Cumulative lead exposure in community-dwelling adults and fine motor function: comparing standard and novel tasks in...

Lead exposure in children and occupationally exposed adults has been associated with reduced visuomotor and fine motor function. However, associations in environmentally exposed adults remain relatively unexplored. To address this, we examined the association between cumulative lead exposure-as measured by lead in bone-and performance on the grooved pegboard (GP) manual dexterity task, as well as on handwriting tasks using a novel assessment approach, among men in the VA Normative Aging Study (NAS).

GP testing was done with 362 NAS participants, and handwriting assessment with 328, who also had tibia and patella lead measurements made with K-X-Ray Fluorescence (KXRF). GP scores were time (s) to complete the task with the dominant hand. The handwriting assessment approach assessed the production of signature and cursive lowercase l and m letter samples. Signature and lm task scores reflect consistency in repeated trials. We used linear regression to estimate associations and 95% confidence intervals (CI) with adjustment for age, smoking, education, income and computer experience. A backward elimination algorithm was used in the subset with both GP and handwriting assessment to identify variables predictive of each outcome.

The mean (SD) participant age was 69.1 (7.2) years; mean patella and tibia concentrations were 25.0 (20.7)μg/g and 19.2 (14.6)μg/g, respectively. In multivariable-adjusted analyses, GP performance was associated with tibia (β per 15μg/g bone=4.66, 95% CI: 1.73, 7.58, p=0.002) and patella (β per 20μg/g=3.93, 95% CI: 1.11, 6.76, p=0.006). In multivariable adjusted models of handwriting production, only the lm-pattern task showed a significant association with tibia (β per 15μg/g bone=1.27, 95% CI: 0.24, 2.29, p=0.015), such that lm pattern production was more stable with increasing lead exposure. GP and handwriting scores were differentially sensitive to education, smoking, computer experience, financial stability, income and alcohol consumption.

Long-term cumulative environmental lead exposure was associated with deficits in GP performance, but not handwriting production. Higher lead appeared to be associated with greater consistency on the lm task. Lead sensitivity differences could suggest that lead affects neural processing speed rather than motor function per se, or could result from distinct brain areas involved in the execution of different motor tasks.