Whole blood lead levels are associated with radiographic and symptomatic knee osteoarthritis: a cross-sectional analysis in the Johnston County Osteoarthritis Project

Abstract

IntroductionLead (Pb) is known to affect bone, and recent evidence suggests that it has effects on cartilage as well. As osteoarthritis (OA) is a highly prevalent disease affecting bone and cartilage, we undertook the present analysis to determine whether whole blood Pb levels are associated with radiographic and symptomatic OA (rOA and sxOA, respectively) of the knee.MethodsThe analysis was conducted using cross-sectional data from the Johnston County Osteoarthritis Project, a rural, population-based study, including whole blood Pb levels, bilateral posteroanterior weight-bearing knee radiography and knee symptom data. rOA assessment included joint-based presence (Kellgren-Lawrence (K-L) grade 2 or higher) and severity (none, K-L grade 0 or 1; mild, K-L grade 2; moderate or severe, K-L grade 3 or 4), as well as person-based laterality (unilateral or bilateral). SxOA was deemed present (joint-based) in a knee on the basis of K-L grade 2 or higher with symptoms, with symptoms rated based on severity (0, rOA without symptoms; 1, rOA with mild symptoms; 2, rOA with moderate or severe symptoms) and in person-based analyses was either unilateral or bilateral. Generalized logit or proportional odds regression models were used to examine associations between the knee OA status variables and natural log-transformed blood Pb (ln Pb), continuously and in quartiles, controlling for age, race, sex, body mass index (BMI), smoking and alcohol drinking.ResultsThose individuals with whole blood Pb data (N = 1,669) had a mean (±SD) age of 65.4 (±11.0) years and a mean BMI of 31.2 (±7.1) kg/m2, including 66.6% women and 35.4% African-Americans, with a median blood Pb level of 1.8 μg/dl (range, 0.3 to 42.0 μg/dl). In joint-based analyses, for every 1-U increase in ln Pb, the odds of prevalent knee rOA were 20% higher (aOR, 1.20; 95% CI, 1.01 to 1.44), while the odds of more severe rOA were 26% higher (aOR, 1.26; 95% CI, 1.05 to 1.50, under proportional odds). In person-based analyses, the odds of bilateral rOA were 32% higher for each 1-U increase in ln Pb (aOR, 1.32; 95% CI, 1.03 to 1.70). Similarly for knee sxOA, for each 1-U increase in ln Pb, the odds of having sxOA were 16% higher, the odds of having more severe symptoms were 17% higher and the odds of having bilateral knee symptoms were 25% higher. Similar findings were obtained with regard to ln Pb in quartiles.ConclusionsIncreases in the prevalence and severity measures for both radiographically and symptomatically confirmed knee OA (although statistically significant only for rOA) were observed with increasing levels of blood Pb, suggesting that Pb may be a potentially modifiable environmental risk factor for OA.

Spatial distribution of the trace elements zinc, strontium and lead in human bone tissue

“…Even metabolic processes in the bone are adversely affected by Pb [44,45,60,63,85]. Further Pb has been stated as a potential risk factor for osteoporosis [23], has negative influences on bone healing mechanisms [96] and might affect the articular cartilage tissue [24]. In the present study no significant differences in the trace element content and distribution pattern between bones from individuals with osteoporotic neck fractures and those from age matched healthy individuals without fractures could be detected.…”

“…Exposure to Pb is associated with chronic diseases in the nervous, hematopoietic, skeletal, renal and endocrine systems [21,22]. Pb has been stated also as a potential risk factor for osteoporosis [23] and osteoarthritis [24]. Approximately 95% of the total body Pb burden is stored in skeleton [25] indicating that the bone tissue has a high capacity to accumulate and store Pb.…”

Social Determinants and Osteoarthritis Outcomes

“…Early studies on environmental exposure and OA have suggested that increasing levels of whole blood lead exposure is associated with small but significant increases in the prevalence and severity of radiographic knee OA [94]. It is currently unclear whether or not this association is explained by a direct toxic effect of lead on joint tissues or through an indirect mechanism, however this preliminary research suggests that features of the environment, such as environmental exposure to this toxicant may play some role in mobility and disability in knee OA.…”

Whole blood lead levels are associated with biomarkers of joint tissue metabolism in African American and white men and women: The Johnston County Osteoarthritis Project

“…Our results suggest that systemic Pb is associated with bone turnover (uNTX-I), as well as mineralized (uCTX-II) among women, and non-mineralized (COMP) cartilage turnover among men, but as this is a cross-sectional analysis, we cannot determine whether cartilage turnover is an indicator, or consequence, of Pb release. The association between blood Pb level and cartilage-associated biomarkers, along with our recent cross-sectional analysis showing associations between blood Pb and radiographic knee osteoarthritis and knee symptoms (Nelson et al 2011), suggests the possibility that Pb may play a role in the pathophysiology of osteoarthritis. Longitudinal studies including assessments of radiographic and symptomatic osteoarthritis, in conjunction with both blood and bone Pb, would be valuable to further evaluate the potential effects of Pb on joint symptoms, onset and progression of this highly prevalent and often debilitating disease.…”