Dementia, predominantly a neurodegenerative condition associated with aging, is characterized by progressive cognitive decline and significantly increases the risk of head trauma. In Japan, where population aging is rapidly advancing, the number of individuals with dementia and cognitive impairment is on the rise, and accordingly, the incidence of head trauma in this population is estimated to be increasing. The impact of dementia and cognitive impairment on head trauma can be best understood from three perspectives: injury risk, intracranial hemorrhage risk, and aggravation risk. Patients with dementia or cognitive impairment are at increased risk of head trauma due to higher susceptibility to falls and traffic accidents. Anatomically, brain atrophy leads to enlargement of the subdural space, which predisposes patients to intracranial hemorrhage following head injury. Furthermore, in addition to this anatomical vulnerability, decreased intracranial compliance may lead to rapid and severe deterioration when pressure buffering effect is lost by bleeding or swelling. Currently, no treatment guidelines specific to head trauma in patients with dementia or cognitive impairment have been established. Preventive interventions, such as fall prevention strategies, remain the primary approach. In the future, the development of multidisciplinary treatment protocols tailored to this population is urgently needed.