Cognitive functioning in severe dementia and relationship to need-driven behaviors and functional status

The need-driven behavior model posits that behavior symptoms in dementia result from both background and proximal factors, but empirical support is lacking for many aspects of the model including the relationship among specific cognitive factors and behavior disturbances. This study examined the relationship between cognitive functioning measured by the Severe Impairment Battery (SIB) and behavior disturbances measured by the Behave-AD. Dementia patients (N = 127) at ten nursing homes were evaluated. All were in moderate to severe ranges of cognitive and functional impairment as measured by the MMSE and the Functional Assessment and Staging Tool (FAST). Nine cognitive factors from the SIB, a pain measurement, and several demographic variables were entered into logistic regressions to predict 4 types of need-driven behaviors. Poor scores on the SIB, specifically the language subtest, were significant predictors of Acting Out (odds ratios for 1 standard deviation were 1.61 and 1.98 respectively), and poor scores on the SIB, specifically the visuospatial subtest, were significant predictors of Phobia/Paranoia if a more lenient criteria of p < 0.1 was used (odds ratios for 1 standard deviation were 1.66 and 2.06 respectively). There were no significant predictors of Motor Restlessness or Psychological Distress/Psychotic Symptoms. These results agree with and extend previous findings, suggesting that acting out may be due to the inability to communicate and those with phobias and paranoias are more likely to have poor visuospatial abilities. A final analysis examined the relationship between functional abilities measured by the FAST and cognitive functioning using the SIB total score. There was a positive relationship between functional abilities and cognitive function (rs = -.517). A Kruskal-Wallis One-way ANOVA and post hoc analyses using the Mann-Whitney test revealed the largest decrease in cognitive functioning occurred between the stages in which speech and basic body control was lost (p = .007). These results likely reveal a large decrease in cognitive functioning in this last stage of dementia, as well as the loss of ability to make basic movements necessary to perform many of the SIB items.