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@ARTICLE{Fromm:280028,
      author       = {Fromm, Anna Elisabeth and Trujillo-Llano, Catalina and
                      Grittner, Ulrike and Meinzer, Marcus and Flöel, Agnes and
                      Antonenko, Daria},
      title        = {{I}ncreased variability in response to transcranial direct
                      current stimulation in healthy older compared to young
                      adults: {A} systematic review and meta-analysis.},
      journal      = {Brain stimulation},
      volume       = {18},
      number       = {4},
      issn         = {1935-861X},
      address      = {New York, NY [u.a.]},
      publisher    = {Elsevier},
      reportid     = {DZNE-2025-00872},
      pages        = {1257 - 1265},
      year         = {2025},
      abstract     = {Healthy aging is associated with a decline in cognitive and
                      motor functions, affecting daily activities and quality of
                      life. Combining transcranial direct current stimulation
                      (tDCS) with behavioral training may be a promising
                      intervention against this decline. However, individual
                      response variability may obscure group-level effects and
                      mislead conclusions about tDCS efficacy. Quantifying this
                      variability is crucial for accurately assessing stimulation
                      effects and understanding individual response factors, like
                      age. Yet, no study has quantitatively compared tDCS
                      variability across age groups. This systematic review and
                      meta-analysis examine age-related variability in cognitive
                      and motor responses to tDCS.Following PRISMA guidelines, we
                      searched PubMed and Cochrane for studies directly comparing
                      young and healthy older adults under similar experimental
                      conditions. Across 19 studies comprising 390 older adults
                      (mean ± SD age: 67 ± 5 years) and 384 young adults (mean
                      ± SD age: 24 ± 3 years) receiving transcranial direct
                      current (tDCS), we quantified behavioral variability using
                      the log-transformed coefficient of variation ratio
                      (lnCVR).Results revealed substantially higher response
                      variability in healthy older compared to young adults during
                      active tES (21 $\%,$ lnCVRactive = -0.24 [-0.43, -0.04], p =
                      0.02), but not during sham conditions (lnCVRsham = -0.18
                      [-0.42, 0.05], p = 0.13).These findings provide the first
                      quantitative evidence that advanced age increases behavioral
                      tDCS response variability, highlighting the need to develop
                      personalized tDCS approaches to optimize their efficacy in
                      older populations.},
      keywords     = {Aging (Other) / Meta-analysis (Other) / Stimulation effect
                      (Other) / Transcranial direct current stimulation (tDCS)
                      (Other) / Transcranial electrical stimulation (tES) (Other)
                      / Variability (Other)},
      cin          = {AG Flöel},
      ddc          = {610},
      cid          = {I:(DE-2719)5000081},
      pnm          = {353 - Clinical and Health Care Research (POF4-353)},
      pid          = {G:(DE-HGF)POF4-353},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:40633904},
      doi          = {10.1016/j.brs.2025.06.005},
      url          = {https://pub.dzne.de/record/280028},
}