AUTHOR=Houde Francis , Laroche Sarah , Thivierge Veronique , Martel Marylie , Harvey Marie-Philippe , Daigle Frederique , Olivares-Marchant Ailin , Beaulieu Louis-David , Leonard Guillaume 

TITLE=Transcranial Magnetic Stimulation Measures in the Elderly: Reliability, Smallest Detectable Change and the Potential Influence of Lifestyle Habits

JOURNAL=Frontiers in Aging Neuroscience

VOLUME=10

YEAR=2018

URL=https://www.frontiersin.org/journals/aging-neuroscience/articles/10.3389/fnagi.2018.00379

DOI=10.3389/fnagi.2018.00379

ISSN=1663-4365

ABSTRACT=<p><bold>Background:</bold> Transcranial magnetic stimulation (TMS) is a non-invasive technique that can be used to evaluate cortical function and corticospinal pathway in normal and pathological aging. Yet, the metrologic properties of TMS-related measurements is still limited in the aging population.</p><p><bold>Objectives:</bold> The aim of this cross-sectional study was to document the reliability and smallest detectable change of TMS measurements among community-dwelling seniors. A secondary objective was to test if TMS measurements differ between elders based on lifestyle, medical and socio-demographic factors.</p><p><bold>Methods:</bold> Motor evoked potentials (MEPs) elicited by single-pulse TMS were recorded in the first dorsal interosseous (FDI) in 26 elderly individuals (mean age = 70 ± 3.8 years). Resting motor threshold (rMT), MEP amplitudes and contralateral silent period (cSP) were measured on two separate occasions (1-week interval), and the standard error of the measurement (SEM<sub>eas</sub>), intraclass correlation coefficient (ICC), and smallest detectable change in an individual (SDC<sub>indv</sub>) were calculated. Lifestyle, medical and socio-demographic factors were collected using questionnaires. TMS-related outcomes were compared using independent sample <italic>t</italic>-test based on the presence of chronic health diseases, chronic medication intake, obesity, history of smoking, physical activity levels, gender, and level of education.</p><p><bold>Results:</bold> rMT and cSP measures were the most reliable outcomes, with the lowest SEM<sub>eas</sub> and highest ICCs, whereas MEP amplitude-related measures were less reliable. SDC<sub>indv</sub> levels were generally high, even for rMT (7.29 %MSO) and cSP (43.16–50.84 ms) measures. Although not systematically significant, results pointed toward a higher corticospinal excitability in elderly individuals who were regularly active, who had no chronic medical conditions and who did not take any medication.</p><p><bold>Conclusion:</bold> Even though SDC<sub>indv</sub> levels were relatively high, these results show that rMT and cSP are the most reliable outcomes to investigate age-related changes in the corticomotor system and suggest that the influence of factors such as lifestyle habits and medications on TMS measures should be investigated further.</p>