Body Weight, Sleep, and Heart Health: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Body Weight, Sleep, and Heart Health (NCT03388788), a registered phase not stated study. The primary outcome is Blood Pressure (BP).

2. Clinical Question

3. Trial Design

The study, NCT03388788, is titled “Body Weight, Sleep, and Heart Health,” with the official title “Circadian Mechanisms of Cardiovascular Risk in Obesity.” Oregon Health and Science University is listed as sponsor. The registry lists a start date of 2018-05-01, a primary completion date of 2024-09-30, and a status of COMPLETED. Enrollment was 17.

The stated aim was to examine circadian mechanisms related to cardiovascular risk, including resting risk markers and how their rhythms respond to standardized stressors. The study also sought to compare lean and obese individuals across the circadian cycle. An exploratory aim concerned pre- and post-synaptic function in the cardiac left ventricle. These are study aims, not reported findings.

Participants completed a 5-day circadian protocol with repeated cardiovascular measurements. The blood pressure description says measurements were collected up to 7 times per participant across the circadian cycle under constant conditions. Resting and exercise readings were obtained at the beginning of wake periods. The exercise condition involved a level described as equivalent to brisk walking. Salivary melatonin was used to identify dim light melatonin onset, or DLMO, and measurements were assigned a circadian phase relative to that marker and grouped into 4-hour intervals.

The record identifies Normal Weight and Overweight arms, but does not state allocation. It explicitly characterizes the study as observational and cautions that enrollment was insufficient and group distribution imbalanced for full statistical interpretation. The registered intervention is positron emission tomography scanning of cardiac function at 3 circadian time points. The registry record does not report further details of the analysis protocol, recruitment flow, or participant-level analysis populations.

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:

Analysis population for the primary outcome, as defined in the registry: These data were collected from an oscillometric blood pressure 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 Blood Pressure (BP), measured over 5 Days.

The primary endpoint is blood pressure measured in mmHg. The registry describes the outcome parameter as a mean, with standard error as the dispersion measure and a timeframe of 5 Days. Readings came from an oscillometric blood pressure device. Both resting blood pressure and exercise blood pressure were collected: the resting measurement was taken in a supine position, while the exercise measurement was taken during cycling at an intensity described as equivalent to brisk walking.

The repeated measurements were intended to characterize blood pressure in relation to three factors specified in the outcome description: weight group, exercise condition, and circadian phase. Circadian phase was anchored to DLMO, calculated using salivary melatonin, and observations were assigned to 4-hour bins. In general, repeated measurements across a circadian cycle can describe patterns that a single measurement would miss, while measuring resting and exercise responses can characterize different physiological conditions. These general purposes do not establish that any particular pattern was found in this study.

The registry record does not report the blood pressure means, standard errors, estimated contrasts, or confidence intervals. It therefore does not give a numerical estimate of the size or precision of any relationship between blood pressure and group, condition, or phase.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry defines the primary outcome as a mean continuous measure of blood pressure in mmHg, with standard error as the dispersion measure. A mean describes the average of measured values. A standard error describes the uncertainty in an estimated mean under a statistical model; it is not the same as the spread of individual participant readings. In general, standard errors become smaller when an estimate is supported by more independent information, but repeated readings from the same participant are not necessarily independent. The registry record does not report the actual means or standard errors.

What does a repeated-measures design mean?

Blood pressure was measured repeatedly across the circadian cycle, up to 7 times per participant, over 5 days. The protocol included resting readings and readings during exercise, and classified observations by circadian phase relative to DLMO. In general, repeated-measures data allow a study to examine within-participant changes as well as differences between participants. However, the statistical analysis must reflect that readings from one participant may be more alike than readings from different participants. Treating every repeated reading as fully independent can make uncertainty appear smaller than it is. The registry record does not state the model used to handle within-participant correlation, so its approach cannot be assessed from this record.

How are the circadian measurements organized?

The description says salivary melatonin was used to calculate DLMO, a circadian phase marker. Each observation was assigned a phase relative to DLMO and binned into 4-hour, or 60-degree, intervals. In general, binning continuous time or phase makes results easier to describe by intervals, but it also groups together observations that may not have identical phase values. The record identifies the binning approach but does not report alternative phase models or sensitivity analyses.

The outcome description identifies weight group as normal or overweight, exercise condition as seated or exercising on the bike, and circadian phase as the center of the circadian bin. This identifies the factors considered in the statistical description, but not the exact contrasts, model terms, or adjustment variables. Those details are not reported in the registry record. No conclusion about the form of the analysis should be inferred from the list of factors alone.

