High Levels of Uric Acid Could Cause High Blood Pressure

Newswise — People with hyperuricemia are at an increased risk for high blood pressure, according to research presented this week at the 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.

It has long been known that people with high levels of uric acid in the blood can also have high blood pressure. However, it is unknown if these two conditions simply tend to occur together or if one condition actually precedes the other. Researchers recently set out to establish whether excessive uric acid increases the risk for future development of hypertension. They reviewed all previously published studies related to this topic and combined the outcomes of those studies into one overall analysis.

To do this, they searched major electronic databases using specific medical terms associated with hyperuricema and high blood pressure and evaluated hypertension studies that measured the impact of serum uric acid levels. They conducted an analysis of 18 studies that included at least 100 participants of all ages who were studied for at least one year and who did not have high blood pressure at the beginning of the study in which they participated.

According to Peter Grayson MD, a rheumatologist at the Boston Medical Center and lead investigator in the study, most of the studies his team reviewed accounted for factors that are traditionally known to increase the likelihood of developing high blood pressure – such as age, family history, weight and tobacco use. By doing this, Dr. Grayson and his team were able to determine if uric acid independently increases the risk for hypertension.

Among the 18 studies analyzed, there was data from 55,607 participants, including 13,025 participants with high blood pressure. The researchers noted that participants with hyperuricemia were more than 40 percent more likely to later develop high blood pressure than participants without hyperuricemia. Women with the highest uric acid levels and people who develop high levels of uric acid at a relatively young age are especially at risk for developing high blood pressure.

Additionally, race may play an important role, and the researchers noted that black people with hyperuricemia may also be at particularly increased risk.

“The results of this study show that people with elevated uric acid levels are at an increased risk for the future development of hypertension, but this does not mean that uric acid directly causes elevated blood pressure. More studies are needed to clarify that question,” explains Dr. Grayson. “Medications that lower uric acid levels in the blood may potentially be useful in the prevention or treatment of hypertension. Randomized trial data, with particular attention paid to gender, age, and racial subgroups, would be valuable to address this issue.”

The American College of Rheumatology is an international professional medical society that represents more than 8,000 rheumatologists and rheumatology health professionals around the world. Its mission is to advance rheumatology. The ACR/ARHP Annual Scientific Meeting is the premier meeting in rheumatology. For more information about the meeting, visit www.rheumatology.org/education or join the conversation on Twitter by using the official hashtag: #ACR2010.

Editor’s Notes: Peter C. Grayson, MD will present this research during the ACR Annual Scientific Meeting at the Georgia World Congress Center at 5:45 PM on Wednesday, November 10 in Room A 404. Dr. Grayson will be available for media questions and briefing at 8:30 AM on Wednesday, November 10 in the on-site press conference room, B 212

Learn more about living well with rheumatic disease as well as rheumatologists and the role they play in health care.

Presentation Number: 2155

Independent Impact of Hyperuricemia on the Future Risk of Hypertension: A Systematic Review and Meta-Analysis

Peter C Grayson, MD (Boston University School of Medicine, Boston Mass.) Seo Young Kim, MD (Medicine/DOPE, Brigham & Women's Hospital, Boston, Mass.)Michael P LaValley, PhD (Biostatistics, Boston University School of Public Health, Boston, Mass.) Hyon K Choi, MD, DrPH (Rheum/Dept of Med, University of British Columbia, Vancouver, BC)

Body: Purpose: A novel rodent model and a recent randomized trial of hyperuricemic adolescents with hypertension suggest a pathogenetic role of uric acid in hypertension, but it remains unknown whether these findings apply to adult populations where the larger disease burden exists. We conducted a systematic review and meta-analysis to determine if hyperuricemia was associated with incident hypertension, particularly in demographic subgroups.

Methods: We searched major electronic databases using Medical Subject Headings and keywords without language restrictions (through April 2010). Studies with data on incident hypertension related to serum uric acid levels were eligible for inclusion. We only included (1) prospective cohort studies without age restrictions; (2) at least 1 year of follow-up; (3) sample sizes of at least 100 subjects; and (4) inception cohorts free of hypertension. Hyperuricemia was analyzed both as a categorical and continuous variable, and pooled estimates of both unadjusted and adjusted risk ratios (RRs) for incident hypertension were calculated using a random-effects model. The I2 - value was calculated to evaluate between-study heterogeneity. We analyzed age, gender, and race subgroups and performed meta-regression to explore any detected heterogeneity.

Results: A total of 18 prospective cohort studies representing data from 55,607 participants and 13,025 incident hypertension cases were included. Hyperuricemia was associated with an increased risk of incident hypertension (unadjusted risk ratio (RR) 1.81, 95% confidence interval (CI): 1.55-2.07). When using adjusted values, the pooled RR was 1.41 (95% CI: 1.23-1.58) and there was high heterogeneity among included studies (I2 = 0.75, p<0.01). For a 1 mg/dl increase in uric acid level, the pooled adjusted RR for incident hypertension was 1.13 (95% CI, 1.06-1.20). These RRs were significantly larger in younger study populations (p=0.02) and tended to be larger in women (p=0.06). Two studies suggested that the RR may also be larger among black individuals. Furthermore, later publication year and US-based studies were significantly associated with lower RR estimates (p-values <0.02).

Conclusion: Hyperuricemia is associated with an increased risk for incident hypertension, independent of traditional hypertension risk factors. Risk for future hypertension appears more pronounced in hyperuricemic younger individuals and women and appears diminished in US-based studies and studies conducted more recently.

Disclosure: Peter Grayson, nothing to disclose; Seo Young Kim, nothing to disclose; Michael LaValley, nothing to disclose; Hyon Choi, nothing to disclose.

View press release with full abstract at www.rheumatology.org