Change in stress and social support as predictors of cognitive decline in older adults with and without depression

Cognitive impairment in late-life depression is a risk factor for multiple adverse outcomes in physical health, functional independence, and mortality (Mehta et al. 2003). Depression in late life may be a prodromal symptom of Alzheimer’s disease and a risk factor for dementia more broadly (Kessing & Nilsson 2003), while cognitive impairment during depression is also associated with persistent deficits (Lee et al. 2007) and dementia (Alexopoulos et al. 1993). Based on community samples, the prevalence of cognitive impairment and comorbid depression doubles at 5-year intervals after the age of 70, and is estimated to be present in 25% of individuals aged 85 and older (Arve et al. 1999). These rates make it important to understand the factors that contribute to acute and persistent cognitive dysfunction in depressed older adults. While studies of depression have examined neurobiological correlates of cognitive dysfunction in depression, less attention has been devoted to the role of psychosocial factors. The association between greater life stress and higher rates of depression has been well established (Kessler 1997; Mazure et al. 2002), and higher perceived stress is associated with incomplete remission of depression (Hybels et al. 2006). Higher levels of perceived stress and stressful life events also have been associated with greater age-related differences on objective measures of episodic memory and executive functions (VonDras et al. 2005). Evidence supports the idea that stress-related coping requires a certain amount of cognitive attention and therefore the presence of major stress reduces the amount of attention one can devote to other information processing tasks (Kahneman 1973; Stawski et al. 2006), which would be exacerbated in later life (Smith 2003), and presumably more so when stress results in a depressive episode. It has also been posed that stress-related hypercortisolemia during depression may have a progressive toxic effect on the hippocampus and associated cognitive functions, which has some support among non-depressed, but is more mixed in studies of late life depression (Lupien et al. 1999; Steffens & Potter 2007). Social support (both perceived and actual) is another psychosocial factor that may contribute to cognitive dysfunction in late life depression. Low levels of perceived social support are associated with longitudinal depression severity (Steffens et al. 2005). Instrumental social support appears to provide a buffer against functional decline in late-life depression (Hays et al. 2001), but the role in cognitive decline is not well studied in this condition. There is evidence in non-depressed elderly, however, that low satisfaction with social support is associated with 5-year decline in episodic memory (Hughes et al. 1988) and that perceived social isolation (i.e., loneliness) is associated with cognitive decline over a 10-year period (Tilvis et al. 2004). Thus, poor social support, or the perception of poor support, may also contribute to cognitive decline among depressed older adults as well. The purpose of this study was to examine the effects of stress and social support on cognition in depressed and non-depressed older adults. We expected that a change in stress from baseline to one-year (and first year of treatment for patients) would predict a change in cognitive performance in follow-up assessments across both the depressed and non-depressed population. In addition, we hypothesized that changes in the level of social support during the first year of the study would affect changes in cognitive ability the following year for the whole sample. We hypothesized an increase in stress or a decrease in social support would predict a decrease in cognitive ability over the following year. We hypothesized that these associations would be significant after controlling for age, sex, years of education and depression status (depressed/non-depressed) at baseline. A secondary objective was to explore which aspects of cognition might be sensitive to the influence of social factors. Overall, the potential clinical importance of this study is that finding specific associations between stress and social support with cognition could highlight potentially modifiable intervention targets to treat depression and prevent cognitive decline.