Gout and hyperuricemia continue to rise in the U.S.

Gout rates—and related cases of hyperuricema—have increased over the past two decades, according to research presented at the Nov 2010, American College of Rheumatology Annual Scientific Meeting in Atlanta.

Hyperuricemia is an abnormally high level of uric acid in the blood that can lead to gout - a painful and potentially disabling form of arthritis that has been recognized since ancient times. Initial symptoms of gout usually consist of intense episodes of painful swelling in single joints, most often in the feet (especially the big toe). Gout occurs when excess uric acid (a normal waste product) accumulates in the body, and needle‐like crystals deposit in the joints. This may happen because uric acid production increases or, more often, the kidneys are unable to remove uric acid from the body adequately.

The prevalence of gout in the United States more than doubled between the 1960s and 1990s, but many have been unsure whether the trend continued over the past two decades. To determine if it continued, researchers recently compared the number of U.S. adults diagnosed with gout using two National Health and Nutrition Examination Surveys—NHANES III 1988-1994 and NHANES 2007-2008—which are a group of surveys used to assess the health and nutrition of American adults and children. They also used the same surveys to compare prevalence of hyperuricemia and average serum urate levels between the same time periods.

The 2007-2008 survey included 5,707 participants who were at least 20 years old—of which 2,797 were men and 2,910 were women—to estimate the overall prevalence of gout during this time period. The prevalence was then compared to data from the 1988-1994 survey that included 18,825 participants who were at least 20 years old - of which 8,816 were men and 10,009 were women. The researchers then used the same data and surveys to measure hyperuricemia (defined, for this study, as having serum urate level greater than 7.0mg/dL in men and greater than 5.7 mg/dL in women).

During the 2007-2008 timeframe, researchers identified the overall prevalence of gout among U.S. adults as 8.3 million, which corresponded to 3.9 percent of U.S. adults. This is 1.2 percent higher than the 1988-1994 timeframe figure of 2.7 percent, and researchers attribute this increase to increased gout prevalence among men and senior citizens. Over the same time period, hyperuricemia prevalence increased by 3.2 percent (from 18.2 percent to 21.4 percent), and average serum urate levels also rose by 0.15 mg/dl.

Given these findings, the researchers concluded that the number of U.S. adults with gout not only remained substantially high, but may have increased, after the 1990s. In addition, the results revealed that as gout rates went up, the rates of hyperuricemia also rose, reconfirming the connection between the two.

"These findings indicate that the prevalence of gout and hyperuricemia continue to be substantial in the new millennium," explains Yanyan Zhu, PhD; research assistant professor at the Boston University School of Medicine and lead investigator in the study. "Factors contributing to the increase are also heightening additional risk factors including obesity and hypertension, and better management could help prevent the further rise of gout and other associated complications."