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 (SEMeas), intraclass correlation coefficient (ICC), and smallest detectable change in an individual (SDCindv) 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 SEMeas and highest ICCs, whereas MEP amplitude-related measures were less reliable. SDCindv 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 SDCindv 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.
Highlights
Normal aging is characterized by a decline in cognitive and sensorimotor functions, paralleled by progressive changes in the central nervous system (CNS) structure, function, and biochemistry
Most chronic illnesses consisted in arthritis/osteoarthritis and vascular risk factors, conditions which are highly prevalent in the elderly population (Espeland et al, 2017)
The use of Transcranial magnetic stimulation (TMS) measures could provide meaningful information on age-related changes in the motor cortex and might even be able to predict the development of sensorimotor disorders or functional limitations in the future
Summary
Normal aging is characterized by a decline in cognitive and sensorimotor functions, paralleled by progressive changes in the CNS structure, function, and biochemistry (for reviews cf. Seidler et al, 2010; Turner and Spreng, 2012; Rossini et al, 2015). The neurophysiological mechanisms underpinning age-related decline in motor performance can be probed by TMS (reviewed in Levin et al, 2014). TMS is a safe and non-invasive method to assess the excitability and integrity of the motor cortex and the corticospinal tract, as well as intracortical and interhemispheric inhibitory/excitatory mechanisms involved in motor control (Kobayashi and Pascual-Leone, 2003; Reis et al, 2008; Rossi et al, 2009; Rossini et al, 2015). When the coil is placed over the primary motor cortex (M1) on the subject’s scalp, the magnetic pulse trans-synaptically depolarizes pyramidal neurons in M1 via cortical horizontal connections. 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. The metrologic properties of TMS-related measurements is still limited in the aging population
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