High serum uricc acid levels areassociated with an increased risk of allcauseand cardiovascular (CV) mortality,but not cancer mortality, among elderlyindividuals, according to a recent study.
The study, led by Chung-Pin Li,MD, PhD, of Taipei Veterans GeneralHospital in Taiwan, included 77,541participants aged 65 years and olderidentified using the Taipei GeriatricHealth Examination Database. Thegroup included 39,365 men and 38,176women. During an average of 3.3 yearsof follow-up, 3,842 subjects (5%) died.
Compared with the lowest quartile ofserum uric acid level (less than 5.4 mg/dL), the highest quartile (greater than 7.3mg/dL) was associated with a significant17% increased risk of all-cause mortalityamong both men and women, Dr. Li’sgroup reported online ahead of print inthe Journal of the American GeriatricsSociety. The second and third quartiles(5.4–6.3 and 6.4–73 mg/dL, respectively)were associated with a significant 20%and 11% decreased risk of all-cause mortality,respectively, in men, and the thirdquartile was associated with a significant36% increased risk in women.
The highest quartile of serum uricacid level was associated with a significant39% increased risk of cardiovascularmortality in men and a 35%increased risk in women. The secondquartile, however, was associated witha significant 26% decreased risk of cardiovascularmortality in men.
The researchers also looked at theeffect of high versus normal uric acidlevels on the risk of all-cause and cardiovascularmortality. The cutoff was 7 mg/dL for men and 6 mg/dL for women.Compared with normal uric acid levels,high levels were associated with a significant17% and 39% increased risk ofall-cause and cardiovascular mortality,respectively, in men, and 17% and 35%increased risk in women.
According to the researchers, theassociation between uric acid and CVmortality is independent of otherCV risk factors, such as diabetes mellitus,hyperlipidemia, and hypertension.
The investigators found no significantassociation between serum uric acidlevel and cancer mortality risk in eithermen or women.
Dr. Li and colleagues noted that manyin-depth studies have investigated theassociation between hyperuricemiaand mortality, but these studies mainlyincluded middle-aged individuals.“Elderly adults have a higher prevalenceof hyperuricemia and a higherrisk of developing cardiovascularevents or mortality,” the authors wrote.“Because the elderly population isgrowing, a better understanding of therole of serum uric acid as a risk factorfor mortality is merited.”
Strengths of the study include its largesample size, detailed assessment andadjustment for risk factors, and reliableassessment of the cause of death, theinvestigators noted. They also acknowledgedlimitations. For example, uricacid levels were measured only once,“so the effect of changes in serum uricacid levels during follow-up on mortalityrisk could not be investigated.” Inaddition, they researchers did not haveinformation available on the severity ofpre-existing diseases or the use of medicationsby participants, so they couldnot examine the possible confoundingeffects of diuretics on the associationbetween uric acid level and mortality.
In a previous study published in theAmerican Journal of Kidney Diseases(2014;64:550-557), researchers whoanalyzed data from 10,956 participantsin the National Health and NutritionExamination Survey (1988–1994 and1999–2002) found that high uric acidlevels were associated with an increasedrisk of CV and all-cause mortality, butthe relationship was no longer statisticallysignificant after adjusting for kidneyfunction.
Although the current study did notfind a significant association betweenhigh uric acid levels and cancer mortalityrisk, previous studies have. For example,researchers in The Netherlandsfound that elevated serum uric acidlevels were associated with a decreasedrisk of cancer mortality, according tofindings published in Cancer Causes &Control (2014;25:1075-1080).
The study included 1,823 men in ageneral population-based cohort whohad serum uric acid data available. Ofthese, 254 (13.9%) died from any cancer.Serum uric acid levels in the highest tertile(above 5.8 mg/dL) were associatedwith a 32% decreased risk of any cancercompared with levels in the lowest tertile(less than 5.0 mg/dL).
Findings from another study, however,suggest that high serum uric acid levelsincrease cancer mortality risk. Thestudy examined prospective data froma cohort of 83,683 apparently healthyAustrian adults who had a median follow-up of 13.6 years. Compared withmen in the lowest quintile of serum uricacid level, those in the highest quintilehad a 41% increased risk of deathfrom any cancer in adjusted analyses,the investigators reported in CancerCauses & Control (2007;18:1021-1029).Participants younger than 65 years hada 53% increased risk.