Translating a Heart Disease Lifestyle Intervention Into the Community: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Translating a Heart Disease Lifestyle Intervention Into the Community (NCT01647438), a randomized na study. The primary outcome is Change in Physical Activity (Minutes/Week).

2. Clinical Question

3. Trial Design

This was a randomized, parallel-group study with single masking, sponsored by Northwestern University. The registry lists the study as completed. It describes two assignments: lifestyle intervention and primary care referral with print health education. The enrollment recorded in the registry is 63. The outcome results list 32 participants in the comparator group and 31 in the lifestyle-intervention group; the registry does not provide further detail on how the outcome-analysis populations were determined.

The intervention combined six weekly health education classes with phone counseling. The comparator received print health education materials and was described as receiving primary care referral. The study was designed to evaluate feasibility and initial effectiveness of a community-based, culturally targeted lifestyle intervention for cardiovascular health among underserved South Asian Americans. The registry does not report a specific operational definition or numerical threshold for feasibility.

The primary outcome was change in physical activity from baseline, measured by accelerometer and expressed in minutes per week at 6-months. Results are presented as group means with standard errors, alongside a mean difference and confidence interval. The registry identifies the design as single-masked but does not say which people were masked or how masking was maintained. Further details of random sequence generation, allocation concealment, protocol deviations, and the trial's original statistical plan are not reported in the registry record.

The registry records a start date of 2012-08 and primary completion in 2013-12. Those dates describe the study timeline, not the duration of follow-up for every participant. The reported primary outcome timeframe is baseline and 6-months. The record does not establish whether all randomized participants had an outcome measured at that time.

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

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 Physical Activity (Minutes/Week), measured over baseline and 6-months.

The primary endpoint measures change in physical activity from baseline to 6-months, expressed as minutes per week. Physical activity was measured by accelerometer, an objective measurement approach that records movement rather than relying solely on participants' recall. The registry identifies the endpoint as a continuous measure and reports group means and standard errors.

Change from baseline is used to describe how the measured activity level shifted over the follow-up period. Comparing the average changes between randomized groups addresses whether the observed change differed between the lifestyle-intervention assignment and the primary care referral and print-material assignment. A mean difference summarizes that contrast in the same units as the outcome, making its magnitude interpretable in minutes per week.

The registry does not report how accelerometer wear time was handled, how a valid measurement was defined, or how missing device readings were treated. It also does not report whether the measure was adjusted for baseline physical activity or other participant characteristics. These details matter when interpreting the measurement process, but should not be inferred from the endpoint description alone.

7. Results Posted in the Registry

• Lifestyle Intervention: mean 10.00 versus 4.00 on control; difference 6.00 (95% CI -34.22 to 46.22), standardized effect d = 0.07; z-test p = 0.770.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: it is measured in minutes per week, and the registry summarizes each group's change using a mean. The principal contrast is a difference between group means. In plain terms, it subtracts the average change in the comparator group from the average change in the lifestyle-intervention group. A positive estimate means the intervention group's average change was higher; a negative estimate would mean it was lower. This direction describes the statistical contrast and does not by itself establish a beneficial or harmful effect.

What do the standard errors describe?

A standard error describes the uncertainty in an estimated quantity, such as a group mean. It is not the same as the standard deviation, which describes variation among individual observations. The reported standard errors are 14.0 min/week for the primary care referral and print health education group and 15.0 min/week for the lifestyle-intervention group. They indicate that the group mean estimates have appreciable uncertainty. The registry does not report the standard deviations for the outcome groups or the underlying participant-level observations.

For a mean difference, uncertainty depends on the uncertainty in each group's mean and on the comparison method. The registry reports the estimated difference together with a confidence interval and an unadjusted p-value. The record does not describe a covariate-adjusted model, the handling of outliers, or whether any assumptions were checked. It is therefore not appropriate to attribute the posted comparison to a more elaborate model than the record describes.

How should a confidence interval be understood?

