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

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