WiSER: Robust and scalable estimation and inference of within-subject variances from intensive longitudinal data

Christopher A. German, Janet S. Sinsheimer, Jin Zhou, Hua Zhou

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


The availability of vast amounts of longitudinal data from electronic health records (EHRs) and personal wearable devices opens the door to numerous new research questions. In many studies, individual variability of a longitudinal outcome is as important as the mean. Blood pressure fluctuations, glycemic variations, and mood swings are prime examples where it is critical to identify factors that affect the within-individual variability. We propose a scalable method, within-subject variance estimator by robust regression (WiSER), for the estimation and inference of the effects of both time-varying and time-invariant predictors on within-subject variance. It is robust against the misspecification of the conditional distribution of responses or the distribution of random effects. It shows similar performance as the correctly specified likelihood methods but is 103 ∼ 105 times faster. The estimation algorithm scales linearly in the total number of observations, making it applicable to massive longitudinal data sets. The effectiveness of WiSER is evaluated in extensive simulation studies. Its broad applicability is illustrated using the accelerometry data from the Women's Health Study and a clinical trial for longitudinal diabetes care.

Original languageEnglish (US)
Pages (from-to)1313-1327
Number of pages15
Issue number4
StatePublished - Dec 2022


  • blood pressure variability
  • electronic health record (EHR)
  • glycemic variation
  • intraindividual variability
  • mHealth
  • method of moments

ASJC Scopus subject areas

  • Statistics and Probability
  • General Biochemistry, Genetics and Molecular Biology
  • General Immunology and Microbiology
  • General Agricultural and Biological Sciences
  • Applied Mathematics


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