Researchers from Boston University School of Medicine found that women with serum uric acid levels over 5 mg/dl had a significantly lower risk of developing gout than men. This study, the first to examine the relationship between uric acid levels and gout risk in women, also evaluated purported risk factors for gout and found that increasing age, obesity, hypertension, alcohol use, and diuretic use to be among leading contributors for women.
Results of this 52-year follow-up study are published in the April issue of Arthritis & Rheumatism, a journal of the American College of Rheumatology.
Gout is a common and excruciatingly painful inflammatory arthritis caused by elevated uric acid levels in the blood. When too much uric acid builds up in joint fluid, uric acid crystals form and cause joint swelling and inflammation. Historically, gout was seen as a male disease, however growing evidence suggests the disease is also a concern for older women. According to the Third National Health and Nutrition Examination Survey (NHANES-III) the prevalence of gout in women was 3.5% for ages 60-69 years, 4.6% in the 70-79 age group, and 5.6% in those 80 or older. Furthermore, the Rochester Epidemiology project study found the incidence of gout has doubled among women over the past 20 years.
The research team led by Hyon Choi, M.D., D.Ph., analyzed data from the Framingham Heart Study for 2,476 women and 1,951 men who had a complete follow-up history and who were free of gout at baseline. The mean age at baseline was 47 years for women and 46 years for men. Researchers evaluated serum uric acid levels and risk factors for gout that included: age, body mass index (BMI), alcohol consumption, hypertension, medication use (diuretics, hormone replacement therapy), blood glucose and cholesterol levels, and menopause status. At baseline the mean serum uric acid level was 4.0 mg/dl for women and 5.1 mg/dl for men.
"We identified 104 gout cases in women and 200 in men over the 28-year median follow-up period," said Dr. Choi. "The gout incidence per 1,000 person-years was 1.4 in women and 4.0 in men." Specifically, results showed that the incidence rates of gout for women per 1,000 person-years according to serum uric acid levels of <5.0, 5.0-5.9, 6.0-6.9, 7.0-7.9, and ≥8.0 mg/dl were 0.8, 2.5, 4.2, 13.1, and 27.3, respectively.
Results also found among the purported risk factors for gout, increasing age, obesity, alcohol consumption, diuretic use, and hypertension were independently associated with higher risk of gout incidence in women. However, researchers found only a stronger age effect among women placed them at higher risk factors for gout than men. The age-adjusted relative risk (RR) of gout in post-menopausal women was 4.18 and the RR for gout in women using hormone replacement therapy was 0.24. Other risk factors did not differ significantly between women and men.
"Our study found that higher levels of uric acid in the blood increase the risk gout risk for women in a graded manner," concluded Dr. Choi. The risk of gout among women with serum uric acid levels ≥8 mg/dl was 46 times higher than that among women whose levels were <5 mg/dl. However, results show the magnitude of the association between gout and uric acid blood levels among women was significantly lower than for men. "Confirming our results using specific case definitions (observation of urate crystal in joint fluid) would provide to be a valuable contribution to understanding gout incidence in both sexes."
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