A confidence interval gives a range of values compatible with the data and the method's assumptions. It communicates both the direction and the precision of an estimate. A narrow interval indicates greater precision than a broad one. If an interval for a mean difference includes zero, the data do not rule out no average difference at the confidence level used. The interval extends from -34.22 to 46.22 min/week, so it includes zero as well as differences in either direction. The registry does not state the confidence level or provide the detailed calculation method for this interval.

What does the p-value add?

The p-value is a measure of how compatible the observed data are with a specified null model, under the statistical assumptions of the test. The posted unadjusted p-value is 0.77. It is not the chance that the intervention is ineffective, and it does not measure the size or practical importance of a difference. Reading the p-value together with the estimated mean difference and interval gives a more complete account: the point estimate is 6.0 min/week, but its uncertainty is wide enough to include a range of possible contrasts.

Because the record gives an unadjusted comparison, it does not establish whether adjustment for baseline values or other factors was part of the trial's original analysis. The registry does not report the prespecified statistical test, transformations, model diagnostics, or a detailed analysis plan. The sample-size illustration uses a normal approximation, but that planning assumption should not be mistaken for documentation of the original outcome-analysis method.

Why does variability matter?

When individual outcome measurements vary considerably, a group mean can be estimated less precisely unless the study has enough information to offset that variability. General statistical principle: greater variability relative to the effect being studied makes it harder to distinguish a group contrast from random variation. For this outcome, the registry supplies standard errors and a pooled standard deviation in the comparison information, but the standard errors and confidence interval are the clearest direct descriptions of uncertainty around the posted group means and contrast. No separate distributional assessment is reported.

Over-dispersion is a concern in some outcome models when observed variability exceeds what a model assumes. It is most often discussed for count outcomes. The primary outcome is continuous, and the registry does not report a count model or an over-dispersion assessment. That concept should not be applied as though it were a documented problem in this analysis. More generally, model assumptions matter because the precision estimates and tests are reliable only to the extent that the chosen method is suitable for the data.

What is not established by the record?

The registry lists no posted analyses beyond the primary outcome record and reports no posted secondary outcomes. It does not report the analysis population, the number with an observed primary outcome, a missing-data method, a protocol-defined handling of adherence, or an adjusted effect estimate. It also does not report whether interim analyses were planned or performed. These absences limit the ability to assess whether the posted result follows a prespecified analysis plan or how incomplete measurements may have affected the result. They are reporting gaps, not evidence that a particular method was or was not used.

10. Confidence Intervals and Precision

The estimated mean difference in change in physical activity was 6.0 min/week for lifestyle intervention relative to primary care referral and print health education. The confidence interval ranged from -34.22 to 46.22 min/week. This is a broad interval in relation to the point estimate, indicating limited precision. It includes zero, negative differences, and positive differences larger than the estimate.

The interval conveys a range of contrasts that remain compatible with the reported data and the method's assumptions. Its lower end allows for the intervention group to have had a smaller average change than the comparator; its upper end allows for a larger average change. The point estimate alone would conceal this uncertainty. The interval does not mean that every value inside it is equally plausible, nor does it guarantee that the true effect lies within the interval.

The registry does not state the confidence level or provide enough detail to independently reconstruct the interval method. The reported group standard errors are 14.0 min/week and 15.0 min/week. Those values reinforce that the mean estimates themselves are uncertain, but they are not measures of the range of individual activity changes. The pooled standard deviation listed for the comparison is 81.35; the record does not present participant-level data that would allow a fuller assessment of the outcome distribution.

The interval should be considered with the unadjusted p-value of 0.77 and the trial's design and reporting limits. Taken together, the result does not narrowly pin down the size or direction of the average contrast. It should not be read as proof of no difference, and the interval does not establish that the groups are equivalent. No equivalence margin is reported.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size figures are planning illustrations, not observed study results. They give participants per arm, rather than a total number of events. The calculation assumes a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It uses the observed effect as its reference and considers detecting the stated fraction of that effect. These are assumptions for the illustration; the trial's own original design assumptions are not reported in the registry record.

The 80% power column gives the estimated participants per arm for a planning scenario designed to have an 80% chance of detecting the chosen effect under the stated assumptions, if that effect is the true one. The 90% power column gives the corresponding planning figure for a 90% chance. These are design calculations, not statements about the probability that the observed result is correct or that the intervention has an effect.

