Ageing and Health. Spanish Longitudinal Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Ageing and Health. Spanish Longitudinal Study (NCT03343886), a registered phase not stated study. The primary outcome is Heath Status.

2. Clinical Question

3. Trial Design

This is a completed longitudinal cohort study, not a randomized clinical trial. The registry record lists enrollment of 7755 and identifies two cohorts. The 2011 cohort comprised a nationally representative sample of 4753 non-institutionalized adults aged 18 years or older from the Spanish population, with over-sampling of people aged 50 years or older. Recruitment used a multi-stage clustered design. The 2019 cohort brought in 3002 participants from the regions of Madrid and Barcelona between 2019 and 2021.

The baseline data for the 2011 cohort were collected between July 2011 and May 2012 as part of the Collaborative Research on Aging in Europe project. A second wave was conducted between December 2014 and June 2015, and a third wave was conducted in 2018. The registry summary also describes a fourth evaluation in 2022 and a fifth in 2025. It reports that 2528 individuals from the 2011 cohort were re-interviewed in 2014; later participant counts for that cohort are not reported in the registry record.

The 2019 cohort had a second wave in 2023, when 1,116 participants were evaluated, and a final evaluation in 2025, when 844 participants were evaluated. Some participants were interviewed by telephone during the first Coronavirus lockdown in early 2020; the number and selection process are not reported in the registry record. The registry status is completed. The arms are cohort labels, not assigned study treatments, and the cohorts are not a like-for-like control comparison.

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: Respondents unable to undertake the interview because of severe cognitive or physical impairment were administered a shorter version of the questionnaire to a proxy respondent.

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.

Population: At the baseline, 4,753 participants were interviewed (2011 cohort) and in 2019-2021 3,002 participants were brought in (2019 cohort).

6. Primary Endpoint

The registry lists the primary outcome as Heath Status, measured over Baseline.

The registry labels the primary outcome “Heath Status” and describes its construct as health status. It is a health composite total score, reported as a mean with a standard deviation at baseline. The score ranges from 0 to 100, and a score of 0 means lower health status. The registry record does not report the observed mean or standard deviation, nor does it identify an estimated change or contrast as the primary result.

A composite score can bring several measured aspects of health into a single summary. Reporting its mean describes the average score in the analyzed group, while the standard deviation describes how dispersed individual scores are around that average. These summaries answer different questions: an average does not show the full range or shape of individual scores, and a standard deviation is not a confidence interval for the average.

Because the listed timeframe is baseline, this endpoint describes a starting measurement rather than, by itself, a trajectory over follow-up. The study’s broader aim includes examining trajectories and determinants of health, disability and well-being, but the registry record does not report a longitudinal estimate for this primary measure. The scoring details beyond the stated range and direction are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies a continuous primary measure summarized by a mean and standard deviation. It does not report an analysis count, numerical outcome result, confidence interval, hypothesis test, or model specification. The explanations below describe general statistical concepts and should not be read as a claim that a particular method was used for this study.

What does a mean and standard deviation describe?

General: The mean is the arithmetic average of the measured scores in an analyzed group. It offers a concise description of the group’s central level on the score scale. The standard deviation describes the spread of individual scores around that mean. A small spread indicates that scores are relatively clustered around the average; a larger spread indicates greater variability. Neither summary reveals every feature of the score distribution. For example, the same mean and standard deviation can accompany different shapes or concentrations of individual observations.

The health composite is described as ranging from 0 to 100, with 0 meaning lower health status. The registry record does not report the observed mean or standard deviation, so the score’s location and variability in the analyzed participants cannot be assessed from the posted results. The standard deviation should also not be confused with a standard error or a confidence interval: the standard deviation concerns variation among individual scores, while uncertainty around an estimated mean is a separate quantity.

What would a confidence interval mean?

General: A confidence interval expresses uncertainty around an estimate under the assumptions of the method used to construct it. Its width is influenced by the amount of information in the data and by variability. A narrow interval indicates greater precision under those assumptions than a wide interval. The interval does not describe the range containing most individual participant scores, and it does not remove possible bias from selection, measurement, missing data or model assumptions. No confidence interval for the primary measure is reported in the registry record.

Why does the study design matter?

General: In a randomized trial, assignment is designed to make treatment groups comparable, on average, with respect to measured and unmeasured baseline characteristics. This study is described as a cohort study, with no assigned intervention or randomized comparison. Its repeated observations can describe patterns over time, but causal interpretation requires attention to how participants were selected, which characteristics differ, and how outcome and follow-up processes were handled. The registry record does not report an adjusted causal analysis.

