The Louisiana (LA) Health Project: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Louisiana (LA) Health Project (NCT00289315), a randomized na study. The primary outcome is % Body Fat (Boys).

2. Clinical Question

3. Trial Design

The Louisiana (LA) Health Project is registered as a randomized, parallel-group behavioral study. The registry also identifies the design as cluster-randomized. In a cluster-randomized trial, groups or settings, rather than individual participants, are assigned to study arms. The particular unit of assignment, the number of clusters, and the methods used to recruit participants within clusters are not reported in the registry record.

The three arms were primary environmental weight-gain prevention, combined primary environmental and secondary behavioral weight-gain prevention, and control. The control arm is described as having no environmental or behavioral program intervention. The registry does not report how the programs were delivered, how long participants received them, or whether the control group had access to other activities or services.

The registry reports enrollment of 2060 and lists the study status as completed. The study start is recorded as 2005-08, with primary completion in 2009-05. Pennington Biomedical Research Center is identified as the sponsor. The study is listed under childhood obesity, and its stated overall focus is primary and secondary obesity prevention in children and adolescents.

The primary outcome is percent body fat in boys, measured as change between baseline and 3 years. The registry lists four outcome measures, but it reports zero analyses. The result for the primary outcome and the results for the other outcome measures are not reported in the registry record. Details of the randomization procedure, allocation concealment, participant flow, and follow-up completeness are also 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: children in primary prevention, primary + secondary prevention, and control group (boys)

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.

Population: Only participants with complete data (baseline and at least one of two follow-up measurements) were included in the analysis.

6. Primary Endpoint

The registry lists the primary outcome as % Body Fat (Boys), measured over Baseline and 3 years.

Percent body fat is a continuous measure: it describes the proportion of body mass made up of fat, expressed as a percentage. The primary endpoint is the change in this measure between baseline and 3 years for boys in the three study groups. It therefore concerns change over time, rather than a single measurement at baseline or follow-up alone.

In general, a continuous endpoint can retain information about variation across participants instead of reducing outcomes to categories. A change measure can also describe how a group’s average measurement shifts over the specified follow-up period. For this study, the registry specifies the mean as the summary parameter and standard error as the dispersion measure. A standard error describes the precision of an estimated mean; it is not the spread of individual participants’ values.

Body fat percentage is relevant to a study focused on obesity prevention because it measures body composition, rather than body weight alone. That general rationale does not establish that this endpoint captures every aspect of health or that a particular change is clinically important. The registry does not report a threshold for meaningful change, the observed mean changes, their standard errors, or a comparison between groups. The endpoint’s results and precision therefore cannot be evaluated from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes the primary outcome as a mean change in a continuous measure. A mean summarizes the center of a set of measurements, while a standard error describes the precision of an estimated mean. These quantities answer different questions: the standard error does not describe how much individual children vary in body fat percentage. The registry names standard error as the dispersion measure, but does not report its value for the primary outcome.

What does a change endpoint represent?

A change endpoint compares a follow-up measurement with a baseline measurement for the same outcome. In general, comparing changes can help describe whether groups followed different trajectories over time. Interpretation depends on the actual group estimates and on how the analysis handles repeated measurements and participant follow-up. The registry states that the outcome is change from baseline to 3 years, but the calculation details and results are not reported in the registry record.

Why does cluster randomization matter?

In general, cluster randomization assigns groups or settings rather than assigning every participant independently. Outcomes from people in a shared cluster can be correlated because they share circumstances or exposure to the intervention. This correlation means that the amount of independent information may be less than an analysis treating every participant as unrelated would imply. Appropriate analysis needs to account for the cluster structure, and uncertainty estimates should reflect it.

The registry identifies this study as cluster-randomized and specifically cautions that a simple individual-level re-analysis would be misleading. It also states that only the sponsor’s own analysis is shown. However, the registry lists zero analyses, and no sponsor analysis of the primary outcome is reported in the registry record. The cluster definition, number of clusters, within-cluster correlation, and analysis method are not reported in the registry record, so the adequacy of any adjustment cannot be assessed.

How should uncertainty be read?

In general, an estimate describes the observed effect, while a confidence interval communicates the range of values reasonably compatible with the data under the analysis assumptions. A narrow interval indicates greater precision than a wide interval, but neither interval width nor an estimate alone establishes clinical importance. A p-value addresses compatibility with a specified null hypothesis under a statistical model; it does not measure the probability that the null hypothesis is true or the size of an effect.