The rows consider planning for 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. For 100% of the observed effect, The table shows 2,886 participants per arm for 80% power and 3,864 participants per arm for 90% power. For 75% of the observed effect, it lists 5,131 participants per arm for 80% power and 6,868 participants per arm for 90% power. For 50% of the observed effect, it lists 11,543 participants per arm for 80% power and 15,453 participants per arm for 90% power. Smaller effects require more participants under these assumptions, because a smaller contrast is harder to distinguish from random variation.

This is not observed power. The table cannot change the uncertainty in the completed trial's estimate or explain why its result was imprecise. The registry does not report the original sample-size justification, so these figures should not be presented as the trial's planned enrollment target.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 6.000; pooled standard deviation σ = 81.349.
2. n = 2 × (1.96 + 0.842)² × 81.349² / 6.000² = 2,885.7, rounded up to 2,886 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 6                      # observed difference in means
sigma <- 81.349478823887                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(1647438)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 2,886 (80% power), 3,864 (90% power)
 75% of observed effect: n per arm = 5,131 (80% power), 6,868 (90% power)
 50% of observed effect: n per arm = 11,543 (80% power), 15,453 (90% power)
power.t.test: 2886.6 
Simulated power at n = 2,886 per arm: 0.797 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome, change in physical activity in minutes per week, and reports zero posted secondary outcomes. It also records zero posted analyses. The primary comparison is accompanied by an unadjusted p-value. The registry does not report a multiplicity strategy, such as a procedure for controlling error across multiple outcomes or repeated tests. With no secondary outcomes posted, the record does not permit assessment of how many outcomes or analyses may have been considered during the study.

Missing-data handling is not reported in the registry record. The outcome description specifies accelerometer measurement at baseline and 6-months, but does not state how participants without measurements at either time were handled, whether measurements were excluded for insufficient device wear, or whether any values were imputed. The numbers listed with the outcome results do not, by themselves, establish how many randomized participants had complete measurements or whether those numbers represent an intention-to-treat population.

The analysis population is not reported. The record does not say whether the primary result used all randomized participants, participants with available measurements, or another defined group. It also does not describe treatment adherence, crossover, withdrawal, protocol deviations, or how these factors entered the analysis. Those omissions make it difficult to judge whether the comparison preserves the benefits of random assignment in the analysis.

The trial is described as single-masked, but the identity of the masked parties and the role of masking in outcome measurement are not reported. The registry also does not report interim analyses, stopping rules, or the original statistical plan. These details are relevant to understanding how the primary result was selected and interpreted. Their absence should be treated as a limitation of the record rather than evidence that any particular procedure was used.

14. 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 serious adverse events among 32 participants at risk in the primary care referral and print health education group and zero among 31 participants at risk in the lifestyle-intervention group. It also reports zero other adverse events among 32 and 31 participants at risk in those respective groups. The record lists no serious adverse-event terms.

These figures describe events recorded in the registry, not proof that no harm occurred. The registry does not report how adverse events were defined, how they were collected, the observation period for safety reporting, or whether events were assessed for relation to the intervention. Death counts are not reported in the registry record. The recorded zero counts should therefore be interpreted as no events posted in these categories, not as a complete assessment of safety or as evidence that the groups had identical risks.

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

The registry's primary result is an estimated mean difference of 6.0 min/week in change in accelerometer-measured physical activity, favoring a greater average change in the lifestyle-intervention group relative to the comparator. The confidence interval, from -34.22 to 46.22 min/week, is wide and includes no difference as well as differences in either direction. The unadjusted p-value is 0.77. Together, these statistics indicate that the posted data do not estimate the group contrast precisely.

The result does not establish that the intervention changed physical activity, and it also does not establish that there was no difference. A nonsignificant p-value is not evidence of equivalence. The registry does not provide an equivalence margin, a non-inferiority objective, or a formal feasibility result. The brief study description says the study was intended to evaluate feasibility and initial effectiveness, but the posted primary outcome alone cannot answer every part of that broader aim.

