Paper 21: Using isotemporal substitution to predict the effects of changing physical behaviour on older adults’ cardio-metabolic profiles

Author

Lee Jones - Senior Biostatistician - Statistical Review

Published

March 15, 2026

Reference

Ryan DJ, Wullems JA, Stebbings GK, Morse CI, Stewart CE, Onambele-Pearson GL (2019) Using isotemporal substitution to predict the effects of changing physical behaviour on older adults’ cardio-metabolic profiles. PLoS ONE 14 (10): e0224223. https://doi.org/10.1371/journal.pone.0224223

Ryan, Declan, Wullems, Jorgen Antonin and Onambélé-Pearson, Gladys (2019) Using isotemporal substitution to predict the effects of changing physical behaviour on older adults’ cardio-metabolic profiles. [Dataset] https://doi.org/10.23634/MMUDR.00623717

Disclosure

This reproducibility project was conducted to the best of our ability, with careful attention to statistical methods and assumptions. The research team comprises four senior biostatisticians (three of whom are accredited), with 20 to 30 years of experience in statistical modelling and analysis of healthcare data. While statistical assumptions play a crucial role in analysis, their evaluation is inherently subjective, and contextual knowledge can influence judgements about the importance of assumption violations. Differences in interpretation may arise among statisticians and researchers, leading to reasonable disagreements about methodological choices.

Our approach aimed to reproduce published analyses as faithfully as possible, using the details provided in the original papers. We acknowledge that other statisticians may have differing success in reproducing results due to variations in data handling and implicit methodological choices not fully described in publications. However, we maintain that research articles should contain sufficient detail for any qualified statistician to reproduce the analyses independently.

Methods used in our reproducibility analyses

There were two parts to our study. First, 100 articles published in PLOS ONE were randomly selected from the health domain and sent for post-publication peer review by statisticians. Of these, 95 included linear regression analyses and were therefore assessed for reporting quality. The statisticians evaluated what was reported, including regression coefficients, 95% confidence intervals, and p-values, as well as whether model assumptions were described and how those assumptions were evaluated. This report provides a brief summary of the initial statistical review.

The second part of the study involved reproducing linear regression analyses for papers with available data to assess both computational and inferential reproducibility. All papers were initially assessed for data availability and the statistical software used. From those with accessible data, the first 20 papers (from the original random sample) were evaluated for computational reproducibility. Within each paper, individual linear regression models were identified and assigned a unique number. A maximum of three models per paper were selected for assessment. When more than three models were reported, priority was given to the final model or the primary models of interest as identified by the authors; any remaining models were selected at random.

To assess computational reproducibility, differences between the original and reproduced results were evaluated using absolute discrepancies and rounding error thresholds, tailored to the number of decimal places reported in each paper. Results for each reported statistic, e.g., regression coefficient, were categorised as Reproduced, Incorrect Rounding, or Not Reproduced, depending on how closely they matched the original values. Each paper was then classified as Reproduced, Mostly Reproduced, Partially Reproduced, or Not Reproduced. The mostly reproduced category included cases with minor rounding or typographical errors, whereas partially reproduced indicated substantial errors were observed, but some results were reproduced.

For models deemed at least partially computationally reproducible, inferential reproducibility was further assessed by examining whether statistical assumptions were met and by conducting sensitivity analyses, including bootstrapping where appropriate. We examined changes in standardized regression coefficients, which reflect the change in the outcome (in standard deviation units) for a one standard deviation increase in the predictor. Meaningful differences were defined as a relative change of 10% or more, or absolute differences of 0.1 (moderate) and 0.2 (substantial). When non-linear relationships were identified, inferential reproducibility was assessed by comparing model fit measures, including R², Akaike Information Criterion (AIC), and Bayesian Information Criterion (BIC). When the Gaussian distribution was not appropriate for the dependent variable, alternative distributions were considered, and model fit was evaluated using AIC and BIC.

Summary from statistical review

This study examined the effects of replacing one hour of sedentary behaviour with alternative active behaviours on seven cardiometabolic parameters. The article was difficult to interpret due to extensive use of acronyms and technical terminology. Seven cardiometabolic outcomes were analysed, with separate models fitted for each of five replacement behaviours, and each model estimated both with and without covariate adjustment.

The authors did not address multiple-comparison issues or the interrelated nature of the statistical tests. Although collinearity was acknowledged, it was assessed using pairwise correlation coefficients rather than variance inflation factors. Several regression results reported in the Supporting Information exhibited large standard errors, suggesting instability in parameter estimates and potentially consistent with multicollinearity. Only statistically significant findings were presented in the main text, which may place disproportionate emphasis on positive results; however, all fitted models were made available in the Supporting Information.

The modelling strategy does not appear to follow a recognised or prespecified analytic framework and relied largely on author judgement for variable selection. Given the modest sample size of 93 participants, this approach may increase the risk of model overfitting. A key strength of the study is its comprehensive examination of how cardiometabolic profiles may vary with changes in physical behaviour, and its attempt to relate these changes to clinically relevant cardiometabolic outcomes.

Data availability and software used

The authors suggest that the “data underlying the study is available”; however, the downloadable Excel file only contained analyses and not the underlying dataset. SPSS was used for analyses of linear regression models.

Regression sample

The data to reproduce the linear regression models were not available.

Computational reproducibility results

The data to reproduce the linear regression models were not available.

Inferential reproducibility results

The data to reproduce the linear regression models were not available.