BACKGROUND: Confounding of depression with somatic illness and anxiety, a 
problem in any age group, may be especially troublesome in frail older persons. 
This paper examined this problem in a factor analytic study of the structure of 
depressive symptomatology, identifying affective and somatic symptom clusters 
and relating those clusters to health and functional variables cross-sectionally 
and prospectively over a 1-year interval.
METHODS: The factor structure of a DSM-IV symptom checklist was examined among 
1,245 elderly long-term care residents. Regression analyses examined the 
association of resulting factors with cognition, functional disability, self- 
and physician-rated health, and pain at baseline and a year later. One-year 
mortality was also examined.
RESULTS: Factor analysis revealed three unique symptom clusters: depressed mood, 
somatic symptoms, and psychic anxiety. Depressed mood and somatic symptoms were 
associated cross-sectionally with all functional health variables, but psychic 
anxiety was associated only with pain. Longitudinally, depressed mood was the 
only independent predictor of decline in cognition, functional ability, 
physician-rated health, and mortality; the last effect, however, did not 
withstand control for baseline health and functioning. Somatic symptoms at 
baseline predicted decrement in self-rated health a year later. Effects varied 
as a function of cognitive status.
CONCLUSIONS: These data suggest that concerns about the confounding role of 
somatic symptoms in the association of depression with physical health are 
unfounded. Although somatic symptoms of depression and anxiety were associated 
with health and functional status cross-sectionally, depressed mood was by far 
the stronger predictor of health declines over time.