A cognitive psychophysiological model to predict functional decline in chronically stressed older adults

The current study evaluated whether psychological distress (composite of depression, anxiety, vital exhaustion), inflammation (C-reactive protein, CRP) and cognitive function (Digit Symbol Test, DST) and their changes mediated the relationship between caregiver status and functional decline. Caregivers for spouses with Alzheimer's disease were compared to demographically-similar non-caregiver spouses at study entry (T1), T2 (1 year later), and T3 (2 years after T1). Caregivers had greater functional impairment, higher distress scores, and poorer DST scores at all points of measurement and also showed functional decline. Non-caregivers did not demonstrate functional decline. Caregivers declined 85% faster than did non-caregivers. Regressions showed that after controlling for functional impairment at T1, illness, medication, and health behavior covariates, psychological distress at T1 and increases in CRP from T1 to T3 mediated the difference in functional decline. Moreover, after DST decline from T1 to T2 was entered in the model, caregiver status, psychological distress and increases in inflammation all showed reductions in their predictive importance. These findings suggest psychological distress and increases in inflammation may help explain why caregivers show greater functional decline than non-caregivers. However, the influences of these psychophysiological variables may be driven in part by cognitive decline prior to functional decline.