The sampling descriptions also distinguish the cohorts. The 2011 cohort used a multi-stage clustered design and over-sampled people aged 50 years or older; such a design may require methods that account for clustering and any sampling weights when estimating population quantities. General: Clustering can make observations within the same sampling unit more alike than observations from different units. Treating clustered observations as fully independent can understate uncertainty. The registry record does not report whether weights, cluster adjustments, or other design-based methods were used. The 2019 cohort was recruited from Madrid and Barcelona, so its stated geographic scope differs from the nationally representative 2011 cohort.

What do the planning assumptions mean?

The record describes planning illustrations based on a fraction of the observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. For non-time-to-event outcomes, such illustrations are expressed as participants per arm; time-to-event illustrations use a total event count. These are planning calculations, not observed results or observed power. The registry record does not report the numerical observed effect used for the illustrations or the study’s own sample-size justification. The two cohorts are not assigned arms, so the equal-allocation assumption in a planning illustration does not make them treatment and control groups.

General: Sample-size planning asks how much information a future or planned comparison might need under specified assumptions. It depends on the effect selected for detection, variability, significance level, power target and design. A planning calculation does not show that a completed study had a particular probability of detecting an effect after its results are known. The registry record does not report an interim analysis plan or the statistical plan used to analyze the study outcomes.

How should uncertainty and multiplicity be considered?

General: When a study examines several outcomes or comparisons, the chance of at least one nominally unusual result can increase if each is tested separately without accounting for multiplicity. Adjustment strategies and a prespecified hierarchy can address different aspects of this issue, but the suitable approach depends on the scientific questions and analysis plan. The registry record lists 15 outcome measures but does not report a multiplicity strategy. It also does not report inferential results for the primary or secondary outcomes, so no claim about statistical significance can be evaluated.

Likewise, longitudinal analysis requires decisions about repeated measurements, participant-level dependence, time points, and incomplete follow-up. General: Measurements from the same person are usually related, so methods that account for this dependence are often considered for repeated-measures data. The registry summary gives wave timing and some follow-up counts, but the statistical methods for repeated observations are not reported in the registry record. Without the analysis details and numerical estimates, the precision and assumptions behind any longitudinal conclusion cannot be assessed.

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("Cohort 2011", "Cohort 2019")
n   <- c(4753, 3002)
m   <- c(66.55, 68.95)
sp  <- c(13.11, 19.87)
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  Cohort 2011  4753  66.550  13.110  66.177  66.923
CARM  Cohort 2019  3002  68.950  19.870  68.239  69.661

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists 15 outcome measures and names secondary outcomes that include depression, suicide behavior, anxiety disorders, diabetes, lung disease and stroke. It does not report a strategy for controlling multiplicity, a hierarchy of outcomes, or the statistical analysis plan. When many outcomes are considered, separate tests can create multiple opportunities for apparently notable results. General: Prespecified priorities and suitable multiplicity methods can help readers distinguish confirmatory questions from exploratory ones. The registry record does not provide enough information to determine how this issue was handled.

Missing-data methods are also not reported in the registry record. The study summary describes repeated waves and gives some counts of participants evaluated: 2528 individuals from the 2011 cohort were re-interviewed in 2014; the 2019 cohort had 1,116 participants evaluated in 2023 and 844 in 2025. These figures describe follow-up participation, but they do not explain why other participants were not evaluated, how missing outcome values were handled, or which participants contributed to each analysis. The number of participants interviewed by telephone during the first Coronavirus lockdown is not reported in the registry record.

The analysis populations are not specified. The record does not report whether analyses used all eligible participants, only those with observed outcome data, or another defined population. It also does not describe imputation, weighting for nonresponse, sensitivity analyses, or methods for accounting for the clustered sampling design. These omissions limit assessment of potential selection and missing-data bias. They do not establish that any particular method was or was not used outside what the registry reports.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: lungs problems (9.0%), stroke (5.9%).

The registry record lists serious adverse-event counts for the two cohorts. For Cohort 2011, 706 were recorded as affected among 4753 at risk; for Cohort 2019, 234 were recorded as affected among 3002 at risk. It also lists other adverse-event counts: 1447 among 4753 at risk for Cohort 2011, and 1474 among 3002 at risk for Cohort 2019. Death counts are listed as 591 and 157, respectively. These figures are counts, not estimates of a treatment effect.

The record lists “Lungs problems” at 9.0% and “Stroke” at 5.9% among the top serious terms. The denominator and observation period for these percentages are not reported in the registry record. Definitions of serious events, whether counts refer to unique people or event episodes, and the relationship of events or deaths to study participation are also not reported. Because this is an observational cohort study with no assigned treatment comparison, the counts alone cannot establish that participation caused an event or death, or support a like-for-like safety comparison between cohorts.

