Neurodegenerative diseases among miners in Ontario, Canada, using a linked cohort.

OBJECTIVES: We examined employment in mining occupations and industries and its association with neurological disease incidence in a linkage cohort from Ontario, Canada. Outcomes included Alzheimer's disease (alone and with other dementias), Parkinson's disease, parkinsonism, motor neuron disease and amyotrophic lateral sclerosis (ALS). METHODS: The Occupational Disease Surveillance System cohort was created by linking workers' compensation data and healthcare usage records. This analysis included over 1.1 million male workers, followed between 1999 and 2016. Neurological diseases were ascertained using physician billing and hospital discharge records. Adjusted Poisson regression models were used to estimate incidence rate ratios (RR) comparing mining to non-mining workers overall and by ore (industry) and occupation group. RESULTS: Suggested elevations in incidence rates were observed for ALS among workers of metal mines (RR 2.21, 95% CI 1.04 to 4.69) and for motor neuron disease among those employed in mining occupations within metal mining industries (RR 1.96, 95% CI 1.01 to 3.79), though these were based on relatively few cases. In miscellaneous metal mines, workers who held mining occupations had an elevated rate of Alzheimer's disease (RR 1.27, 95% CI 0.92 to 1.77). Parkinson's disease rate was elevated among workers with rock and soil drilling occupations (RR 1.60, 95% CI 1.04 to 2.45). CONCLUSIONS: Mining hazards may be associated with elevated rates of neurodegenerative diseases among workers in mining occupations and industries. More work is needed to better understand mining exposures and their associations with neurodegenerative diseases.