Researchers from the University of New South Wales in Australia systematically reviewed results from clinical trials that examined whether cognitive exercises had any inoculative effect against the onset of dementia.

Fifty-four studies were reviewed to identify randomized controlled trials that tested the effect of a discrete cognitive exercise program on neuropsychological performance over time in healthy older adults.

Seven randomized, controlled trials (RCT’s) met the criteria. Pre- and post scores were  analyzed.  A strong effect size was observed for cognitive exercise  interventions, as compared with wait-and-see control conditions (WMD = 1.07, CI: 0.32-1.83, z = 2.78, N = 7, p = 0.006, N = 3,194).
 
RCTs with a follow-up of greater than 2 years did not appear to produce any lower effect sizes than less extended follow-up.  (The quality of reporting of trials was in general low.)
 
The review concludes that cognitive exercise training in healthy older individuals produces strong and persistent protective effects on neuropsychological performance over time. Transfer of these effects to dementia-relevant domains, such as general cognition and daily functioning, has also been reported in some studies. However, cognitive exercise has yet to be shown to prevent incident dementia in an appropriately designed trial, and this is now an international priority.

Citation:  Valenzuela M, Sachdev P. Can cognitive exercise prevent the onset of dementia? Systematic review of randomized clinical trials with longitudinal follow-up. American Journal of Geriatriaric Psychiatry. 2009 Mar;17 (3): pages 179-87. [email protected]