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Clinical trials in mild cognitive impairment: lessons for the future


Mild cognitive impairment (MCI) is an operational definition for a cognitive decline in individuals with a greater risk of developing dementia. The amnestic subtype of MCI is of particular interest because these individuals most likely progress to Alzheimer’s disease (AD). Currently hypothesised therapeutic approaches in MCI are mainly based on AD treatment strategies. Long term secondary prevention randomised clinical trials have been completed in amnestic MCI populations, encompassing agents with various mechanisms of action: acetylcholinesterase inhibitors (donepezil, rivastigmine, galantamine), antioxidants (vitamin E), anti-inflammatories (rofecoxib), and nootropics (piracetam). The design of clinical trials in MCI is influenced by study objectives and definition of primary end points: time to clinical diagnosis of dementia, and AD in particular, or symptom progression. As none of the drugs previously shown to have clinical efficacy in AD trials or benefit in everyday practice have met the primary objectives of the respective trials, design of future clinical trials in MCI should be further developed particularly as regards the selection of more homogeneous samples at entry, optimal treatment duration, and multidimensional and reliable outcomes.

  • AChEI, acetylcholinesterase inhibitors
  • AD, Alzheimer’s disease
  • ADAS-Cog, Alzheimer’s Disease Assessment Scale, Cognitive subscale
  • ADCS, Alzheimer Disease Cooperative Study
  • CBCS, Cognitive Battery Composite Score
  • CDR, Clinical Dementia Rating scale
  • CGIC, Clinical Global Impression of Change
  • CIBIC, Clinician’s Interview-Based Impression of Change
  • CIBIC-plus, Clinician’s Interview-Based Impression of Change with caregiver input
  • DSST, Digit Symbol Substitution Test
  • FDA, Food and Drug Administration
  • GDS, Global Deterioration Scale
  • HR, hazards ratio
  • InDDEx, Investigation into the Delay to Diagnosis of AD with Exelon
  • ITT, intention-to-treat
  • MCI, mild cognitive impairment
  • MIS, Memory Impairment Study
  • MMSE, Mini-Mental State Examination
  • NYU, New York University
  • PAS, Preclinical Alzheimer’s Disease scale
  • PP, per protocol
  • RCT, randomised clinical trial
  • WAIS-R, Wechsler Adult Intelligence Scale–Revised
  • WMS-III, Wechsler Memory Scale, Third Edition
  • acetylcholinesterase inhibitors
  • anti-inflammatories
  • antioxidants
  • clinical trials
  • mild cognitive impairment
  • piracetam

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