What can a confidence interval tell a reader?

In general, a confidence interval expresses uncertainty around an estimated quantity under the assumptions of the analysis. A narrower interval indicates greater precision than a wider interval for the same type of estimate, but an interval does not correct for bias from an unsuitable comparison or an incorrect model. No confidence intervals for the primary outcome are reported in the registry record. The record also gives no numerical estimate that could be interpreted for size or direction.

Why does the group imbalance matter?

The registry explicitly notes insufficient enrollment and an imbalanced group distribution. In general, unequal group sizes can leave estimates for the smaller group less precise and can complicate comparisons, particularly when the total sample is limited. Repeated readings can add information about within-person patterns, but they do not turn each observation into a separate participant. The enrolled total was 17, but the registry does not report the number with usable primary outcome data in each group, so group-specific precision cannot be described.

The registry includes a sample-size planning illustration based on an observed effect, with assumptions of a two-sided significance level of 0.05, equal allocation, and a normal approximation. Such planning values are illustrations under stated assumptions; they are not observed power and do not demonstrate that the study had adequate power. The planning illustration does not replace a prospective design rationale. The trial's own sample-size justification is not reported in the registry record, and the posted information does not state that the illustration was the design basis for enrollment.

What is not specified about the analysis?

The record identifies 9 outcome measures and 4 analyses but does not provide a complete statistical analysis plan. The model specification, handling of missing readings, treatment of outliers, covariance structure, adjustment for covariates, and rules for selecting analyses are not reported in the registry record. Interim analyses are not reported in the registry record. This means the methods description is not enough to reproduce the analysis or fully assess whether uncertainty estimates reflect the repeated structure and the set of outcomes.

In general, over-dispersion occurs when observed variability is greater than a model assumes. If present, it can make model-based standard errors too small unless the analysis accounts for it. The registry record does not report whether over-dispersion was assessed or whether it is relevant to the blood pressure analysis. Likewise, there is no reported information about distributional checks or model diagnostics. These are general statistical considerations, not claims that a particular issue occurred in this study.

For these reasons, the most defensible reading is limited to the registered measurement scheme, the study's observational nature, and the stated caution about enrollment and imbalance. Numerical primary results and sufficient analysis detail to evaluate their precision are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry identifies 9 outcome measures and 4 analyses. The listed secondary outcomes include coronary microvascular blood flux, flow mediated dilation, heart rate, epinephrine, norepinephrine, and cortisol. The record does not explain which analyses correspond to which outcomes, how many comparisons were made, or which outcomes or contrasts were designated in advance beyond identifying blood pressure as primary. A multiplicity strategy, including whether any adjustment was applied, is not reported in the registry record.

In general, when many outcomes or comparisons are examined, the chance of at least one apparently unusual result can increase. Methods that control multiplicity can address particular inferential goals, but the appropriate approach depends on the analysis plan and the role of each outcome. No adjustment should be assumed. Since numerical results are not reported, the impact of multiplicity on any finding cannot be evaluated.

Information about missing primary-outcome observations, reasons for missingness, and methods for handling missing data is not reported in the registry record. The record also does not describe an analysis population, such as whether all enrolled participants or only those with complete measurements contributed to each analysis. Although enrollment was 17, the number contributing to each outcome or analysis is not stated. Details of exclusions, imputation, and sensitivity analyses are not reported in the registry record.

These omissions limit assessment of how the analyzed participants relate to those enrolled and whether uncertainty accounts for missing measurements. They also prevent reproduction of the analyses from the registry description alone.

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 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry lists serious adverse events and other adverse events separately for the two groups. For the Normal Weight group, 0 serious events were reported among 12 at risk, and 5 other events were reported among 12 at risk. For the Overweight group, 0 serious events were reported among 5 at risk, and 3 other events were reported among 5 at risk. No deaths are listed in either group, and no top serious-event terms are listed.

These are descriptive counts recorded for the groups; they are not a comparison showing that one group had greater or lower risk. The study is observational, the groups are not a like-for-like control comparison, and the numbers at risk differ. The record does not provide event-level details or specify whether the other-event counts represent people with at least one event or total events. The serious-event counts are zero in both groups, but that does not establish that an adverse event could not occur or provide a precise estimate of its frequency.

The safety entries should be read alongside the limited enrollment and the study's observational purpose. They do not establish a treatment safety profile, because the registry describes physiological monitoring rather than a treatment comparison.

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

This record is useful for understanding what the investigators set out to measure: blood pressure and other cardiovascular markers in a circadian protocol, with repeated assessment across resting and exercise conditions and by phase relative to DLMO. It also makes clear that the intended comparison concerned normal-weight and overweight participants, and that the study was observational rather than randomized.

