Lifestyle Intervention for Weight Gain Management for Patients With Schizophrenia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Lifestyle Intervention for Weight Gain Management for Patients With Schizophrenia (NCT01368406), a randomized na study. The primary outcome is Change in Weight From Baseline to Endpoint.

2. Clinical Question

This question concerns a continuous outcome: weight measured in kilograms. A comparison of the groups would help describe whether their average weight changes differed over the follow-up period. The registry record lists outcome summaries for each arm, but its analysis entries do not yield an estimable two-arm comparison. Consequently, the posted information does not give a clear estimate of the difference in average change between the wellness program and usual care, with an associated confidence interval. The available results need to be interpreted as incomplete evidence about the comparative effect, rather than as a definitive answer to the trial question.

3. Trial Design

This was a randomized, parallel-group clinical trial with single masking. It was conducted by the Federal University of São Paulo and listed as completed. The registry gives the study start as 2007-08 and primary completion as 2009-03. The enrolled population was 160 participants, assigned to a wellness program or treatment as usual. The registry lists 81 participants in the wellness-program arm and 79 in the usual-care arm for the primary outcome.

The wellness program was behavioral. It consisted of 12 weeks of weekly group meetings, each lasting 1 hour, with topics including dietary choices, lifestyle, physical activity and self-esteem. Outpatients and their relatives were included in the sessions as described in the registry. The comparator was regular visits with a psychiatrist. The registry does not describe additional elements of usual care or state whether the schedule of those visits was standardized.

The primary outcome was change in weight from baseline to 3-month follow-up. The record says participants were weighed in the morning on the same scale, without shoes and wearing light clothes, and that the same investigator collected measurements at all assessments. These details describe how weight was measured; they do not explain how missing measurements or deviations from the planned assessment schedule were handled.

The record does not report the masking procedures, the roles of masked personnel, the randomization sequence method, or allocation concealment. It also does not report a protocol-based sample-size justification or the statistical analysis plan. Although the trial description mentions metabolic profile, symptoms and quality of life as aims, no secondary outcome results are posted. The registry does not report whether the primary analysis followed intention-to-treat principles or used another analysis population.

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:

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 Weight From Baseline to Endpoint, measured over baseline, 3-month.

The primary endpoint was change in weight from baseline to 3-month follow-up, expressed in kilograms. Weight is a continuous measure, and the registry describes the reported arm-level parameter as a mean. The outcome addresses the trial's stated weight-management aim by tracking how weight changed during the interval between the baseline assessment and the endpoint assessment.

The measurement procedure was described in some detail. Participants were weighed in the morning, on the same scale, without shoes and wearing light clothes. The same investigator collected measurements at each assessment. Consistent conditions and a consistent assessor can reduce some sources of variation in measurement, although the record does not quantify measurement reliability or report whether assessors knew participants' assignments.

For a comparative question, the key result would be the difference in average weight change between the randomized groups, together with a measure of its uncertainty. An arm's average change alone does not establish whether the intervention group changed differently from the control group. The registry's posted outcome summaries give an average value and confidence limits for each arm, but the record does not provide an estimable two-arm comparison for this continuous endpoint. It also does not clarify the analysis population or explain how missing endpoint measurements were handled. Those omissions limit how directly the posted endpoint summaries can answer the comparative question.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The endpoint is continuous because weight is measured on a numerical scale in kilograms. The registry identifies the arm-level parameter as a mean. A mean describes the average value in the analyzed group, but its interpretation depends on which participants contributed measurements and how the change was calculated. The record says the endpoint covers baseline to 3-month follow-up, but it does not explain the calculation in enough detail to determine how participants without a measurement at either assessment were treated.

What does a confidence interval communicate?

A confidence interval presents a range of values compatible with an estimate under the statistical method and assumptions used. A narrower interval generally indicates greater precision than a wider interval, while an interval that covers a broad range leaves more uncertainty about the underlying value. An interval is not a prediction range for individual participants and does not guarantee that the true effect lies within its limits. The registry reports 95% confidence intervals for the arm-level summaries and for its listed analyses, but it does not provide an estimable two-arm comparison interval for the primary continuous endpoint.

Why is the between-arm contrast important?

Randomization creates groups intended for comparative evaluation. The question is whether the average change differs between those groups, not merely whether a change within either group can be distinguished from zero. A contrast between groups would express the estimated difference in their outcomes, with uncertainty around that difference. Arm-specific means and confidence intervals do not automatically give the uncertainty of the contrast, because that uncertainty depends on the variability and relationship of the observations used in the analysis. The registry marks the two-arm comparison as missing or not estimable, so a recalculated comparative estimate is not available.

How should a t-test and p-value be read?

