Gout can be associated with blood levels of lead previously thought acceptable

Gout is a painful inflammatory condition, typically affecting the joint at the base of the big toe but potentially any location where urate crystals due to high blood levels of uric acid have settled. Uric acid is not the whole story, however, some not everyone with high uric acid levels experiences gout. Something has to trigger an immune inflammatory response to the stored uric acid. The authors of research recently published in Annals of Internal Medicine offer evidence that blood levels of lead previously thought acceptable increase the risk for gout. They note that...

"Blood lead levels (BLLs) less than 1.21 µmol/L (<25 µg/dL) among adults are considered acceptable by current national standards. Lead toxicity can lead to gouty arthritis (gout), but whether the low lead exposure in the contemporary general population confers risk for gout is not known."

So they set out to...

"...determine whether BLLs within the range currently considered acceptable are associated with gout."

They examined data on 6153 civilians aged 40 years or older who had taken part in The National Health and Nutrition Examination Survey for 2005 through 2008 for self-reported physician diagnosis of gout and serum urate level with the blood lead level as the principal exposure variable. They also collected data on anthropometric measures, blood pressure, dietary purine intake, medication use, medical history, and serum creatinine concentration. The data definitely incriminated lead as a significant contributing factor:

"The prevalence of gout was 6.05% among patients in the highest BLL quartile (mean, 0.19 µmol/L [3.95 µg/dL]) compared with 1.76% (CI, 1.10% to 2.42%) among those in the lowest quartile (mean, 0.04 µmol/L [0.89 µg/dL]). Each doubling of BLL was associated with an unadjusted odds ratio of 1.74 for gout and 1.25 for hyperuricemia. After adjustment for renal function, diabetes, diuretic use, hypertension, race, body mass index, income, and education level, the highest BLL quartile was associated with a 3.6-fold higher risk for gout and a 1.9-fold higher risk for hyperuricemia compared with the lowest quartile."

A primary concern about heavy metals and other environmental toxins is the possibility of loss of immune tolerance for those agents, with subsequent loss of tolerance for the tissues with which they interact. Lead may be provoking an inflammatory reaction to uric acid depots in this way. I have seen patients with gout whose uric acids levels were only mildly elevated. I will check them for blood lead levels in future. The authors conclude:

"Blood lead levels in the range currently considered acceptable are associated with increased prevalence of gout and hyperuricemia."