Blood zinc levels and cognitive and functional evaluation in non-demented older patients

Abstract

A complete battery of geriatric and psychometric tests was used to determine whether plasma-borne zinc (Zn), a key ion in neuroplasticity, can be associated with the severity of functional, psychological and cognitive impairment in non-demented older individuals. There was a significant positive correlation between plasma Zn levels and the concentration subcategory measured with the Mini-Mental State Examination (MMSE) test (p < 0.001), but not the total MMSE score, and the levels were significantly reduced in polymedicated patients (defined as concurrent administration of >5 drugs). No correlations were found between plasma Zn levels and depressive symptoms measured with the Yesavage scale for geriatric depression or the Barthel Index - a measurement of the ability of individuals to perform the activities of daily living. Depressive symptoms were associated with poor sleep quality and polymedication (p < 0.001 and p < 0.05, respectively). Our results suggest that peripheral Zn concentration may play a role in the physiopathology of some domain of cognitive function. No correlation to depressive symptoms in the geriatric population under antidepressant drug treatment was observed. However, further studies are needed to understand the relationship between circulating Zn and concentration deficits in order to determine whether Zn represents a candidate early biomarker for cognitive impairment.

Keywords: Barthel Index; Depression; Mini-Mental State Examination; Sleep; Zinc.