Role of MT1A Polymorphism and Environmental Mercury Exposure on the Montreal Cognitive Assessment (MoCA).

PURPOSE: Many age-related structural and functional changes in the brain have important consequences. Long-term exposure to mercury and the impact of functional polymorphisms of metal-regulating proteins such as metallothioneins (MTs) can result in neurological-neurobehavioral effects in elderly individuals. Therefore, the aims of this study are to examine the associations between biomarkers of mercury exposure and cognitive impairment and to investigate the effect of the rs8052394 single nucleotide polymorphism (SNP) of the potential modifier gene MT1A on different domains of the Montreal Cognitive Assessment (MoCA). MATERIALS AND METHODS: We studied 436 participants aged ≥55 years from the Electricity Generating Authority of Thailand study. They underwent a physical examination, an extensive cognitive assessment with the MoCA (cutoff <26 points), and a biochemical analysis related to diabetes and dyslipidemia. The blood mercury level was determined by inductively coupled plasma mass spectrometry. Genotyping of the MT1A rs8052394 SNP was performed by the restriction fragmentation length polymorphism method. RESULTS: The mean age of the study population was 58.8±3.01 years, and most had ≥12 years of education (75.7%). The primary study finding was that the prevalence of mild cognitive impairment (MCI) in older Thai adults was 39.7%. The frequency distributions of the G allele of the rs8052394 SNP of the MT1A gene were significantly associated with the total and sub-domain MoCA scores. The prevalence of MCI was significantly associated with increased age, hypertriglyceridemia, hyperhomocysteinemia, the third tertile of blood mercury concentration, and the rs8052394 variant genotype of MT1A (P values for all odds ratios <0.05). CONCLUSION: These findings suggested that neurocognitive effects associate with mercury exposure and genetic susceptibility in toxicokinetics. Public health strategies can be used to implement as a comprehensive action plan to educate vulnerable populations on how to reduce mercury exposure. Concurrently, impact of such genetic predisposition requires replication for identifying and protecting susceptible individuals from mercury toxicity.

Modified Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) as a screening test for dementia for Thai elderly.

A potential test for early detection of dementia in the elderly is the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE), which is based on information from the informant for the elderly about the changes of the elderly in everyday cognitive functioning associated with dementia. The present study aimed to modify and assess the reliability and validity of the modified IQCODE consisting of 32 items. The study consisted of two methods of assessing dementia: DSMIV diagnosis carried out by clinicians, and informants responding to the IQCODE. The subjects were 200 pairs of elderly subjects and their informants who visited the Geriatric Clinic, Ramathibodi Hospital. The optimal cutoff score on the modified IQCODE was 3.42, with 90% sensitivity and 95% specificity. The positive predictive values, negative predictive values, and accuracy were 0.94, 0.90, and 0.92, respectively. The IQCODE items had high internal consistency. The IQCODE associated with the elderly person's age, but not with their gender and educational level; nor were they associated with the demographic characteristics of the informant. Therefore, the IQCODE could be used as an alternative screening test for dementia in Thailand with acceptable sensitivity and specificity. This tool may be useful for dementia screening in the community and the geriatric clinic for early detection of disease.

Undiagnosed dementia and value of serial cognitive impairment screening in developing countries: a population-based study.

BACKGROUND: We conducted a population-based prospective study in 420 older persons to examine the prevalence of undiagnosed dementia and validity of the Chula Mental Test (CMT) as well as value of serial administration of the CMT and its score evolution over 2 years. METHODS: The CMT score was obtained in 1997 and 1999 surveys. In 1999, all participants were evaluated by a geriatrician to make diagnoses of dementia according to the 4th edn of the Diagnostic and Statistical Manual criteria. Information on previous diagnosis of dementia by physicians was collected. Validity of the CMT was determined by the receiver-operator curve. The pattern of cognitive evolution over 2 years was analyzed. RESULTS: Of 420 subjects, 23 had dementia, of which 22 (95.6%) were undiagnosed. The prevalence (95% confidence interval) of dementia and undiagnosed dementia were 5.5% (3.3-7.7%) and 5.3% (4.1-6.3%), respectively. With original cut-off (15/14) of the CMT, the sensitivity and specificity were 0.74 and 0.86, respectively. The best cut-off found in this study was 16/15 which provided better sensitivity (0.91) but worse specificity (0.76) than those of the original cut-off. Pattern of cognitive evolution was heterogeneous. The heterogeneous change was substantial in subjects with mild low CMT score. Cognitive evolution pattern showed that serial administration of the CMT could reduce workload of primary care physicians and might be useful in a screening protocol. CONCLUSION: The prevalence of undiagnosed dementia in community-dwelling Thai older persons was high. The CMT was valid for use in a community. Heterogeneous evolution of cognitive function and value of serial cognitive impairment screening was found.