Impact of occupational aluminum exposure on memory function of male workers

  Objective  To evaluate the impact of occupational aluminum (Al) exposure on memory functions of workers.

  Methods  The study was conducted among 408 male workers (mean age = 43.51 ± 7.21, average working years = 22.82 ± 8.25) from an aluminum factory. Demographics and general information of the workers were collected with a self-designed questionnaire. Montreal Cognitive Assessment Scale (MoCA) (Beijing Edition) and World Health Oganization/University of California at Los Angeles Auditory Verbal Learning Test (AVLT) were adopted in evaluations on the workers′ memory function. Plasma Al concentration was measured with inductively coupled plasma-mass spectrometry to assess the workers′ internal aluminum exposure and the workers were divided into four groups according their quartile values of plasma Al (namely Q₁, Q₂, Q₃, and Q₄ for the lowest, the second, the third, and the highest quartile).

  Results  In analysis of variance (ANOVA), no significant differences were detected in all module scores of MoCA among the workers of the four groups after adjusting for education, age, monthly income per capita, and working years (P > 0.05). The distribution of the scores of all AVLT dimensions were significantly different among the workers of the four groups (P < 0.05), except for long-term delayed recognition (F = 2.195, P = 0.088) after adjusting for confounding variables. The score of the 1st and 2nd immediate memory of the workers with the plasma Al of Q₄ were significantly lower than those of the workers with the plasma Al of other 3 quartiles (P < 0.05 for all). Compared to the workers with the plasma Al of Q₁, the workers with the plasma Al of the Q₃ and Q₄ had significantly decreased scores for the 3rd immediate memory and delayed recall (all P < 0.05). Among the workers of the four groups, there was no significant difference in overall distribution of MoCA scores in ANOVA for retest results (F = 0.821, P = 0.483); while, the distribution of AVLT scores was significantly different (F = 11.214, P < 0.001), with lower scores for the workers with the plasma Al of Q₄ than those of the workers of other groups.

  Conclusion  Occupa-tional aluminum exposure may cause a decrease in sensory and episodic memory function among workers and the Auditory Verbal Learning Test may be more efficient than the Montreal Cognitive Assessment Scale in the evaluation on the memory function impairment among the workers.