Cognitive impairment of workers in a large-scale aluminium factory in China: a cross-sectional study

OBJECTIVES: To investigate the prevalence of mild cognitive impairment and the relationship with plasma aluminium among aluminium workers. DESIGN: This was a cross-sectional case-control study in the SH Aluminium Factory, China. SETTING: The university and affiliated hospital cooperated in the study. PARTICIPANTS: There were 910 aluminium workers on duty, among whom 853 participated in our study. Participants, such as those with cerebral vascular disease, epilepsy, brain trauma, Parkinson’s and mental diseases, aluminium-containing drug and mental drug use, and any family history of dementia in first-degree relatives were excluded. PRIMARY AND SECONDARY OUTCOME MEASURES: Blood samples were collected, and plasma aluminium was measured by inductively coupled plasma-mass spectrometry. For each case, four age-matched controls were evaluated to determine the relationship between aluminium exposure and mild cognitive impairment. Conditional logistic regression was used to explore influential factors in mild cognitive impairment. RESULTS: Among 910 workers, 93.74% participated in stage 1; 53 cases were finally diagnosed. The crude prevalence of mild cognitive impairment among aluminium workers on duty was 6.21%. There was a significant difference in plasma aluminium concentration between the two groups. In the multivariate analysis, we found that a higher level of plasma aluminium was associated with a high risk of cognitive impairment when compared with a lower aluminium level (AOR=2.24, 95% CI=1.17 to 4.26), and a high education level was a protective factor (AOR=0.36, 95% CI=0.18 to 0.70). No other factor was statistically significant. CONCLUSIONS: Mild cognitive impairment is no longer a disease specific to elderly people. High plasma aluminium exposure might be associated with an increased risk of cognitive impairment, but a reduced risk was observed with a high education level. The cognitive function of aluminium workers on duty must be considered seriously.