Age and secular trends in bone lead levels in middle-aged and elderly men: three-year longitudinal follow-up in the Normative Aging Study.

The goal of this study was to examine age and secular trends in bone and blood lead levels of community-exposed men. Bone and blood lead levels were measured twice, with a 3-year interval between measurements, among participants in a longitudinal study of aging. Seventy subjects (mean age = 66 years, age range = 52-83 years) with repeated measurements of bone and blood lead levels were studied. At the first evaluation, geometric mean lead levels in patella, tibia, and blood were 29.1 (standard deviation (SD) 1.8) microg/g, 17.5 (SD 2.0) microg/g, and 6.7 (SD 1.8) microg/dl, respectively. At the second evaluation, these levels were 22.2 (SD 1.8) microg/g, 17.9 (SD 1.7) microg/g, and 5.1 (SD 1.4) microg/dl, respectively. Cross-sectional analysis of each set of measurements indicated that, on average, a 1-year-older individual would have 2.7% and 2.4-3.2% higher levels of lead in patella and tibia, respectively. In contrast to the increasing age trend in cross-sectional analysis, the secular trend over time was decreasing for patella lead levels and stable for tibia lead levels. The authors conclude that in community-exposed middle-aged and elderly men, the biomarkers of exposure to lead are decreasing in patella and blood and unchanging in tibia as of the early 1990s. The increasing age trend in bone lead levels in cross-sectional studies should be carefully interpreted in light of the birth cohort effect.