The Relationship between Cognitive Decline Elderly People and Blood Metal Levels : A Systematic Review

ABSTRACT

OBJECTIVES: There have been several previous studies that the pathology of Alzheimer's disease (AD) might be in part caused or exacerbated by metals. But inconsistent results are often seen in evaluation of levels of metals in Alzheimer's disease patient's blood and control group. So, we conducted a systematic review using a comprehensive search strategy to find out whether there is significant difference between cognitive decline elderly people and normal control group. METHODS: Studies were searched in Pubmed, CINAHL and EMBASE with predefined words according to MeSH and purpose of this study. 996 studies were selected as primary screening, and two reviewers extracted relevant data independent of each other. 172 studies fulfilled the inclusion criteria. 32 studies about aluminum, copper, lead, mercury, cadmium finally selected. The Newcastle-Ottawa Scale (NOS) was used for assessing the quality of studies. To synthesize the results of this study, summarized table was made. RESULTS: In most studies, blood levels of mercury were high in cognitive decline group. But the majority study shows lead was not that different between cognitive decline group and control group. Measurements of other metal levels in whole blood, plasma, serum were inconsistent. However, there are not enough evidences to generalize with just number of studies since the studies have various degrees of validity. CONCLUSION: There is lack of evidences, till now, to use blood levels of metals as diagnostic purpose or predicting prognosis. Further studies which are supplemented limitations of previous studies are needed.