Tophaceous gout and high level of hyperuricaemia are both associated with increased risk of mortality in patients with gout

Abstract

Background: While several studies have reported a link between the presence of gout and adverse cardiovascular (CV) events in the general population, none has addressed the question of whether the mortality risk of patients with gout is influenced by disease severity.

Methods: We applied survival analysis methodology to prospectively collected data on clinical and radiographic measures of disease severity and mortality in a specialty clinic based cohort of 706 patients with gout (1992-2008). Standardised mortality ratios (SMR) were calculated to assess the magnitude of excess mortality among patients with gout compared with the underlying general population.

Results: Mean follow-up was 47 months. Tophaceous deposition was present in 30.5% of patients; >4 joints were involved in 34.6% of cases. Mean annual flare rate was 3.4. Arterial hypertension (41.2%), hyperlipidaemia (42.2%), diabetes mellitus (20.1%), renal function impairment (26.6%) and a previous CV event (25.3%) were recorded. 64 (9.1%) patients died, death being attributed to vascular causes in 38 (59%) patients. SMR for gout patients was 2.37 (95% CI 1.82 to 3.03), 1.57 (1.18 to 2.05) and 4.50 (2.06 to 8.54) overall, and in men and women, respectively. The presence of tophi and the highest baseline serum urate (SU) levels were independently associated with a higher risk of mortality, in addition to age, loop diuretic use and a history of a previous vascular event. In the multivariable survival regression models, with time varying covariates, the presence of tophi remained a significant mortality risk after adjustment for baseline SU levels (1.98; 1.24 to 3.20).

Conclusions: High baseline SU level and the presence of subcutaneous tophi were both associated with an increased risk of mortality in patients with gout, in most cases attributed to a CV cause. This suggests a plausible pathophysiological link between greater total body urate load and CV disease.

Keywords: Cardiovascular Disease; Gout; Outcomes research.