MONDAY, Aug. 20, 2012 (MedPage Today) — Adults with supposedly safe blood levels of lead had a significantly higher prevalence of gout and hyperuricemia than did adults with the lowest lead levels, a large population study showed.
An average blood lead level of 3.95 µg/dL was associated with a 6.05 percent prevalence of gout, versus 1.76 percent for people with a mean lead level of 0.89 µg/dL, as reported online in Annals of Internal Medicine. The current national standard for acceptable levels is <25 µg/dL.
Each doubling of blood lead level increased the odds for gout by 1.74 and the odds for hyperuricemia by 1.25, according to Eswar Krishnan, MD, of Stanford University, and co-authors.
After adjustment for population characteristics, people with the highest blood lead levels had more than a threefold greater risk of gout compared with adults with the lowest levels, they reported.
"This study documents that low-level exposure to lead ... as it occurs in the general population is associated with a significantly elevated prevalence of gout," the authors wrote in conclusion. "These data suggest that there is no such thing as a 'safe' level of exposure to lead. Further refinement in national goals for prevention, detection, and removal of lead from the environment should be pursued."
Current standards for acceptable lead exposure might not reflect a true threshold of harm. As an example, the authors cited recent studies showing that blood lead levels <25 µg/dL are associated with progression of chronic kidney disease and with cardiovascular mortality.
Lead toxicity (>80 µg/dL) has established links to hyperuricemia and gout. However, the association remains controversial for lower levels of lead exposure, the authors continued. Population-based studies have yielded contradictory and inconclusive findings.
Krishnan and colleagues undertook a study to examine whether current accepted standards for lead exposure have an association with gout. They also included mercury and cadmium in the study.
Data for the analysis came from the 2005 to 2006 and the 2007 to 2008 National Health and Nutrition Examination Survey (NHANES). The authors limited the search to adults ages 40 to 85 with information on serum creatinine, blood levels of heavy metals, and serum urate concentrations.
They excluded NHANES participants with a history of dialysis, renal disease or glomerular filtration rate <10 mL/min/1.73 m2.
The final analysis included 6,153 participants, distributed evenly between men and women. Of 12,520 serum urate measurements, three study participants (0.05 percent) had blood lead levels ≥25 µg/dL and 31 (0.50 percent) had blood levels ≥10 µg/dL (cutoff for children).
The authors found that 290 study participants had gout, including 229 cases among men. The subgroup with gout was older and had worse renal function and more comorbidities. Gout was associated with significantly higher mean blood lead levels, but not levels of cadmium or mercury.
Analysis of the data with blood lead level as a continuous variable resulted in odds ratios of 1.92 and 1.17 for gout and hyperuricemia, respectively.
The author of an accompanying editorial suggested that clinicians routinely obtain lifetime exposure histories and at least consider measuring blood lead levels. Public health policymakers should reconsider the current blood lead levels accepted as safe.
"Lower thresholds for toxic lead levels are both desirable and feasible," wrote Ashwini R. Seghal, MD, of Case Western Reserve University in Cleveland.
"Lead and its myriad uses will remain an integral part of our external environment. However, both children and adults deserve an internal environment that is as unleaded as was our evolutionary past."
Last Updated: 8/21/2012