Physical social isolation is an increasingly evident challenge in modern society and can have significant effects on mental and cognitive health. Reduced in-person social interactions and limited participation in community activities restrict cognitive stimulation, affect emotional balance, and may contribute to cognitive decline. These changes increase the vulnerability of older adults to neurodegenerative disorders, including Alzheimer’s disease. This paper employs an analysis of the scientific literature, selecting and synthesizing relevant studies published between 2015 and 2025 on the effects of physical social isolation on the cognitive health of adults and older adults. The analysis emphasizes social, psychological, and biological mechanisms, highlighting common findings across research and identifying factors that can be addressed through preventive interventions and cognitive stimulation strategies. At the biological level, the absence of regular face-to-face interactions can disrupt the stress response and negatively affect brain structures involved in memory and learning. Psychologically, feelings of loneliness and depression accelerate cognitive deterioration. From a social perspective, the lack of support networks and opportunities for intellectual engagement reduces cognitive resilience and increases exposure to additional risk factors. The findings highlight implications for public health and underscore the need for integrated strategies that promote social inclusion, community participation, and cognitive stimulation as effective and sustainable preventive measures. This approach emphasizes that physical social isolation should be recognized not only as an individual issue but as a significant and complex risk factor requiring coordinated policies, programs, and interventions to support the cognitive well-being of older adults.