High Lead Levels Increase Risk of Gout

Krishnan E, Lingla B, Bhalla V. Low-level lead exposure and the prevalence of gout. Ann Int Med. 2012;157:233-241.

 

The 2005/6 and 2007/8 NHANES trial was analyzed looking for an association between blood lead levels and gout attacks.

 

Data from 6,153 US residents over the age of 40 were used in the study. Any of the National Health and Nutrition Examination Survey (NHANES) cohort who had diminished kidney function were excluded from the study. The researchers tracked of the amount of purine-containing foods participants consumed. The study accounted for confounding factors that might affect gout risk.

 

The researchers found that those participants with the highest blood lead levels (averaging 3.95 µg/dL) had a risk for gout that was 6.05-fold greater than those with lowest levels. They went on to report that “blood lead levels as low as 1.2 µg/dL can be associated with increased prevalence of gout, independent of other major risk factors, such as renal function, age, sex, race, diabetes, hypertension, use of diuretics and dietary variables.”

 

According to the researchers’ findings, individuals with blood or non-flushed urine lead levels in the 50–75th percentiles have a 94% greater risk of having gout and a 70% greater risk of having elevated uric acid levels. Once the levels reached the 75th percentile, their risk of gout increased by a factor of 2.87 and their risk of hyperuricemia increased by 72%.

 

Another very interesting finding in this study was that those persons with gout did not have higher levels of purines in their diet than those without gout.

 

I rarely get to read articles whose authors have done their homework or thought through potential problems as well the authors of this study. Currently, adult blood levels of lead are considered “toxic” only after they have exceeded 80 µg/dL and are considered “elevated” when they are higher than 25 µg/dL. Fortunately, the Centers for Disease Control and Prevention (CDC) recently dropped the “elevated” level for children from 10 µg/dL to 5 µg/dL,¹ although many current lead researchers consider even that number too high. In the current study, the researchers found that those with the highest blood lead levels (averaging 3.95 µg/dL) had a risk for gout that was 6.05-fold greater than those with the lowest levels. Keep in mind that 3.95 µg/dL is far below the “elevated” status of 25 µg/dL. But that level is smack in the middle of the 90th percentile range (meaning that at 10 percent of the US residents have lead values in this range) reported by the CDC in their 4th national report.²

 

The fact that the prevalence of gout is independently associated with blood lead levels above 1.2 µg/dL is remarkable. This level (1.2 µg/dL) is below the CDC’s mean. The detection limit from Lab Corp for blood lead is 1 µg/dL, so standard lab blood tests can spot this risk. For those using pre-challenge urinary lead levels, this would be just below 0.632 µg/g creatinine (the CDC mean for urinary lead in the same report).

 

 

 

This excellently conducted study gives clinicians another reason to check baseline (non-challenged) urine heavy metal levels or blood lead levels for our patients who are over 40 and who are experiencing either gout or hyperuricemia. It also highlights the fact that the old blood standards for heavy metal toxicity, which came straight from the industries that use those heavy metals, are not good indicators of whether those toxicants are at levels that can cause ill health.