No confidence interval, p-value, or effect estimate for the primary outcome is reported in the registry record. Accordingly, neither statistical significance nor precision can be assessed. There is also no reported sponsor analysis to compare with a recalculation from summary statistics. No recalculated outcome estimates are available in the registry record.

What do the planning assumptions mean?

Sample-size planning asks how many participants may be needed to detect an effect under stated assumptions. The registry’s planning description specifies a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It describes the target effect as a stated fraction of the observed effect. These are assumptions for planning illustrations, not evidence about the study’s observed findings or its original design.

Planning figures based on an observed effect can change depending on the assumed effect size and analysis model. In general, a smaller effect to detect requires more information than a larger effect to detect, all else equal. This general principle does not supply a study-specific sample-size estimate. The observed effect and the planning values are not reported in the registry record. The stated illustration assumptions also do not establish that the original study used those methods, and the registry does not report a sample-size justification or original power calculation.

Why might over-dispersion matter?

In general, over-dispersion describes data that vary more than a model assumes. It can make standard errors too small if the model fails to allow for the extra variability. The primary endpoint is continuous, and the registry specifies a mean with standard error; it does not report that an over-dispersion model was used or that over-dispersion was assessed. For this cluster-randomized design, the central documented concern is dependence among participants within clusters, which must be handled in the analysis. The specific variance model is not reported in the registry record.

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("Arm 1", "Arm 2", "Arm 3")
n   <- c(292, 312, 235)
m   <- c(-1.3, -2, -0.11)
sp  <- c(0.59, 0.54, 0.68)
sd  <- sp * sqrt(n)      # standard errors converted to SDs
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  Arm 1  292  -1.300  10.082  -2.461  -0.139
CARM  Arm 2  312  -2.000  9.538  -3.063  -0.937
CARM  Arm 3  235  -0.110  10.424  -1.450  1.230

11. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures, but it does not describe how the study handled multiple outcomes or multiple comparisons. In general, testing several outcomes or several group contrasts can increase the chance of finding at least one apparently notable result by chance. Multiplicity procedures may address that issue, but the appropriate approach depends on the prespecified questions and analysis plan. Neither a multiplicity adjustment nor a hierarchy of outcomes is reported in the registry record.

Although the primary outcome is identified, the statistical analysis plan, prespecified contrasts, and any interim analyses are not reported in the registry record. The registry lists zero analyses, so it does not provide results with which to assess the relationship between planned and reported analyses. Whether outcomes or analyses were changed after the study began is not reported in the registry record.

Missing data can affect estimates when participants lack baseline or follow-up measurements. In general, the impact depends on how much information is missing and why it is missing; methods such as imputation or complete-case analysis rely on assumptions that should be described. The registry does not report missingness by arm, reasons for missing measurements, a missing-data method, or sensitivity analyses. Follow-up completeness for the primary outcome is not reported in the registry record.

The analysis population is also unspecified. The registry does not report whether the primary outcome analysis included all participants as randomized, only those with available measurements, or another population. Details of adherence, crossover, exclusions, and participant flow are not reported in the registry record. These omissions limit assessment of how the randomized design was carried through to the outcome analysis.

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 registry reports serious adverse-event counts, other adverse-event counts, and deaths separately for each study arm. For Arm 1, the number at risk is 713 for both event categories, with zero serious adverse events, zero other adverse events, and zero deaths. For Arm 2, the number at risk is 760 for both event categories, with zero serious adverse events, zero other adverse events, and zero deaths. For Arm 3, the number at risk is 587 for both event categories, with zero serious adverse events, zero other adverse events, and zero deaths.

These entries describe what the registry records; they do not by themselves establish that every possible event was identified or that safety follow-up was complete. The registry does not report definitions of serious or other adverse events, the method or duration of safety surveillance, or whether event collection differed across arms. It also does not list serious adverse-event terms. Zero recorded events should therefore be interpreted as a registry count, not as proof that an intervention is risk-free.

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

The registry describes a randomized, cluster-randomized comparison of primary environmental prevention, combined primary and secondary prevention, and a control condition. It identifies change in boys’ percent body fat between baseline and 3 years as the primary outcome. These details establish the study question and the broad design, but they do not establish the result.

