デュアルタスク対マルチコンポーネント運動：施設入居高齢者における比較 (DT-Fall)

Ageing is a universal biological process. However, the trajectory of physical and cognitive decline varies significantly across individuals based on their lifestyle and environment. Literature consistently demonstrates that older adults residing in long-term care institutions (nursing homes) represent a particularly vulnerable demographic compared to those living in the community. While community-dwelling older adults often maintain a baseline level of physical activity through household chores, social interactions, and recreational tasks, institutionalized older adults frequently face an environment characterized by sedentarism and a lack of autonomy. This environmental physical deprivation in institutional settings leads not only to physical deconditioning (loss of strength, loss of balance, and reduced mobility) but also to a lack of cognitive stimulation. The absence of complex daily challenges means that these individuals rarely engage the neuro-motor pathways required to manage simultaneous tasks. Consequently, institutionalized older adults are at a disproportionately high risk of adverse health outcomes, most notably falls.

Falls are not merely biomechanical events caused by muscle weakness; they are deeply intertwined with psychological factors. Recent systematic reviews highlight fear of falling as a critical health concern that affects a vast majority of institutionalized older adults, regardless of whether they have a history of falling. Fear of falling acts as a psychological barrier that triggers a negative spiral of frailty, specifically, the fear leads to self-imposed activity restriction, which further degrades physical fitness (i.e., strength and balance), thereby paradoxically increasing the actual risk of future falls. Breaking this cycle is imperative. The literature suggests that interventions must address not only the physical capacity to move but also the confidence to move safely. While physical activity is widely recognized as a protective factor, reducing fall risk and promoting independence, the specific type of physical activity that best addresses the psychological aspect of fear of falling remains a subject of investigation.

International guidelines, such as those from the World Health Organization and Cochrane reviews, advocate for multicomponent exercise programs by combining resistance, balance, and aerobic training, as the most effective strategy for fall prevention. These programs, typically prescribed at moderate intensities, have proven effective in improving pure physical parameters like muscle strength and static balance. However, a critical gap exists between clinical improvements and real-world applicability. Standard multicomponent exercise is often performed in controlled environments where the individual focuses exclusively on the motor task (i.e., single tasking). Yet, in daily life, falls rarely occur when an individual is solely focused on walking. Instead, falls predominantly happen during complex, multi-task scenarios, such as walking while talking or carrying objects, navigating obstacles, or processing environmental cues. This discrepancy suggests that traditional multicomponent training may lack ecological validity. It strengthens the muscles but may not sufficiently train the brain to allocate attentional resources efficiently during movement, leaving the older adult vulnerable when distracted.

The Cognitive-Motor Interference theory posits that when older adults with cognitive deficits attempt to perform a motor task and a cognitive task simultaneously, performance in one or both domains deteriorates. This dual-task cost is a strong predictor of falls. Therefore, to effectively reduce fall risk and, crucially, the fear of falling, an intervention must simulate these complex demands. This leads to the hypothesis that dual-task training, the integration of simultaneous cognitive challenges (e.g., verbal fluency, arithmetic calculations, memory recall) into physical exercise, may offer superior benefits to multicomponent training alone. By forcing the central nervous system to manage competing attentional demands, dual-task training aims to improve neuroplasticity and executive function alongside physical conditioning.

The primary aim of this investigation is to determine whether increasing the complexity of the training stimulus (Dual-Task) yields greater benefits than the standard physical stimulus (Multicomponent) in institutionalized older adults. Specifically, this study seeks to understand if adding a cognitive load to a standard exercise protocol is a key ingredient required to significantly reduce fear of falling and improve functional mobility in this specific population. Rather than focusing solely on the volume or intensity of exercise, as emphasized in general guidelines, this research focuses on the specificity of the training type. If dual-task training proves more effective, it suggests that fall prevention strategies in nursing homes should move beyond simple repetitive movements and embrace physical and cognitive training. The findings will support healthcare professionals in tailoring interventions that are not only physically strengthening but also cognitively engaging, ultimately promoting a more robust and confident functional independence among the oldest old.