The registry record does not report numerical blood pressure estimates, group contrasts, confidence intervals, or p-values. Therefore, it does not show the size or direction of a blood pressure difference or circadian pattern. It also does not establish whether resting and exercise measurements differed, or whether patterns varied by group. Statements about such results would go beyond the posted record.

The registry explicitly warns that insufficient enrollment and an imbalanced group distribution prevent full statistical interpretation. This is a central qualification, not a minor technical detail. Even a numerical association in this setting would be an observation in the enrolled groups, not evidence that weight status caused a blood pressure difference. The record does not identify an adjustment approach that would support a causal interpretation.

The study's stated value is as pilot data for future investigations and sample size estimation. That describes the intended role of the collected data; it does not mean the current record contains a complete result or a reliable estimate for every planned outcome. The analysis details, missing-data handling, and multiplicity approach are not reported in the registry record.

In short, the posted information documents a study design and measurement strategy and reports a caution about statistical interpretability. It does not provide sufficient numerical outcome information to judge an effect, its precision, or its consistency across conditions. It should not be read as evidence for or against any medical intervention.

13. Why This Trial Matters Statistically

The study highlights a design issue that arises whenever physiology varies over time: measurements taken at different circadian phases may not be interchangeable. Using a phase marker and repeated measurements can help organize observations around biological timing rather than clock time alone. The record describes how DLMO was used for this purpose, giving future researchers a concrete feature of the measurement plan to consider.

It also illustrates the distinction between the number of readings and the number of participants. Blood pressure was collected repeatedly, but repeated values from the same person do not equal an equivalent number of independent people. The statistical analysis needs to account for that dependence. The registry does not report the analysis model, so it is not possible to judge how this design feature was handled.

The explicit warning about insufficient enrollment and group imbalance is statistically important. It sets limits on interpretation before considering any estimate: precision may be limited, and group contrasts are not randomized. The record's pilot-data framing is appropriate context for reading the study aims and the absence of reported numerical results, without treating the study as a definitive test.

Finally, the broad set of outcomes and analyses makes transparency about prespecification and multiplicity relevant. The registry lists outcome measures and analyses but does not describe their mapping or a multiplicity strategy. This case therefore shows why detailed reporting of analysis methods, missing data, and estimates with uncertainty is necessary to assess what a complex repeated-measures study contributes.

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 principal trial-specific limitation stated in the registry is insufficient enrollment combined with an imbalanced group distribution. Enrollment was 17, but the registry does not report how many participants contributed usable blood pressure readings in each group. This prevents a direct assessment of group-specific information and precision.

The design is observational. The record says allocation was not stated and cautions that the arms are not a like-for-like control comparison. This limits causal interpretation of differences between the normal-weight and overweight groups. The registry does not report whether or how potential confounding factors were addressed.

Primary blood pressure results are not reported in the registry record. Means, standard errors, confidence intervals, and comparison estimates are absent, so the magnitude and precision of any observed pattern cannot be assessed. Although the record describes up to 7 measurements per participant across 5 days and a 4-hour phase-binning approach, it does not provide participant-level counts or describe how incomplete repeated measurements were handled.

The analysis model, adjustment variables, diagnostic checks, multiplicity approach, and analysis populations are not reported in the registry record. The record identifies 9 outcome measures and 4 analyses, but not the relationship between them or which comparisons were prespecified. The listed intervention description and arm descriptions do not provide enough detail to resolve these statistical reporting gaps.

These limitations are specific to interpretation of the registry record. They do not imply that no further information exists elsewhere; such information is not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Body Weight, Sleep, and Heart Health — NCT03388788.
• Registry record last updated 2026-11-04; status last verified 2026-10.
• Results first posted 2026-05-18.
• 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

NCT03388788 is a completed observational study sponsored by Oregon Health and Science University, with enrollment of 17. It examined circadian cardiovascular risk markers, with attention to obesity, using a 5-day protocol of repeated measurements. The primary outcome was mean blood pressure in mmHg, measured at rest and during exercise, and organized by weight group, exercise condition, and circadian phase relative to DLMO.

The registry describes positron emission tomography scanning of cardiac function at 3 time points across the 24 hour circadian cycle and lists secondary outcomes including coronary microvascular blood flux, flow mediated dilation, heart rate, epinephrine, norepinephrine, and cortisol. The record states that insufficient enrollment and imbalanced group distribution limit full statistical interpretation. Numerical primary blood pressure results and key analysis details are not reported in the registry record.