in the study groups and procedures. It does not by itself describe every aspect of cough, such as the full chest-wall movement, cough sensitivity, or other respiratory function. The registry record does not report how many coughs contributed to each participant’s outcome, how repeated coughs were combined, or whether the analysis accounted for within-participant repetition.

Although the endpoint and its measurement unit are specified, the numerical peak-flow results are not reported in the registry record. There is consequently no posted mean, standard deviation, group contrast, or estimate of precision to interpret. The outcome definition identifies what was intended to be measured, but it is not evidence of the magnitude or direction of a finding.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The record describes a continuous primary outcome reported as a mean with standard deviation. In general, a mean is a way to summarize the central level of measured values, while a standard deviation describes their spread around that mean. They answer different questions: a group mean locates the measurements, and the standard deviation describes variability among them. Neither is reported numerically for peak expiratory flow rate in the registry record, so those summaries cannot be compared or interpreted for this study.

In general, a group contrast estimates how far apart the group summaries are on a chosen scale. A confidence interval expresses uncertainty around an estimated quantity by giving a range of values compatible with the data and the method used. A p-value, when reported, describes how unusual the data would be under a specified null model; it does not measure the size or clinical importance of a difference. The registry record gives no effect estimate, confidence interval, or p-value for the primary outcome. It also lists no analyses. These methods therefore explain how such statistics would usually be read, not what this study found.

The study uses a non-randomized, parallel design. In general, parallel groups are observed as distinct groups, while random allocation is a method for making group assignment independent of participant characteristics on average. Here, the registry identifies the groups by health status and explicitly warns that they are not a like-for-like control comparison. A statistical comparison could describe a difference between the groups, but the non-randomized design alone would not make that difference a causal effect. The record does not report an adjustment strategy or a model intended to address possible differences between groups.

The outcome is defined for each cough in a cough epoch, and both voluntary and reflex cough testing are described. Repeated measurements from one participant are generally related rather than independent. In general, an analysis of repeated measures may need to account for that dependence; treating every cough as independent can make uncertainty appear smaller than it is. The registry record does not report the number of coughs per participant, the way repeated coughs were summarized, or whether a repeated-measures method was used. The endpoint is described as a mean with standard deviation, but no further analysis details are available.

What does the reported summary measure mean?

For a continuous outcome, the mean and standard deviation provide a compact description of a distribution. The mean can be affected by unusually high or low observations, and the standard deviation is most informative when the distribution’s shape is reasonably understood. In general, a skewed distribution or influential extreme values may make a mean and standard deviation less representative of a typical participant. The registry record does not report distributions, individual values, or graphical summaries for peak expiratory flow rate, so the shape and presence of influential observations cannot be assessed.

Why can over-dispersion matter?

In general, over-dispersion means that observed variability is greater than a model assumes. When a model understates variability, its standard errors can be too small and its confidence intervals too narrow, making evidence appear more precise than warranted. This issue is relevant to some count and repeated-measure analyses, depending on the data and model. The primary outcome is a continuous flow measure, and the record does not report a model or variance assessment. There is no basis in the registry record to determine whether over-dispersion was relevant or how it was handled.

What do the planning assumptions establish?

The registry includes a description of a sample-size planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It says that the planning effect is a stated fraction of the observed effect and that non-time-to-event illustrations are expressed as participants per arm for 80% power or another stated power level. These are descriptions of planning assumptions, not results from the trial and not observed power. The record does not include the observed effect or numerical planning estimates in the information available for interpretation. It does not report the trial’s own sample-size justification. The planning description therefore cannot be used to infer enrollment adequacy, the probability of detecting an effect, or the precision of the study’s findings.

More generally, power is a design-stage quantity tied to assumptions about an effect, variability, allocation, and analysis. A post hoc calculation based on an observed effect does not tell readers the probability that the trial’s result is true. If planning estimates are shown elsewhere alongside registry outcomes, they should be read as illustrations under stated assumptions, not as observed findings. Here, the primary numerical outcome and observed effect are not reported in the registry record, leaving no study-specific effect estimate to interpret.

What is missing for an inferential reading?

