An Exploration of "Sickness Behavior" in Older Patients with Cancer
Prevailing diagnostic manuals identify major depressive disorder (MDD) as a singular construct, despite its polythetic composition of affective, somatic, and cognitive symptoms. Evidence suggests that inflammation may be an etiological component of depression, although the data to support this hypothesis are inconsistent. In contrast, sickness behavior is a symptom cluster robustly associated with inflammation. Sickness behavior and MDD share several overlapping symptoms; however, the relationship between the two constructs remains unknown. The understanding of sickness behavior in humans, including its association with MDD, would likely be improved by more rigorous study of this construct. The current study sought to prospectively operationalize sickness behavior and develop a measure of its severity in older adults with cancer. This study will accomplish this objective by refining a measure of sickness behavior, the Sickness Behavior Inventory (SBI), which was developed based on psychoneuroimmunology theory and review of the animal literature. A pilot study was conducted to elicit patient feedback on the first iteration of the Sickness Behavior Inventory-Revised (SBI-R). Next, the finalized iteration of the SBI-R was administered to ambulatory older adults with cancer and its psychometric properties were explored, including associations with the Center for Epidemiological Studies Depression Scale and the Neurotoxicity Rating Scale. Finally, the scale was administered to a sample of older breast cancer survivors and healthy controls to examine associations with interlukin-6. Qualitative feedback generally provided support for the coherence and acceptability of the scale. The SBI-R demonstrated reliability and validity in a sample of older adult with cancer. Principal components analysis using varimax rotation supported both a 1- and 3-factor model. A multiple regression model did not predict plasma levels of IL-6 from SBI-R scores, CES-D scores, and body mass index (BMI) in a sample of older breast cancer survivors and healthy controls. The present study provides important information about the construct of sickness behavior and resulted in the first published scale that can be used to systematically measure this construct in humans. Longitudinal research is needed to examine the temporal relationship of inflammation and emergence of symptoms, in addition to the efficacy of interventions.
Tobias, Kristen Gerda, "An Exploration of "Sickness Behavior" in Older Patients with Cancer" (2017). ETD Collection for Fordham University. AAI10621342.