Dementia is a mental disorder accompanied by global cognitive ability loss including memory, language, and attention in older people with abnormal aging. Due to the lack of disease-modifying treatment at present, early diagnosis becomes paramount in trying to prevent subsequent disability. In practice, a diagnosis is largely based on clinical history and cognitive examination supported by neuropsychological evidence of the pattern of cognitive impairment. However, the onset of cognitive symptoms largely results from neuronal death, which has caused irreversible neurodegenerative damage. To advance the diagnosis and prediction of dementia, there is a need of more sensitive instruments specifically developed for early diagnosis of the risk factors in dementia including effects of risk genes, physical frailty and mild cognitive impairment (MCI), where frailty is an age-related syndrome described as the decreased ability of an organism to respond to stressors. A number of studies have reported that frailty increases the risk of future cognitive decline and dementia. MCI is a nosological entity proposed as an intermediate state between normal aging and dementia.
There is a growing body of evidence suggesting that the cognitive decline in dementia may arise from integrative abnormalities between functionally and/or anatomically related brain regions. Recent advances in brain network analysis shed some lights on the study of large-scale brain system disruptions by using graph theoretical approaches. Particularly, connectivity patterns of dementia were recently reported to fall into dissociated but dispersed brain networks, suggesting that the damage from the disease is transmitted along neuronal pathways rather than by proximity. They inferred that structural and functional connectivity patterns might serve as markers to predict the progression of dementia.
Structural and functional deficits affects by risk genes, frailty, and MCI are under actively studied by means of modern MRI technologies to identify the early markers of dementia. A longitudinal cohort of MCI patients and healthy subjects with different aging range is under studying to clarify the links between genes, structural and functional changes, and cognitive performances. Related effects in brain plasticity through lifespan are studied as well to serve as a standard for further prognosis studies.