An inferential interpretation would need the outcome summaries and an explicit account of the analysis: the analyzed population, handling of repeated cough measurements, group comparison, model assumptions, missing-data handling, and uncertainty estimates. The registry record does not report these details. It also does not describe interim analyses or a prespecified statistical plan. Their absence from the record does not establish that no such procedures existed; it means they are not reported in the registry record. Without these elements, no claim about statistical significance, precision, or robustness can be made from the posted results.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Healthy Older Adults", "Parkinson's Disease")
n   <- c(25, 13)
m   <- c(4.34, 3.92)
sp  <- c(0.202, 0.274)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Healthy Older Adults  25  4.340  0.202  4.257  4.423
CARM  Parkinson's Disease  13  3.920  0.274  3.754  4.086

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome measure: peak expiratory flow rate. That does not by itself establish how many statistical comparisons were planned. The study description includes two participant groups and both voluntary and reflex cough testing, which could motivate more than one descriptive contrast, but the record lists no analyses and does not report an analysis plan. The number of inferential tests, any hierarchy among them, and any adjustment for multiple comparisons are not reported in the registry record.

In general, multiplicity refers to the consequences of drawing conclusions from multiple statistical tests or outcomes. When many tests are considered, the chance of at least one apparently notable result can increase unless the analysis plan accounts for that multiplicity. Whether this concern applies, and how it should be handled, depends on the prespecified questions and analysis strategy. Those details are not reported, so no judgment about multiplicity control is possible.

The record does not report analyzed sample sizes for the primary endpoint, missing outcome values, exclusions, or the method used to handle missing data. It therefore cannot establish whether all enrolled participants contributed measurements or whether the available measurements represent the enrolled groups. The safety denominators are not a substitute for outcome analysis counts. The analysis population, including whether it was defined by enrollment, completion, or availability of a measurement, is not reported in the registry record.

In general, missing data can affect both the amount of information available and the interpretation of a comparison, particularly when missingness relates to participant characteristics or outcomes. Without counts, reasons, and a stated method, readers cannot assess the likely direction or size of such effects. The registry record also does not report interim analyses or a detailed statistical analysis plan. These omissions limit assessment of whether the reported analyses, if any, followed planned procedures; no analyses are listed in the record.

12. 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 safety record lists 25 healthy older adults at risk and 13 people with Parkinson’s disease at risk. In each group, the serious adverse event count is 0, the other adverse event count is 0, and deaths are 0. No serious adverse event terms are listed. These are the counts entered in the registry record for the stated groups.

A zero count means no events of that category are recorded among the listed participants at risk. In general, a zero observed count is not proof that an event is impossible or that no event occurred outside the scope of the recorded collection and reporting. Its interpretation depends on how safety events were collected, the observation period, and the completeness of reporting. The registry record does not provide enough detail to assess those features.

The safety figures do not describe cough-flow outcomes, the number of participants with usable endpoint data, or a comparison of the effectiveness of any intervention. They also do not establish that the groups had equivalent safety experience. The capsaicin and cough-testing procedures are described, but the record does not give further detail about how adverse events were solicited or classified. Accordingly, the figures should be read narrowly as the recorded event counts and denominators, rather than as a complete characterization of risk.

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

The registry record establishes the study’s question and measurement framework: it describes voluntary and capsaicin-elicited reflex cough testing in healthy older adults and people with Parkinson’s disease, and identifies peak expiratory flow rate as the primary outcome. It also gives the endpoint unit and measurement timeframe. These registry entries show what the study set out to examine, not what its measurements demonstrated.

The record does not report numerical peak-flow results, group summaries, effect estimates, uncertainty intervals, p-values, or analysis results. Consequently, it does not support a statement about whether one group had higher or lower flow, whether voluntary and reflex cough differed, or how precisely any contrast was estimated. Any numerical or directional conclusion about those outcomes would require results that are not reported in the registry record.

The non-randomized design also limits what a group comparison could mean. In general, a measured association between group membership and a cough outcome is not necessarily caused by the group-defining condition. The registry itself cautions that the arms are not a like-for-like control comparison. Because there are no posted primary-outcome results or reported adjustment methods, neither the size of a possible association nor its sensitivity to group differences can be assessed.

