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Table 4 Individual studies reporting the association between toxic heavy metals and dementia

From: Environmental risk factors for dementia: a systematic review

Study Exposure Sample description N Methodology/design Finding Grade
Fox, 2014 [35] Arsenic Spring Valley Community, Washington, District of Columbia. Spring Valley was built on a chemical weapons lab which caused arsenic to be distributed to the surface soil. Population of Spring Valley 2006 – 2010: 24,762 Comparison of annual average age-adjusted mortality rates (per 100,000) between Spring Valley, Chevy Chase (2004 – 2010) and the US (2007). No measure of arsenic concentration is given for these areas at these times. AD mortality rate in Spring Valley (22.8; CI 20.3 – 25.4) was comparable to the Chevy Chase (22; CI 19 – 25) and US (24.70) rates. No statistically significant difference. B
Dani, 2010 [36] Arsenic Secondary analysis of country-level data. Country-level data. Simulation. Slight increases in arsenic concentration in soil were related to exponential increases in dementia rates at a country level. C
Emard et al., 1994 [37] Lead The IMAGE Project covering the population of Saguenay-Lac-Saint-Jean (SLSJ), Québec. 129 individuals with AD (clinically diagnosed by standard medical services) who were born in SLSJ. Cross-sectional study: principal components analysis. Samples of aquatic sediment were analysed for geochemical variables. AD cases were identified from a registry. 15 individuals with AD were born in areas with lower than average concentration of lead; 49 were born in areas with higher than average concentrations. This difference was statistically significant (P < 0.05). B
  1. AD Alzheimer’s dementia, CI confidence interval, SD standard deviation, SEM standard error of the mean