A t-test is a method for evaluating a hypothesis about a mean or a difference in means, subject to its assumptions and the way the comparison is defined. A 2-sided test considers departures in either direction. A p-value describes how incompatible the observed data are with a specified null hypothesis under the test's assumptions; it is not the probability that the null hypothesis is true, nor the probability that a treatment works. The registry lists p = 0.055 for each of its two analyses. Because these entries are attached separately to the arms and the intended contrast is not clarified, those values should not be interpreted as an unambiguous test of the primary between-arm question.

Why can variation and measurement details matter?

Continuous outcomes vary among participants, and the amount of variation affects the precision of a mean and of a group comparison. The same scale, morning measurement, similar clothing conditions and consistent assessor can reduce avoidable measurement variation. They do not remove genuine differences among participants, nor do they establish that all measurements were available or collected without knowledge of assignment. The registry does not report the dispersion for the wellness-program arm, and it does not explain the differing interval widths accompanying the two arm-level means.

In general, over-dispersion describes greater variability than a statistical model anticipates. When a model underestimates variability, standard errors may be too small and confidence intervals too narrow; a suitable method can account for extra variability. The record does not state that over-dispersion was assessed or that it was relevant to this continuous endpoint. No conclusion about such a problem can be drawn from the posted information.

What does a sample-size illustration mean?

A planning illustration based on an observed effect is not an observed trial result and is not observed power. The registry's planning assumptions specify a 2-sided significance level of 0.05, equal allocation, a normal approximation and effects defined as fractions of the observed effect. No resulting sample-size values are reported in the registry record. The record also does not report the trial's own sample-size justification, the effect size used in its design, or whether the study had interim analyses. A planning calculation made from an observed estimate cannot substitute for those design details.

Finally, interpretation depends on the analysis population and the handling of incomplete data. If participants lack endpoint measurements, the choice to exclude them, model their available data or use another strategy can affect the estimate and its uncertainty. The registry does not report the missing-data approach or identify the population used for the primary analysis. The posted methods therefore support only a limited reading of the outcome summaries and reported tests.

10. Analyses Reported by the Sponsor

The registry lists two sponsor-reported analyses, both described as 2-sided t-tests. The wellness-program entry gives a mean difference in final values of -0.48, with a 95% confidence interval from -0.65 to 1.13 and p = 0.055. The treatment-as-usual entry gives 0.48, with a 95% confidence interval from 0.13 to 0.83 and p = 0.055.

Those entries are presented separately for the two arms, and the registry does not explain how they represent the comparison between randomized groups. The arm-level outcome summaries report a mean of 0.48 for each group. The record also states that a two-arm comparison for the continuous endpoint was missing or not estimable. As a result, there is no recalculated between-arm estimate to compare directly with the sponsor's analyses. The registry record does not clarify the relationship among the listed arm-level means, analysis entries and the intended primary contrast. Readers should avoid treating either arm-specific entry as a clear estimate of the difference between groups.

11. Multiplicity, Missing Data and Analysis Populations

The trial description states that the investigators aimed to evaluate weight management as well as effects on metabolic profile, symptoms and quality of life. The registry posts one outcome measure and no secondary outcome results. It lists two analyses for the primary outcome, but does not explain why both are reported or specify whether either represents the planned primary test. The analysis plan and any prespecified hierarchy of outcomes or contrasts are not reported in the registry record.

Multiplicity arises when several outcomes, comparisons or analyses are considered. If many statistical tests are conducted, the chance of at least one apparently notable result can increase unless the testing strategy is taken into account. General methods for addressing multiplicity include prespecifying a primary contrast, controlling an overall error rate or treating secondary findings as exploratory. The registry does not report whether multiplicity was considered, or whether any adjustment was used. The number of posted measures alone cannot establish the full scope of analyses conducted.

The record also does not state how missing data were handled, whether participants were analyzed according to their randomized assignment, or which analysis population was used. The primary outcome's population field is blank. These details are important because the participants included in an analysis and the treatment of incomplete follow-up can influence estimates and their precision. The registry specifically says that values for a two-arm comparison of the continuous endpoint were missing or not estimable, which further limits interpretation of the primary question.

No interim analyses or stopping rules are reported in the registry record. Their absence from the record should not be read as evidence that none occurred. The same caution applies to the analysis plan and missing-data procedures: without documentation, their role cannot be assessed. The posted information does not support claims about adjustment, prespecification or the completeness of outcome follow-up.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

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 zero participants affected by serious adverse events in the wellness-program arm and zero in the treatment-as-usual arm. It also reports zero participants affected by other adverse events in both arms. These are counts as recorded for the listed groups; the record does not provide descriptions of specific serious adverse-event types.

