High Uric Acid Levels Up Death Risk in the Elderly
Highest vs. lowest quartile associated with a 17% increased risk.
The study, led by Chung-Pin Li, MD, PhD, of Taipei Veterans General Hospital in Taiwan, included 77,541 participants aged 65 years and older identified using the Taipei Geriatric Health Examination Database. The group included 39,365 men and 38,176 women. During an average of 3.3 years of follow-up, 3,842 subjects (5%) died.
Compared with the lowest quartile of serum uric acid level (less than 5.4 mg/ dL), the highest quartile (greater than 7.3 mg/dL) was associated with a significant 17% increased risk of all-cause mortality among both men and women, Dr. Li's group reported online ahead of print in the Journal of the American Geriatrics Society. 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 third quartile was associated with a significant 36% increased risk in women.
The highest quartile of serum uric acid level was associated with a significant 39% increased risk of cardiovascular mortality in men and a 35% increased risk in women. The second quartile, however, was associated with a significant 26% decreased risk of cardiovascular mortality in men.
The researchers also looked at the effect of high versus normal uric acid levels on the risk of all-cause and cardiovascular mortality. 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 significant 17% and 39% increased risk of all-cause and cardiovascular mortality, respectively, in men, and 17% and 35% increased risk in women.
According to the researchers, the association between uric acid and CV mortality is independent of other CV risk factors, such as diabetes mellitus, hyperlipidemia, and hypertension.
The investigators found no significant association between serum uric acid level and cancer mortality risk in either men or women.
Dr. Li and colleagues noted that many in-depth studies have investigated the association between hyperuricemia and mortality, but these studies mainly included middle-aged individuals. “Elderly adults have a higher prevalence of hyperuricemia and a higher risk of developing cardiovascular events or mortality,” the authors wrote. “Because the elderly population is growing, a better understanding of the role of serum uric acid as a risk factor for mortality is merited.”
Strengths of the study include its large sample size, detailed assessment and adjustment for risk factors, and reliable assessment of the cause of death, the investigators noted. They also acknowledged limitations. For example, uric acid levels were measured only once, “so the effect of changes in serum uric acid levels during follow-up on mortality risk could not be investigated.” In addition, they researchers did not have information available on the severity of pre-existing diseases or the use of medications by participants, so they could not examine the possible confounding effects of diuretics on the association between uric acid level and mortality.
In a previous study published in the American Journal of Kidney Diseases (2014;64:550-557), researchers who analyzed data from 10,956 participants in the National Health and Nutrition Examination Survey (1988–1994 and 1999–2002) found that high uric acid levels were associated with an increased risk of CV and all-cause mortality, but the relationship was no longer statistically significant after adjusting for kidney function.
Although the current study did not find a significant association between high uric acid levels and cancer mortality risk, previous studies have. For example, researchers in The Netherlands found that elevated serum uric acid levels were associated with a decreased risk of cancer mortality, according to findings published in Cancer Causes & Control (2014;25:1075-1080).
The study included 1,823 men in a general population-based cohort who had serum uric acid data available. Of these, 254 (13.9%) died from any cancer. Serum uric acid levels in the highest tertile (above 5.8 mg/dL) were associated with a 32% decreased risk of any cancer compared with levels in the lowest tertile (less than 5.0 mg/dL).
Findings from another study, however, suggest that high serum uric acid levels increase cancer mortality risk. The study examined prospective data from a cohort of 83,683 apparently healthy Austrian adults who had a median follow- up of 13.6 years. Compared with men in the lowest quintile of serum uric acid level, those in the highest quintile had a 41% increased risk of death from any cancer in adjusted analyses, the investigators reported in Cancer Causes & Control (2007;18:1021-1029). Participants younger than 65 years had a 53% increased risk.