The estimate applies to the reported endpoint and the study groups as described. It should not be extended to outcomes that were not posted, to longer-term activity, or to all South Asian communities or other populations without further evidence. The registry does not report enough about recruitment, participant characteristics, adherence, missing measurements, or the analysis population to assess how representative the analyzed participants were or how those factors may have influenced the result.

The safety figures record zero serious and zero other adverse events in both groups, but the record's safety definitions and collection details are not reported. Those counts should not be taken as a guarantee of safety. Overall, the posted data give a point estimate and a substantial range of uncertainty for the primary outcome; they do not justify a definitive claim that the intervention works or does not work.

16. Why This Trial Matters Statistically

This trial raises statistical questions that are common in community-based behavioral research. The primary outcome is measured continuously and objectively by accelerometer, but the group comparison remains uncertain: its confidence interval spans negative and positive differences. This illustrates why reporting an estimate and its precision is more informative than relying on a p-value alone.

The study also concerns delivery of an intervention in a particular community context. Random assignment supports a comparative design, while the registry's description of culturally targeted classes and phone counseling makes implementation relevant to interpretation. Yet the record does not report class attendance, counseling engagement, or a formal feasibility result. A reader therefore cannot distinguish an intervention's potential under full participation from the result of the program as delivered in this study.

Planning for a future study depends on the effect size considered meaningful, the uncertainty around the observed estimate, and the design assumptions. The illustration shows that smaller assumed effects require more participants under its stated assumptions. Because the current estimate is imprecise and the original design rationale is not reported, the illustration should inform statistical planning cautiously rather than be treated as a definitive enrollment prescription.

Finally, gaps in reporting about missing measurements, analysis populations, and the statistical plan constrain reproducibility and assessment of bias. These are not merely technical details: they determine what population the estimate represents and how confidently readers can interpret the comparison. The registry record is useful for understanding the trial's main question and posted result, while its limitations underscore the value of transparent methods and outcome reporting.

17. 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 primary outcome estimate is imprecise: the confidence interval extends from -34.22 to 46.22 min/week. The study enrolled 63, and the outcome results list 32 participants for the comparator and 31 for the intervention. The registry does not explain whether everyone assigned to a group had usable accelerometer data at baseline and 6-months, or whether any outcome measurements were excluded. Missing-data methods and the analysis population are not reported.

The record gives limited detail on intervention implementation. It describes six weekly classes and phone counseling, but not attendance, counseling exposure, or fidelity. It also does not give detailed eligibility criteria or participant characteristics that would help assess how well the study population represents the intended community. The description of single masking does not identify who was masked. Random sequence generation and allocation concealment are not described.

The registry does not report a formal feasibility outcome, an adjusted primary analysis, the original statistical plan, multiplicity handling, interim analyses, or the trial's original sample-size rationale. It lists no posted secondary outcomes. The safety record lists no adverse events in the reported categories, but definitions, collection methods, and observation details are absent; deaths are not reported in the registry record. These limits affect interpretation of the posted results and should not be mistaken for evidence that the unreported procedures or outcomes had a particular value.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Translating a Heart Disease Lifestyle Intervention Into the Community — NCT01647438.
• Registry record last updated 2015-11-02; status last verified 2015-10.
• Results first posted 2015-11-02.
• 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.

21. Record Summary

NCT01647438, titled “Translating a Heart Disease Lifestyle Intervention Into the Community,” is a completed randomized, parallel-group study sponsored by Northwestern University. It enrolled 63 and compared six weekly health education classes with phone counseling against primary care referral and print health education. The study focused on underserved South Asian Americans and aimed to evaluate feasibility and initial effectiveness of a community-based, culturally targeted lifestyle intervention.

The primary outcome was change in accelerometer-measured physical activity from baseline to 6-months, in minutes per week. The registry reports a mean difference of 6.0 min/week, a confidence interval from -34.22 to 46.22, and an unadjusted p-value of 0.77. The interval includes no difference and is broad, so the estimated contrast is not precise. Missing-data procedures, analysis-population definitions, and the original statistical plan are not reported in the registry record.