Objectives: To expand the landmark Medical Outcomes Study (MOS) and World Health Organization (WHO) findings on the unique association of symptoms of depression with multiple domains of functioning, health perception, and well-being in consulting populations to the late middle-aged and older community-dwelling population and to contrast this unique association to that of specific chronic medical conditions and sensory and cognitive impairment (collectively denoted as medical conditions (MCs)).
Design: Population-based, cross-sectional health survey.
Setting and participants: A total of 5279 noninstitutionalized late middle-aged and older persons living independently or in residential homes for older people housing in the northern part of The Netherlands.
Measurements: Behavioral: physical functioning, (Independent) Activities of Daily Living ((1)ADL), and role functioning. Subjective: health perception, life satisfaction and well-being. Mixed: discretionary activities and activity level. Two aspects of the association were examined: the unique risk (adjusted difference in mean outcome between those with the condition and those without, expressed in SD units) and the unique contribution (adjusted proportion of variance in outcome accounted for by the condition). The latter takes the prevalence of the condition into account.
Results: Among both individuals with MCs and those without, persons with symptoms of depression did worse on all outcomes than those without. Depressive symptoms were more consequential for subjective and mixed outcomes compared with behavioral outcomes. For all outcomes, none of the unique contributions of MCs exceeded that of depressive symptoms, whereas the unique contribution of depressive symptoms typically outranked those of the MCs. For behavioral outcomes, the unique risks associated with neurological conditions, persistent back problem, arthritis, and stroke exceeded that of depressive symptoms, but risk associated with depressive symptoms exceeded that of nine of 18 MCs, on average. For the mixed and subjective outcomes, none of the unique risks associated with MCs exceeded that of depressive symptoms, but risks of depressive symptoms exceeded those of 16 of the 18 MCs, on average. The effects of depressive symptoms and medical conditions were largely additive although depressive symptoms amplified the effect of some medical conditions on (I)ADL. The pattern of unique risks and contributions was similar across all ages (57-64, 65-74, 75+).
Conclusion: The unique contribution of depressive symptoms in dysfunction, poor health perception, and well-being typically exceeds that of medical conditions because depressive symptoms combine a moderately large unique risk with a rather high prevalence. Results expand the MOS and WHO findings to the community-dwelling late middle-aged and older population and to additional outcomes as well. Results underscore the importance of detection and management of (comorbid) symptoms of depression in older people.