Background/Purpose: We have previously identified associations between whole blood lead (Pb) and knee osteoarthritis (OA) and with biomarkers of joint metabolism.  We hypothesized that Pb may be associated with burden of OA as assessed by multiple joint radiographs and symptoms.

Methods: Whole blood Pb concentrations, representing recent exposure and Pb mobilized from bone, were determined at the Centers for Disease Control and Prevention using inductively coupled plasma-dynamic reaction cell-mass spectrometer analysis; levels were categorized into quartiles for analysis. We used composite scores obtained from previously described factor analysis (1) of radiographic OA (rOA) scores from the hands, knees, and spine, and symptoms scores of the low back, hands, knees, and hips, to reflect body burden of OA as outcome measures (categorized due to non-normal distributions).  Generalized logit and proportional odds models were used for these multi-level outcomes, and were adjusted first for age, body mass index (BMI), race, and sex, and then additionally for the other joint site scores.

Results: This cross-sectional analysis includes data (collected at a single visit during 2003-8) for 1659 individuals, 33% male and 35% African American with a mean age of 65 years and BMI 30 kg/m².  At individual sites, rOA with symptoms was present in 13% for hand, 12% for hip, 24% for knee, and 28% for spine.  Whole blood Pb was associated with spine rOA scores (30% increased odds of having higher spine rOA scores in the highest Pb quartile compared to the lowest, adjusted OR 1.34 [95% CI 1.01-1.77]), although this was no longer significant after adjustment for the composite scores of other joint sites (Table).  The composite score of symptoms, however, was associated with Pb in models adjusted for covariates (OR 1.84 [95% CI 1.41, 2.40]) and after adjustment for rOA scores (Table), such that those in the highest quartile of Pb had 70-85% higher odds of reporting more symptoms compared to those in the lowest Pb quartile. 

Conclusion: There was a statistically significant positive association between blood Pb levels and the composite symptoms score, reflecting symptoms at multiple joint sites. No associations were seen for multiple joint rOA in this cross-sectional study.

1. Nelson AE et al, Arthritis Res Ther 2011;13:R76.