Long-Term occupational exposure to heavy metals (lead, mercury, aluminum) and risk of dementia: A systematic review and meta-analysis

Background: Dementia, is a major global health challenge. Occupational exposure to heavy metals such as lead, mercury, and aluminum is common in several industries, yet their long-term contribution to dementia risk remains uncertain. Objective: To systematically review and meta-analyze epidemiological evidence on the association between chronic occupational exposure to lead, mercury, or aluminum and risk of dementia or AD. Methods: Following PRISMA 2020 guidelines, PubMed, Web of Science, and Embase were searched through August 2025 for observational studies assessing long-term occupational heavy metal exposure and dementia outcomes. Study quality was assessed using the Newcastle–Ottawa Scale. Random-effects meta-analyses pooled odds ratios (ORs), and heterogeneity was evaluated using the I² statistic. Results: Fifteen studies involving over 10,000 participants met inclusion criteria. Chronic lead exposure was not significantly associated with dementia risk (OR ≈ 1.10, 95% CI 0.90–1.35). Mercury exposure showed a non-significant trend toward increased risk (OR ≈ 1.15, 95% CI 0.80–1.60). In contrast, chronic aluminum exposure was associated with a significantly higher risk of dementia (OR ≈ 1.50, 95% CI 1.20–1.90), with moderate heterogeneity. Conclusion: Long-term aluminum exposure appears to increase dementia risk, whereas evidence for lead and mercury remains inconclusive. Further longitudinal studies with precise exposure assessment are warranted.