Background
Aluminum and
fluoride are neurotoxic, and
aluminum exposure alone is closely related to the overall
cognitive function of operational
workers. It is unclear about the effect of
aluminum and
fluoride interactions on
cognitive function. Objective To evaluate a potential interaction effect of
blood aluminum and urinary
fluoride on the overall
cognitive function of
workers working in an
aluminum plant.
Methods Using
cluster sampling, 230
workers in the
electrolysis workshop of an
aluminum group company in Shanxi Province were selected, and
plasma aluminum concentrations were determined by inductively coupled
plasma mass spectrometry (ICP-MS) and urinary
fluoride by
ion-selective electrode. The study participants were divided into a low
blood aluminum group and a high
blood aluminum group according to the median (M) of
blood aluminum concentration, and a low urinary
fluoride group and a high urinary
fluoride group by a predetermined cutoff point (2.160 mg·L−1). The Montreal Cognitive Assessment-
Beijing (MoCA-BJ) was used to assess overall
cognitive function of the
workers.
Logistic regression model was used to analyze the relationship between
blood aluminum, urinary
fluoride, and
mild cognitive impairment (MCI), including multiplicative interaction
analysis and correlation
analysis; R
language was used to fit an additive interaction model of
blood aluminum and urinary
fluoride on MCI and to calculate synergy index (S), relative excess
risk due to interaction (RERI), and attributable proportion due to interaction (
API). Results Among the 230 operational
workers, the median
blood aluminum concentration (P25, P75) was 40.11 (25.16, 58.89) µg·L−1, and there were 104 cases of abnormal urinary
fluoride, with an abnormality rate of 45.2%. There was a multiplicative interaction (OR=7.783, 95%CI 1.377, 43.991) and no additive interaction (RERI=0.030, 95%CI −0.498, 0.559;
API=0.018, 95%CI −0.279, 0.316; S=1.049, 95%CI 0.519, 2.118) for the effect between
blood aluminum and urinary
fluoride on overall
cognitive function of the
workers. The
logistic regression analysis showed that the
risk of MCI was 12.105 (95%CI 2.802, 52.287) times higher in
workers with both high
blood aluminum and high urinary
fluoride than in those with low
blood aluminum and low urinary
fluoride, after adjusting for selected influencing factors. Conclusion
Occupational exposure related high
blood aluminum and high urinary
fluoride are
risk factors for
cognitive dysfunction, and the coexistence of both
indicators increases the
risk of MCI in
workers with occupational
aluminum exposure, with a multiplicative interaction.