A major issue of scientific and clinical importance to understanding dementia is determining in what ways depression affects cognitive and noncognitive symptoms. Family caregivers report that the noncognitive symptoms of dementia (e.g., apathy, agitation) have greater impact on the family unit's day-to-day life than do the cognitive symptoms of dementia (Riley & Snowden, 1999). Of concern, then, is how depressive syndromes affect the behaviors of the person with dementia and whether depression should be an area of intense intervention, not only to remove the depressive symptoms but to forestall excess disabilities in persons with dementia. One conceptual framework to use in assessing these issues is the activity limitation framework.
The activity limitation framework was developed from research data that focused on medically ill elders (Williamson, 1992; Williamson & Schulz, 1995). Physical illness, pain, functional abilities, and depression were investigated cross-sectionally and longitudinally. The authors reported that it was only the changes in physical health such as pain that affected functional skills related to depression. Another way of stating this finding is to view activity limitation as a mediator of pain and depression. Thus, in extrapolating this to dementia, it is to the extent that functional skills are affected that depressive syndromes emerge and remain stable. This framework has some empirical support for it, both in general geriatric medical studies and in studies of demented elders.
Nanna, Lichtenberg, Abuda-Bella, and Barth (1997) reported on 423 cognitively impaired (56%) and intact (44%) medical rehabilitation patients. Both cognition and depression were independent predictors of functional recovery beyond initial level of function and demographic variables. Those with depression had less functional recovery than those without depression. A more recent study focused on the specific relationship between depression and functional abilities in primary care elders.
Stewart, Prince, Richards, Brayne, and Mann (2001) compared the relationships between depression and disablement and depression and cardiovascular risk factors in a sample of 287 primary care Caribbean-born elders. Nineteen percent of the sample was classified as depressed, 58% had hypertension, 29% had diabetes, and 16% had a Mini-Mental State Examination (MMSE) score of less than 20. Basic and advanced activities of daily living as well as mobility were also measured. The authors reported a strong association between depression and disablement but no association between CVRFs and depression. The authors used only measures of individual CVRFs and no cumulative vascular burden measure. Mast (2002) and Yochim and Lichtenberg (2002) have demonstrated that CVRFs and depression may be related only when there is cumulative vascular burden. Nevertheless, the results of the study supported the activity limitation framework.
Hargrave, Reed, and Mungas (2000) investigated depressive syndromes and functional disability in dementia among AD (n = 582), VaD (n = 48), and mixed AD and VaD patients (n = 61). Several interesting findings emerged from these data. First, depression was related to both demographic factors and type of dementia. Major and minor depression were more common in those with less education, and major but not minor depression was more common in those with VaD than with AD. In relation to the activity limitation framework, depression was significantly related to both cognition and functional abilities and was significantly more related to functional abilities than to cognition. These data provided support for the activity limitation framework in demented elders.
Espiritu et al. (2001) used slightly differing methodology but reported findings similar to the Hargrave study. The group investigated caregiver reports of functional abilities using self-reported depression and the MMSE in more than 200 demented elders. Whereas the Hargrave study used rate-based depressive determination, self-report depression was significantly related to ADL skills in the Espiritu sample beyond the effects of demographic and cognitive factors. Thus, the significant relationship between self-reported depression with caregiver reports of function provided further support for the activity limitation framework.
Starkstein et al. (1997) reported on a prospective study of depression in AD. These researchers categorized 62 patients as either not depressed, having minor depression, or having major depression at baseline and reex-amined the groups at two-year follow-up. Nineteen percent of the sample had major depression at baseline, and half of this group remained depressed at follow-up regardless of whether they underwent antidepressant treatment. Thirty-four percent of the sample had minor depression at baseline, and at follow-up only 28% remained in the minor depressed group. Twenty-one percent of the nondepressed group at baseline had depression on follow-up. Both cognition and functional abilities declined at the same rate for each group regardless of depression status. In this sample, no support was found for the activity limitation framework, although the authors did not investigate the depression groups separately to see who remained depressed versus those whose depression remitted.
The presence and course of depression in long-term care residents is another important area of research and clinical practice. Janzig, Teunisse, Bouwens, Hof, and Zitman (2000) investigated depression in 91 demented and 110 nondemented long-term care residents at baseline and at 6- and 12-month follow-up. At baseline, 32% of dementia patients had major (12%) or minor (20%) depression, and 50% of nondemented residents had major (11%) or minor (39%) depression. Functional abilities and depression severity at baseline, and not dementia status, predicted depression persistence, thus supporting the activity limitation framework. These rates of depression in long-term care match those of many other researchers (Gerety et al., 1994; Lichtenberg, 1994).
Menon et al. (2001) investigated other noncognitive symptoms that are related to the presence of depression. They investigated 1,101 long-term care residents with dementia in a stratified random sample of 59 long-term care facilities. In those with a dementia diagnosis, verbal and physical aggression were more frequent. Twenty-one percent of the demented group was depressed and, as compared to the nondepressed dementia patients, the depressive had significantly more ADL limitations and psychiatric symptoms than did the nondepressive group. Specifically, those patients who were moderate to severely demented and had depression were more likely to be physically and verbally aggressive.
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