Practice effects persist over two decades of cognitive testing: Implications for longitudinal research

Abstract

Background Repeated cognitive testing can boost performance due to practice effects (PEs), yet it remains unclear whether PEs persist across multiple follow-ups and long durations. We examined PEs across 17 years from midlife to old age in a nonclinical sample.Method Men (N=1,608) in the Vietnam Era Twin Study of Aging (VETSA) completed neuropsychological batteries comprising 30 measures across 4 waves over 20 years. We leveraged age-matched replacement participants to estimate PEs at each wave. We compared cognitive trajectories and MCI prevalence using unadjusted versus PE-adjusted scores.Result We found significant PEs for multiple tests at all waves, especially in episodic memory and visuospatial domains. Adjusting for PEs resulted in greater cognitive decline and earlier detection of MCI, with up to 20% increased prevalence.Conclusion PEs persist across multiple assessments and decades, even with long testing intervals, underscoring the importance of accounting for PEs in longitudinal studies and clinical trials.Competing Interest StatementAMD is a founder and holds equity in CorTechs Laboratories, Inc., and serves on its Scientific Advisory Board. He is a member of the Scientific Advisory Board of Human Longevity, Inc., and receives funding through research agreements with GE HealthCare and Medtronic. The terms of this arrangement have been reviewed and approved by the University of California San Diego in accordance with its conflict of interest policies. All other authors report no financial interests or potential conflicts of interest.Funding StatementThis work was supported by the National Institute on Aging at the National Institutes of Health (grant numbers R01s AG076838, AG022381, AG050595, AG064955; and K01 AG063805).Author DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesThe details of the IRB/oversight body that provided approval or exemption for the research described are given below:IRB of University of California San Diego and Boston University gave ethical approval for this work.I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).YesI have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.YesInstructions for data access requests are available on the VETSA website (https://psychiatry.ucsd.edu/research/programs-centers/vetsa/researchers.html). Access to data from military induction can be requested from the Vietnam Era Twin Registry (https://www.seattle.eric.research.va.gov/VETR/Investigator_Access.asp).