Background: Subjective cognitive impairment (SCI) has been a common, but poorly understood condition, frequently occurring in older persons.
Methods: The past and the emerging literature on SCI and synonymously named conditions is reviewed.
Results: Findings include: (1) There is support from at least one longitudinal study for a long-standing concept of SCI as a pre-mild cognitive impairment (MCI) condition lasting approximately 15years. (2) There are complex relationships between SCI and depression and anxiety. (3) Differences in SCI subjects from age-matched non-SCI persons are being published in terms of cognitive tests, hippocampal gray matter density, hippocampal volumes, cerebral metabolism, and urinary cortisol levels. Psychometric and dementia test score differences between SCI and MCI subjects have long been evident. (4) Predictive electrophysiologic features of subsequent decline in SCI subjects are being published.
Conclusions: Studies of therapeutic agents in SCI treatment and resultant Alzheimer's disease prevention appear to be feasible. These trials are also necessary from a public health perspective.