The registry does not report the primary outcome’s group estimates, standard errors, a between-group comparison, or any inferential statistics. It lists four outcome measures and zero analyses. Consequently, the posted information does not show whether body fat percentage changed differently across groups, how large any difference was, or how uncertain an estimate would be. It also cannot establish the findings for outcomes other than the primary endpoint.

Likewise, the safety counts describe zero recorded events in each arm, but the registry does not provide information about the completeness or conduct of safety monitoring. Those counts do not establish that no adverse events occurred beyond the recorded entries, nor do they demonstrate comparative safety.

In general, trial findings are interpreted in light of the intervention, population, outcomes, analysis methods, and uncertainty. Here, important details—including the cluster-level analysis, missing-data handling, analysis populations, and multiplicity procedures—are not reported in the registry record. The study’s completion status and enrollment do not fill those gaps. Without results and analysis details, no conclusion about the direction, magnitude, precision, or practical importance of an intervention effect can be drawn from the registry record.

14. Why This Trial Matters Statistically

This study raises a useful statistical issue: randomization can occur at a group or setting level even when outcomes are measured for individual participants. When assignment is clustered, a valid analysis needs to respect that structure. Treating every participant as statistically independent can understate uncertainty and make comparisons appear more precise than the design supports. The registry explicitly notes this concern and rules out a simple individual-level re-analysis as misleading.

The outcome also illustrates the difference between defining a question and reporting its answer. The registry specifies a continuous primary endpoint, its population, and its interval of measurement. Those details help clarify what an analysis should estimate. But a defined endpoint without an estimate, measure of uncertainty, and analysis description cannot support an evidence-based interpretation of the comparison.

There is a further distinction between a study’s observed findings and planning illustrations. Sample-size calculations depend on assumptions about the effect to detect and the analysis. The registry describes an illustration based on the observed effect, but does not report the effect or the illustration results. Such calculations are not observed power and do not replace the study’s outcome analysis.

Finally, reporting the number at risk alongside event counts helps readers understand the context of safety entries, while the absence of monitoring details limits what can be inferred from zero counts. Together, these features show why clear reporting of the design, analysis, uncertainty, missing data, and outcome ascertainment matters for interpreting clinical research.

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 limitation for interpreting the study from the registry record is that it identifies the primary endpoint but does not report the outcome analysis. No group-level change, standard error, contrast, confidence interval, or test result is reported. Although four outcome measures are listed, the registry records zero analyses. This prevents assessment of effect direction, magnitude, precision, or consistency across outcomes.

The cluster-randomized design requires analysis that accounts for clustering. The registry cautions against simple individual-level re-analysis and says only the sponsor’s own analysis is shown, yet the record lists zero analyses. Details needed to evaluate cluster adjustment—including the assignment unit and analysis approach—are not reported in the registry record.

Other design and reporting details are also unavailable: the recruitment setting, eligibility criteria, allocation procedure, participant flow, follow-up completeness, intervention delivery, and control-group services are not reported in the registry record. The analysis population, missing-data methods, multiplicity approach, and any interim analyses are not reported in the registry record either.

Safety interpretation is limited by the absence of event definitions, ascertainment methods, and follow-up details. The zero event counts cannot establish the completeness of reporting. Finally, the planning assumptions do not document the original design justification, and the observed effect used for the planning illustration is not reported in the registry record. These limitations concern the information available in the registry, not necessarily the full study documentation.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: The Louisiana (LA) Health Project — NCT00289315.
• Registry record last updated 2018-07-10; status last verified 2018-06.
• Results first posted 2018-06-12.
• 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 Louisiana (LA) Health Project is a completed randomized, cluster-randomized, parallel-group behavioral study sponsored by Pennington Biomedical Research Center. The registry reports enrollment of 2060, a start of 2005-08, and primary completion in 2009-05. Its three arms were primary environmental weight-gain prevention, combined primary environmental and secondary behavioral prevention, and control with no environmental or behavioral program intervention.

The primary outcome is mean change in boys’ percent body fat from baseline to 3 years, with standard error specified as the dispersion measure. The registry lists four outcome measures and zero analyses. Primary outcome results, analysis methods, missing-data handling, and multiplicity procedures are not reported in the registry record. The safety entries record zero serious adverse events, zero other adverse events, and zero deaths in each arm, with arm-specific numbers at risk. The record’s cluster-randomization warning means an individual-level re-analysis would be misleading; the sponsor’s own analysis is not reported.