Mild cognitive impairment: to treat or not to treat.

Mild cognitive impairment (MCI) refers to memory deficits in excess of normal aging, but not sufficient for the diagnosis of Alzheimer's disease (AD). In general, patients with MCI are not disabled and have no other obvious cognitive deficits other than memory. Many studies have shown that patients with MCI are more likely to progress to AD than age-matched controls. Drug therapy to prevent or delay deterioration in patients with MCI has been tested only very recently. The results of three clinical trials are discussed. One of two trials with donepizil suggests that donepizil may delay onset of AD, but the effect is modest and the side effects are problematic. Galantamine appeared to be associated with excess deaths, and vitamin E was not effective. No medications are currently indicated for the prevention of dementia in patients with MCI.