Association between arsenic exposure and the risk of Alzheimer's disease: A cohort study in Sweden

BackgroundEvidence on whether arsenic in groundwater is associated with the risk of Alzheimer's disease (AD) is limited.ObjectiveTo investigate the association between long-term exposure to different levels of arsenic and the risk of AD.MethodsWe conducted a population-based cohort study included individuals born in Sweden during 1932-1950 (n = 1,549,700), with follow-up from 1970 until 2016. We classified study individuals by groundwater arsenic levels reported by the Geological Survey of Sweden and identified AD diagnoses through the Swedish National Patient Register and Cause of Death Register. The association between arsenic exposure and AD risk was evaluated using Cox models.ResultsAmong the 1,549,700 individuals [761,055 female (49.1%); mean (SD) age at baseline: 26.5 (5.2) years], 42,219 (2.7%) individuals were exposed to high (>10 µg/l), 7356 (0.5%) to high-middle (5-10 µg/l), 60,799 (3.9%) to low-middle (2-5 µg/l), and 1,439,326 (92.9%) to low (<2 µg/l) levels of arsenic in groundwater at baseline, respectively. A dose-response association was observed for exposure to arsenic at birth, which individuals born in areas with high, high-middle, and low-middle arsenic levels in groundwater had 156% [2.56 (2.43-2.70)], 98% [1.98 (1.80-2.17)], and 47% [1.47 (1.39-1.56)] higher AD risk than those born in low arsenic exposure areas. Similar dose-response relationship exhibited for arsenic exposure defined by the place of residence at young adulthood (at baseline). The sibling analysis yielded similar results for arsenic exposure evaluated at baseline.ConclusionsExposure to higher arsenic levels in groundwater at birth or young adulthood was associated with an increased risk of AD.