Using Cognitive Intraindividual Variability to Measure Intervention Effectiveness: Results from the Baltimore Experience Corps Trial

ObjectivesStudies investigating the effectiveness of intervention programs on cognitive ability in older adults are inconsistent; however, these studies generally focus on traditional measures of cognition, and therefore may miss some improvements by not utilizing alternate measures. We evaluate the potential for intraindividual variability in cognitive speed (IIV), a demonstrated sensitive indicator of cognitive functioning, to be used as an index of cognitive plasticity from an intervention. The current study evaluated whether older adults in a school volunteering program showed a reduction in IIV, compared to a low-activity control group over 2 years of exposure.MethodNondemented older adults (n = 336) participated in the Baltimore Experience Corps Trial, an evaluation of a volunteering program conducted at elementary schools designed to increase older adults’ physical, cognitive, and social engagement. Participants completed a cognitive battery that included a Stroop task at baseline and after 12 and 24 months.ResultsTraditional intent-to-treat analyses did not report significant improvements. Participants who complied at the 80th percentile or above showed a significant reduction in IIV at 24 months, with an additional trend of improved IIV with increased compliance to the treatment protocol, both at 12 months, and at 24 months. Men also showed dose-dependent improvements after 12 months.DiscussionThe Experience Corps program resulted in an improvement in cognitive performance as measured by IIV. Analyzing previously collected data with nontraditional measures of cognition, such as IIV, may be a potentially fruitful and cost-effective method for understanding how interventions impact cognition in aging populations.