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

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

doi:10.3389/fnagi.2018.00379

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

Front Aging Neurosci. 2018 Nov 27:10:379. doi: 10.3389/fnagi.2018.00379. eCollection 2018.

Authors

Francis Houde^{1

2}, Sarah Laroche^{1

2}, Veronique Thivierge^{1

2}, Marylie Martel^{1

2}, Marie-Philippe Harvey^{1

2}, Frederique Daigle^{1

2}, Ailin Olivares-Marchant¹, Louis-David Beaulieu^{2

3}, Guillaume Leonard^{1

2}

Affiliations

¹ Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada.
² Research Centre on Aging, CIUSSS de l'Estrie - CHUS, Université de Sherbrooke, Sherbrooke, QC, Canada.
³ Biomechanical and Neurophysiological Research Lab in Neuro-Musculo-Skelettal Rehabilitation, Université du Québec à Chicoutimi, Chicoutimi, QC, Canada.

Abstract

Background: 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. Objectives: 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. Methods: 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_eas), intraclass correlation coefficient (ICC), and smallest detectable change in an individual (SDC_indv) were calculated. Lifestyle, medical and socio-demographic factors were collected using questionnaires. TMS-related outcomes were compared using independent sample t-test based on the presence of chronic health diseases, chronic medication intake, obesity, history of smoking, physical activity levels, gender, and level of education. Results: rMT and cSP measures were the most reliable outcomes, with the lowest SEM_eas and highest ICCs, whereas MEP amplitude-related measures were less reliable. SDC_indv 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. Conclusion: Even though SDC_indv 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.

Keywords: aging; chronic disease; elderly; lifestyle habits; reliability; smallest detectable change; transcranial magnetic stimulation.