Interactive Effect of Depression and Cognitive Impairment on Olfactory Identification in Elderly People.

Olfactory identification (OI) deficits have been regarded as an indicator of cognitive impairment in the elderly, but few studies have analyzed the mixed effect of depression on OI. Since depression is common in the elderly and strongly associated with OI, we aimed to explore whether the comorbidity of depression and cognitive impairment may be associated with worse outcomes. In total, 153 elderly patients with depression and 154 normal elderly were recruited. Subjects underwent assessments of depression, cognitive function, and OI. Information on the factors that may affect OI performance was collected (age, sex, smoking history, diabetes, etc.). Correlation analysis showed that several factors had a significant influence on OI performance in the elderly, including severity of depression, cognitive scores, age, sex, and years of education (p < 0.05). Among the different cognitive domains, OI was positively associated with global cognition, memory, language, executive function, and attention performance (p < 0.05). The multiple linear regression analysis indicated that memory scores, age, HAMD scores, and sex were the most relevant factors to OI scores across all elderly participants. The factorial analysis suggested that elderly with comorbidity of depression and cognitive impairment (memory deficits or language deficits) had worse OI impairment, and there was an interactive effect of depression and memory deficits on OI in elderly people. The present study suggested that the coexistence of depressive symptoms and cognitive impairment was associated with worse OI in the elderly. Studies exploring the association between OI and cognitive function should include an assessment of depression and adjust the interactive effects of depression.