Associations between blood lead, olfaction and fine-motor skills in elderly men: Results from the Heinz Nixdorf Recall Study.

Lead (Pb) is a recognized neurotoxin. Pb can interfere with divalent metal transporters and ion channels and may thus affect other brain metals and cation signaling in neurons. Thereby, cognitive and sensory functions can be impaired. Whereas cognitive effects are well described less is known about olfaction and motor functions in the general population at currently lower exposure levels. The objective of this study was to evaluate the influence of Pb in blood (PbB) on odor identification and fine motor skills within the framework of the Heinz Nixdorf Recall Study (HNRS), a prospective cohort study among an elderly German population. Data on odor identification assessed with Sniffin' sticks and fine motor test results were collected during the second follow-up of HNRS (2011-2014) in 1188 elderly men aged 55 to 86 years. PbB was determined in 1140 blood samples archived at baseline (2000-2003) and in 796 samples from the second follow-up. The association between PbB and impaired odor identification (normosmia as reference) was estimated with proportional odds ratios (PORs) with 95% confidence intervals (CI). The odds ratios (OR) of substantially impaired dexterity (tapping hits <10th percentile, errors in aiming, line tracing, or steadiness>90th percentile) were estimated with mixed logistic regression models for test results with both hands, where PbB was adjusted for covariates. PbB at baseline (median 32.9 μg/L; 2.27% ≥90 μg/L) was higher than at follow-up (25.9 μg/L; 0.84% ≥90 μg/L). The individual concentrations were correlated (Spearman r 0.59, 95% CI 0.54 - 0.63). PORs of an impaired odor identification in men with baseline PbB ≥90 μg/L were 1.96 (95% CI 0.94-4.11) and 1.57 (95% CI 0.47-5.19) with follow-up PbB. Fine-motor tests were not affected by elevated PbB with the exception of tapping in men with follow-up PbB ≥50 μg/L (OR 2.14, 95% CI 1.09-4.23). Increasing age had strong effects on all outcomes. Low education was associated with impaired odor identification, tapping, and aiming. Also, alcohol consumption and current smoking affected the test results, particularly steadiness. In this community-based cohort of elderly men, we could confirm indication of an influence of elevated PbB on odor identification. Small numbers of men with elevated PbB due to an on-going trend of decreasing PbB in the general population, strong covariates and multiple comparisons hamper the evaluation of adversity of these effects of PbB on olfaction and dexterity.