The report from the NIH
is based on a Stanford University study, Low-Level Lead Exposure and the Prevalence of Gout: An Observational Study
, done by Eswar Krishnan, MD, MPhil; Bharathi Lingala, PhD; and Vivek Bhalla, MD
The study was reported in the Annals of Internal Medicine
and is the result of interviewing over 6,100 Americans age 40 and up about their health and lifestyle and an analysis of their blood lead levels.
Gout is a sometimes a painfully, debilitating form of arthritis caused by build up of uric acid in the joints. Uric acid is produced in the body after it breaks down a substance known as purines. A natural occurrence in the body but can be also found in some common foods like mushrooms or organ meats. A substance that increases production or slows down the body’s ability to clear uric acid will increase the risk of gout.
The symptoms of gout are mostly experienced in the big toe, with periodic swelling, redness and heat sensation. Other areas that can be affected include feet, ankles, knees, hands and wrists.
There are other contributing factors to the increase of uric acid production such as obesity, high blood pressure, diabetes and kidney disease. And researchers have always cited the condition can be directly linked heavy lead exposure.
However, when all those factors were weighed and added to the participant’s smoking and other habits, the lead levels were still connected to the increase risk for gout.
People in the top 25 percent for lead levels had the highest gout risk: four times higher than people in the bottom 25 percent.
That top group had lead levels ranging from 2.6 to 27 mcg/dL, according to the researchers, but most were well below the acceptable lead threshold. Only three people in the study had lead levels of 25 mcg/dL or higher, while 31 had levels of 10 mcg/dL or higher.
“The theory is that even small amounts of lead can hinder the kidneys’ ability to excrete uric acid.” said Dr. Krishnan
Dr. Ashwini R. Sehgal, who was interviewed by Reuters
, stated, “many people with elevated lead levels are exposed to the metal at work - in industries like mining, construction and battery making.”
He suggested letting a physician know if one suspects or knows they've worked with lead to see if a test is warranted. But added that he didn’t feel that everyone needed their blood checked.
Other factors besides work where people can be exposed to lead were noted by Dr. Krishnan: Cigarette smoke contains lead; lead-containing dust; deteriorating lead-based paint in an older home, creating lead-containing dust; drinking water, particularly in older homes with lead pipes. He mentioned that certain hobbies like working on cars, making glazed pottery or stained glass also expose us to lead.
The U.S. Centers for Disease Control and Prevention recently lowered the maximum acceptable lead level for children - from 10 mcg/dL to 5 mcg/dL. The threshold for children is lower because their developing brains are particularly vulnerable to damage from lead.
The Lancet Journal
Gout is becoming common in the U.S. with rates doubling between 1990 and 2010, and is twice as likely in African American males vs European Americans males.
Without treatment, an acute attack of gout usually resolves in five to seven days. However, 60% of people have a second attack within one year.
Episodes of acute gout may develop into chronic gout with destruction of joint surfaces, joint deformity, and painless tophi. These tophi occur in 30% of those who are untreated for five years, often in the helix of the ear, over the olecranon processes, or on the Achilles tendons. With aggressive treatment, they may dissolve. Kidney stones also frequently complicate gout, affecting between 10 and 40% of people, and occur due to low urine pH promoting the precipitation of uric acid. Other forms of chronic renal dysfunction may occur.
Lower lead thresholds were suggested by Dr. Sehgal, who reported the standards are 7 mcg/dL for women and 9 mcg/dL for men in Germany and are doable in the U.S. An editorial written by him, Redefining Toxic Lead Levels Among Adults
, accompanies the study paper.