Serum Level Of Trace Metals In The Mild Cognitive Impairment, Alzheimer's Disease And Normal Control Groups

Abstract

Introduction: As population aging, dementia has one of the highest burdens of disease among the elderly. Alzheimer`s disease (AD) is the most common type of dementia. Previous studies indicated AD is associated with trace metal toxicity. The etiologic roles of metals, however, are still questionable especially about the progression of mild cognitive impairment (MCI) to AD. Therefore we investigated the association between the metals and the risk of MCI and AD. Methods: Among 4 cohorts, 50 MCI and AD cases were recruited from a hospital patient cohort and compared with 155 normal controls from other cohorts. Four trace metals, aluminum (Al), lead (Pb), mercury (Hg), and manganese (Mn) were investigated. Logistic analysis was used to estimate odds ratios (ORs) for cases including MCI and AD. Since MCI and AD were analyzed as ordinal variables, generalized logit and cumulative logit model were used. Results: The geometric means (± interquartile ranges) of metals (Al, Hg, Mn, Pb) for controls (9.7 ± 4.0, 2.3 ± 2.4, 9.8 ± 3.6, 2.3 ± 1.2 ㎍/L) were higher than the cases (8.3 ± 3.3, 2.1 ± 1.7, 9.2 ± 4.0, 1.8 ± 0.9 ㎍/L). In all 3 models, after adjusting age, sex, BMI, smoking and education level, none of the ORs were statistically significant. Though, the interaction between smoking and Hg was significant in some model. Stratified by the smoking status, Hg was 1.16 times higher (95% CI 1.03-1.31) in non-smokers (NS) and 0.12 times lower (0.02-0.77) in smokers. In the generalized logit model, however, OR for AD was 1.24 (p = 0.074) in NS. Smokers had a 4.96 (p = 0.046) higher chance of suffering from MCI. In the multinomial cumulative logit model, although proportional odds assumption was not satisfied, due to the small size, the ORs was still significant for both NS and smokers; 1.12 (95% CI 1.001-1.25) and 0.22, (95% CI 0.07-0.68) respectively. Conclusion: Serum Hg level, with an interaction with smoking status, accounts for the progression from normal to MCI significantly.