Similarities, differences and overlaps between frailty and Parkinson's disease.

Parkinson's disease is a neurodegenerative disorder clinically characterized by bradykinesia, rest tremor, rigidity, and postural and gait disturbances, which are frequently observed in older people. It also shows non-motor symptoms, such as depression, anxiety, cognitive impairment and dementia. The number of patients is gradually increasing worldwide. Aging is a risk factor for the onset of Parkinson's disease, and various physiological effects of aging influence its progression. Frailty is a geriatric syndrome in which the reversible and vulnerable status between robustness and disability is affected by various physiological stressors with aging. Frailty consists of physical, psychological and social aspects. Furthermore, sarcopenia, a syndrome characterized by the loss of muscle mass, strength and function, is also significantly associated with frailty. To maintain the quality of life of older people, frailty, including sarcopenia, should be quickly and appropriately managed. Polypharmacy is an important factor causing the progression of frailty in geriatric syndrome. Although Parkinson's disease and frailty have similar symptoms, and are considered to affect each other, the clinical features and mechanisms of both largely remain unclear. Nevertheless, little literature on the relationship between frailty and Parkinson's disease is currently available. This narrative review aims to clarify the relationships between Parkinson's disease and frailty, not only on the physical, but also on the mental, cognitive, and social aspects and issues regarding polypharmacy in Parkinson's disease explored by previous studies. Geriatr Gerontol Int 2022; 22: 259-270.