The deaths field is not reported for either group. It should not be read as a reported count of zero deaths. The registry also does not give further detail about how adverse events were collected, the observation period for safety outcomes, or how events were judged to be related to the intervention. Counts of zero in the posted fields do not establish that no events occurred outside the recorded categories or observation procedures. They describe only the safety figures entered in the registry record, and they do not by themselves support a broader conclusion about safety.

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

The posted outcome summaries describe mean weight changes over the interval from baseline to 3-month follow-up. The wellness-program arm is listed with a mean of 0.48 kg and a 95% confidence interval from -0.65 to 1.13. The treatment-as-usual arm is listed with a mean of 0.48 kg and a 95% confidence interval from 0.13 to 0.83. The registry's separate analysis entries report p = 0.055 for each arm, but do not clearly identify an interpretable test of the between-group difference.

These results do not amount to a clearly reported estimate of the comparative effect of the wellness program. The record states that an estimate for a two-arm comparison of the continuous endpoint was missing or not estimable. Without that contrast, the arm-level summaries cannot establish how much the groups differed in average weight change or how precisely that difference was estimated. The differing confidence intervals and the separate analysis entries also require caution because their relationship is not explained.

The findings do not show whether the intervention changed metabolic profile, symptoms or quality of life; no secondary results are posted. Nor do the registry's safety counts establish that no adverse events occurred beyond the recorded categories. Deaths are not reported. These limits concern what can be concluded from the registry record, rather than whether the intervention is appropriate for any individual.

More generally, a trial result is an estimate based on a particular study population, measurement schedule, analysis method and follow-up. The record describes weight measurement conditions but does not report the analysis population, missing-data handling or the full statistical plan. Thus, the posted information offers a limited account of the primary outcome and does not settle the broader clinical aims described for the study.

14. Why This Trial Matters Statistically

This trial illustrates a central distinction in clinical-trial interpretation: a group-level outcome summary is not the same as a comparison between randomized groups. The primary question concerns whether average weight change differed between the wellness program and treatment as usual. The registry gives arm-specific means and confidence intervals, but identifies the two-arm comparison as missing or not estimable. A reader therefore cannot use the arm summaries alone as a substitute for the comparative estimate.

The record also demonstrates why the meaning of a reported p-value depends on a clearly described hypothesis and analysis. The two listed tests have the same p-value, but each is associated with a single arm, and the registry does not explain how the entries relate to the primary comparison. Presenting a number without a clearly interpretable contrast can make a result appear more conclusive than the record supports.

Measurement procedures are another useful statistical consideration. Consistent timing, equipment, clothing conditions and assessor may reduce avoidable variation in a continuous outcome. Yet careful measurement does not resolve missing endpoint data or replace a defined analysis population. Those features also shape the precision and meaning of an estimate.

Finally, the trial's stated aims extend beyond weight, while no secondary results are posted. This distinction matters when separating an outcome that has numerical results from other questions named in a study description. The record is informative about design and measurement, but its incomplete comparative reporting and absent secondary findings limit the conclusions that can be drawn.

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.

A specific limitation is that the registry does not provide an estimable two-arm comparison for the primary continuous endpoint. The arm-level mean values are both reported as 0.48, but the confidence intervals differ, and the separate analyses list -0.48 for the wellness program and 0.48 for treatment as usual. The registry does not explain how these entries relate to one another or to the intended between-group question. This makes it difficult to interpret the reported tests as direct evidence about the primary comparison.

The record does not report dispersion for the wellness-program arm. It also does not identify the primary analysis population, explain how missing outcome measurements were handled, or provide details of the statistical analysis plan. Although the measurement procedure is described, assessor masking is not reported. The registry identifies the trial as single-masked but does not say which parties were masked or how masking was maintained.

Other limitations in the available record include the absence of secondary outcome results despite the study description's aims concerning metabolic profile, symptoms and quality of life. The deaths field is not reported, and the registry does not describe adverse-event collection or follow-up procedures. It also does not report a protocol-based sample-size justification, interim analyses or a multiplicity strategy. These are limitations of the information available in the registry record; they do not establish that the procedures were absent from the study itself.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Lifestyle Intervention for Weight Gain Management for Patients With Schizophrenia — NCT01368406.
• Registry record last updated 2013-05-22; status last verified 2013-04.
• Results first posted 2013-05-22.
• 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

NCT01368406 is a completed randomized, parallel-group, single-masked trial sponsored by the Federal University of São Paulo. It enrolled 160 participants and compared a 12-week wellness program with treatment as usual, described as regular psychiatrist visits. The primary outcome was change in weight from baseline to 3-month follow-up, measured in kilograms.

The record lists arm-level mean changes and two separate 2-sided t-test analyses, but says a two-arm comparison for the continuous endpoint was missing or not estimable. The analysis population, missing-data approach and statistical plan are not reported in the registry record. No secondary results are posted. Serious and other adverse-event counts are recorded as zero in both arms; deaths are not reported.