The safety record reports zero serious adverse events, zero other adverse events, and zero deaths for the listed at-risk groups. Those entries should not be interpreted as evidence about the primary endpoint or as proof that the procedures are risk-free. They are limited registry counts whose collection details are not reported.

The study may be useful as a record of a research question and testing approach, but the information recorded is insufficient to assess the observed cough measurements. No conclusion about clinical benefit, treatment effect, or the presence or absence of a meaningful group difference follows from the endpoint definition alone. The registry record supports a description of the design and registered outcome; it does not support an outcome-based conclusion.

14. Why This Trial Matters Statistically

This study is statistically interesting because its question combines two kinds of cough testing with groups defined by health status. The voluntary test uses a command, while the reflex test uses capsaicin. Peak expiratory flow rate supplies a continuous measure of airflow during a cough. In general, a continuous measure can capture gradations in performance that a simple event count would not, but its interpretation depends on the measurement protocol, variability, and analysis strategy.

The non-randomized structure is central to interpreting a group comparison. Comparing people with Parkinson’s disease with healthy older adults can describe patterns in the measured groups, but it does not have the protections of random assignment against differences between groups. The registry explicitly cautions that the arms are not a like-for-like control comparison. This is an important distinction between descriptive association and causal inference, especially when an outcome might be influenced by characteristics beyond the group label.

The measurement framework also raises general analytic questions. The outcome is defined at the level of each cough in a cough epoch, and participants undergo both voluntary and reflex testing. Repeated measurements within a participant may be correlated. Appropriate summaries or models need to reflect the data structure if repeated coughs are included. The record does not report how cough-level readings were summarized or analyzed, so readers cannot evaluate this issue for the study’s results.

Finally, the record illustrates why outcome registration and outcome reporting are different. It names a primary measure and its unit, but does not report the numerical results or analyses. Without those results, neither effect size nor precision can be evaluated. The design and endpoint make the intended question intelligible, while the missing outcome data prevent a statistical answer to that question from the registry record.

15. 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 main trial-specific limitation for interpretation is the absence of numerical primary-outcome results. The registry names peak expiratory flow rate and describes its measurement, but supplies no group means, standard deviations, contrast estimates, or inferential statistics. No analyses are listed. As a result, the registered primary question cannot be answered from the record’s outcome entries.

The study is non-randomized, and the record explicitly cautions that the arms are not a like-for-like control comparison. That limits causal interpretation of any group difference, even if numerical results were available. The record does not report participant characteristics that would help readers understand the comparability of the groups, nor does it describe statistical adjustment for potential differences.

Important measurement details are also absent. The registry does not report the number of coughs recorded per participant, the aggregation of cough-level values, the order or timing of voluntary and reflex testing, or how the capsaicin procedure was administered beyond its use to elicit reflex cough. It does not describe endpoint data completeness or the handling of repeated measurements.

The registry record does not report detailed eligibility criteria, the analysis population, missing-data counts or methods, or the statistical analysis plan. It also does not give a sample-size justification or numerical planning illustration in the information available for interpretation. These gaps constrain assessment of representativeness, precision, analytic choices, and robustness. The absence of these details from the record should be understood as a reporting limitation, not evidence that the procedures were necessarily absent from the underlying study.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Respiratory Kinematics of Cough in Healthy Older Adults and Parkinson's Disease — NCT02183519.
• Registry record last updated 2017-03-24; status last verified 2017-02.
• Results first posted 2017-03-24.
• 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.

19. Record Summary

The registry record describes a completed, non-randomized, parallel study sponsored by the University of Florida, with 44 participants enrolled. It is classified as Phase 1 and Phase 2. The groups are healthy older adults and people with Parkinson’s disease, and both groups underwent voluntary cough testing and reflex cough testing using capsaicin.

Peak expiratory flow rate is the registered primary outcome, measured in liters of air/second over a timeframe of 1-2 hours and described as a mean with standard deviation. The stated study purpose concerns cough function and chest-wall and lung movement during voluntary and reflex cough. The registry warns that the groups are not a like-for-like control comparison.

Numerical primary-outcome results and analyses are not reported in the registry record. The safety entries list zero serious adverse events, zero other adverse events, and zero deaths in both groups. Detailed eligibility criteria, analysis populations, missing-data handling, and the statistical analysis plan are not reported in the registry record.