Changes in Olfactory discrimination associated to environmental Manganese in Adolescents

Abstract

Introduction: Olfactory changes are frequently shown in Parkinsonian patients and may be related to dysregulation of Dopaminergic control. While studies have suggested that exposure to manganese (Mn) may be associated with Parkinsonism, there is limited information on Mn exposures and the olfactory function in children. Methods: We measured soil and house dust Mn levels in the household of 389 children in Brescia, Italy. Surface soil was assessed with a Niton pXRF instrument and dust samples were collected by sweeping a measured area with a plastic brush, or using a cyclone vacuum. Mn was determined with ICP-OES. To assess odor identification we used Sniffin’ Sticks-Olfactory Screening 12 test (Burghart Medical Technology). We examined the relationships of soil and indoor-outdoor dust Mn (log-transformed) with olfactory discrimination (log-odds of correct identification) using generalized linear models and generalized additive models, adjusting for age, sex, socioeconomic status index, mother education, smoking and drinking. We also tested the effect of environmental Mn using a generalized linear mixed effects model, that allowed us to estimate the difficulty associated with recognizing each of the 12 odors, taking into account the olfactory ability of each subject Results: We found that soil Mn (estimate=-0.125, p=0.02) indoor dust (-0.06, p=0.045) and outdoor dust Mn (estimate=-0.07, p=0.03) were associated with decreased odds of correct odor identifications. This effect was particularly evident in boys. Cloves (when compared with peppermint) was the most difficult odor to be recognized by boys and girls. Conclusions: Our findings suggest that higher environmental Mn levels measured in household dust, outdoor dust and soil may be associated with worse odor identification. These data support the potential influence of Mn on dopaminergic control of olfactory functions that may represent an early sign of neurotoxicity.