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

The study’s stated purpose is to examine trajectories of health, disability and well-being, and their determinants, in the Spanish ageing population. Its repeated evaluations can provide a framework for describing how measured outcomes vary over time. The primary measure is a baseline health composite score with a defined range and direction. Those design and measurement details clarify the question the study set out to address.

They do not, on their own, establish what the participants’ average baseline score was or how it changed. The registry record does not report a numerical result for the primary measure, an uncertainty interval, or a longitudinal analysis. It therefore does not support a conclusion about the magnitude or precision of change in health status. A score definition is not an outcome finding.

The study also does not test an assigned treatment. The 2011 and 2019 cohorts differ in recruitment timing and geographic scope, and the registry explicitly does not present them as a like-for-like control comparison. Any observed difference between cohort summaries, if reported elsewhere, would need interpretation in light of those design differences and the analysis methods. It would not by itself show that one exposure or intervention caused the difference.

General: Observational longitudinal research can be valuable for describing patterns and generating questions about possible determinants. Causal conclusions require appropriate design and analysis, and remain vulnerable to confounding, selection and measurement limitations. For this record, the essential distinction is between the study’s broad aims and the numerical evidence actually reported: the aims are described, while the primary outcome estimate and statistical analysis are not reported in the registry record.

14. Why This Trial Matters Statistically

This study is statistically notable for its longitudinal scope and its two distinct cohort designs. The 2011 cohort is described as nationally representative of non-institutionalized adults, using multi-stage clustered sampling and over-sampling of people aged 50 years or older. The later cohort recruited participants from Madrid and Barcelona. These features make it important to distinguish population coverage and sampling design from simple cohort size when interpreting estimates.

Repeated evaluations provide the structure for studying trajectories rather than only a single cross-sectional snapshot. The registry summary describes multiple follow-up waves for both cohorts, including a telephone interview for some participants during the first Coronavirus lockdown. Longitudinal data, however, raise questions about repeated-measure dependence, changes in participation, outcome comparability and missing observations. The registry record does not report how those issues were handled statistically.

The record also illustrates why outcome definitions and numerical results must be read separately. It defines the primary health composite score and its direction, but does not report its mean, standard deviation, or analysis. A clearly named endpoint cannot substitute for an estimate and its uncertainty. Similarly, the listing of secondary outcomes and adverse-event counts does not establish that those outcomes were analyzed or that events were caused by participation.

For biostatistical interpretation, the central lesson is that a rich follow-up schedule and a broad set of health questions describe research potential, while conclusions depend on reported analyses, uncertainty, and transparent handling of the sampling and follow-up structure. Here, those analysis details are not reported in 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 registry record does not report the numerical primary endpoint result, its standard deviation, an uncertainty interval, or a statistical analysis. Although the study is described as longitudinal, estimates of change in the primary health measure are not reported. The record lists 15 outcome measures but does not explain how outcomes were prioritized or how multiplicity was handled.

The cohorts differ in recruitment and coverage. The 2011 cohort is described as nationally representative of non-institutionalized adults and uses multi-stage clustered sampling, with over-sampling of people aged 50 years or older. The 2019 cohort was recruited in Madrid and Barcelona. The record does not report whether analyses accounted for clustering or sampling weights, or how cohort differences were addressed. The results should not be read as a randomized comparison.

Follow-up information is incomplete for assessing participant retention and missingness. The registry summary gives selected counts at follow-up, but does not report reasons for non-participation, outcome-specific denominators, missing-data methods, or sensitivity analyses. The number of participants interviewed by telephone during the first Coronavirus lockdown is not reported in the registry record. The scoring procedure and analysis populations are also not reported in the registry record.

Finally, adverse-event definitions, observation periods and attribution are not described. The record’s counts cannot therefore be interpreted as causal safety evidence. These limitations concern what the registry record reports; they do not establish which methods or additional analyses may have been used elsewhere.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Ageing and Health. Spanish Longitudinal Study — NCT03343886.
• Registry record last updated 2026-10-29; status last verified 2024-10.
• Results first posted 2024-10-15.
• 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

NCT03343886 is a completed longitudinal cohort study titled “Ageing and Health. Spanish Longitudinal Study.” Its stated aim is to examine trajectories of health, disability and well-being and their determinants. The record describes a 2011 cohort of 4753 non-institutionalized adults from Spain and a 2019 cohort of 3002 participants from Madrid and Barcelona.

The primary outcome is a baseline health composite total score, summarized as a mean and standard deviation on a scale from 0 to 100, where 0 means lower health status. The registry record does not report the numerical primary result or an analysis. It describes follow-up waves for both cohorts and lists secondary health outcomes and adverse-event counts. The cohorts are not a randomized or like-for-like control comparison.