— Older men with higher uric acid levels may be at increased risk for hip fracture, researchers reported here.
by Kristina Fiore, Staff Writer, MedPage Today
April 28, 2014
AS VEGAS — Older men with higher uric acid levels may be at increased risk for hip fracture, researchers reported here.
In a prospective cohort study, men ages 65 and up with uric acid levels above 7 mg/dL were 62% more likely than those with lower levels to fracture a hip, Tapan Mehta, MD, of the University of Colorado Denver, and colleagues reported at the National Kidney Foundation spring clinical meetings.
“High uric acid levels appear to be associated with a higher rate of hip fractures in older men,” Mehta said in a statement. “We were not able to find a relationship between uric acid and hip fractures in women, suggesting that other factors are more important in women.”
Research has shown that uric acid, a normal byproduct of cell breakdown, is affected by diet. Sugar and animal products boost uric acid levels, and its harder for kidneys to clear uric acid from blood.
“People with unhealthy dietary habits are more likely to have high uric acid levels,” Mehta said. “And people with kidney disease are more likely to have high uric acid levels.”
Higher levels have been shown to increase the risk of gout and kidney stones, and recent studies have also suggested that they can contribute to high blood pressure, heart disease, and kidney disease.
Mehta and colleagues hypothesized that high uric acid levels may also have an impact on bone health. The research team has previously shown that uric acid inhibits 1-alpha hydroxylase protein expression and activity in vivo, and that higher uric acid levels are associated with higher parathyroid hormone levels, suggesting a link between uric acid and bone health.
They assessed data from the Cardiovascular Health Study on 4,692 patients — 1,963 men and 2,729 women — who had baseline uric acid levels taken.
During an 11-year follow-up period, 156 hip fractures occurred.
Among men, 430 had uric acid levels above 7 mg/dL (mean 8.08 mg/dL), compared with a normal range of 3.5 to 7.2 mg/dL.
These men were more likely to be obese, had significantly higher values of insulin, C-reactive protein, cystatin C, and a lower cystatin C glomerular filtration rate (GFR), compared with those who had normal uric acid levels.
Those with higher levels also tended to be black, on diuretics, and not in good health overall, the researchers said.
They found that higher uric acid levels were associated with a significant 62% increase in hip fracture in men compared with those who had lower values (HR 1.62, 95% CI 1.075 to 2.449, P=0.02).
But the relationship did not occur among women, they said. Indeed, some research has found the opposite association in women.
A study in Osteoporosis International reported that higher levels of serum uric acid had a protective effect on bone metabolism in postmenopausal women. In that study osteoporosis risk was 40% higher in women in the lowest quartile of uric acid levels compared with those in the highest quartile.
“We think there are other factors that are related to bone health in women, like estrogen deficiency,” Mehta told MedPage Today.
Mehta said several possible mechanisms may be involved in the association among men. “High uric acid levels may impair nitric oxide availability in the bone, and this may increase bone fragility and fracture risk,” he said.
Also, “uric acid may also induce inflammation in the bone, and this could lead to more fragile bone. In addition, uric acid suppresses vitamin D activation, and this could play a role in the higher risk of fractures,” he said.
Mehta cautioned that because the results are from an observational study, no clinical recommendations can be made at this time.
“Based on this study, we cannot yet recommend that patients with high uric acid be treated to reduce hip fracture risk,” he told MedPage Today. “Further studies are needed to understand the mechanisms behind the association.”
Thomas Manley, director of scientific activities at the National Kidney Foundation, said the results are consistent with other recent literature.
“There have been a number of recent studies showing an association between elevated uric acid and several negative outcomes including more rapid progression of kidney disease,” Manley said in a statement. “Most clinical practice guidelines suggest that more evidence is needed before they would recommend screening for or treating elevated uric acid levels, except in the presence of symptoms of gout to reduce those symptoms.”
“However,” he added, “there are clinical studies now underway evaluating whether lowering uric acid may be beneficial even in the absence of symptoms. This has the potential to be a new therapeutic option to improve outcomes for kidney disease patients, as several of these studies are looking at how treating elevated uric acid impacts the progression of kidney disease.”
Mehta reported no relevant financial disclosures.
LAST UPDATED
Primary Source
National Kidney Foundation