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A POPULATION-BASED STUDYOF DOSING AND PERSISTENCE WITH ANTIDEMENTIA MEDICATIONS

Introduction: In animal models of neuro-degenerative disease, neuroinflammation is associated with cytokine-related sickness behaviours, such as apathy, somnolence and malaise. In this study, we aimed to develop and validate a scale to measure cytokine-related sickness behaviour in humans with dementia. Methods: Eighty-five participants with a diagnosis of Alzheimer’s disease (n= 64) or Lewy body dementia (n= 21) were recruited through the memory service in Hampshire, UK; 26 putative sickness behaviours were rated on a 4-point scale by a reliable informant. In phase 1, psychometric analysis, using a discrimination index and categorical principal components analysis, identified items that did not contribute significantly to the total scale variance. In phase 2, the retained items formed a scale that was compared with serum cytokine levels to assess biological construct validity. Serum samples were obtained at the time of scale administration for multiplex cytokine immunoassay. Construct validity was assessed further by principal components analysis. Cronbach’s alpha was calculated to assess internal consistency. A subset of participants (n= 13) underwent a 7-day re-test for test–retest reliability. LrEc approval was granted (LrEc:07/Q1704/78). Results: Phase 1: 16 items had a discrimination index <0.2, or an eigenvalue <0.5. These items were discarded. Phase 2: construct validity for the remaining 10-item scale was demonstrated by significant correlations between the total scale score and levels of serum IFN-γ (Spearman’s r = 0.25, P = 0.019) and IL-4 (Spearman’s r = 0.33, P = 0.002). Categorical principal components analysis revealed two groupings of the 10 scale items consistent with the theoretical construct of sickness behaviour, providing further support for the construct validity of the scale. The 10-item scale had high internal consistency (Cronbach’s alpha = 0.85, 95% CI: 0.81–0.89), and high test–retest reliability (ICC = 0.89, 95% CI: 0.68–0.96). Conclusions:We have presented data to support the validity and reliability of the 10-item.