The impact of serum uric acid on cardiovascular outcomes in the LIFE study

Abstract

The Losartan Intervention For Endpoint reduction in hypertension (LIFE) study demonstrated the superiority of a losartan-based regimen over atenolol-based regimen for reduction of cardiovascular (CV) morbidity and mortality. It has been suggested that the LIFE study results may be related to the effects of losartan on serum uric acid (SUA). SUA has been proposed as an independent risk factor for CV morbidity and death. Cox regression analysis was used to assess relationship of SUA and treatment regimens with the LIFE primary composite outcome (CV death, fatal or nonfatal myocardial infarction, fatal or nonfatal stroke). Baseline SUA was significantly associated with increased CV events [hazard ratio (HR) 1.024 (95% CI 1.017-1.032) per 10 micromol/L, P < 0.0001] in the entire study population. The association was significant in women [HR = 1.025 (1.013-1.037), P < 0.0001], but not in men [HR = 1.009 (0.998-1.019), P= 0.108]. After adjustment for Framingham risk score (FRS), SUA was no longer significant in the entire study population [HR = 1.006 (0.998-1.014), P= 0.122] or in men [HR = 1.006 (0.995-1.017), P= 0.291], but was significant in women [HR = 1.013 (1-1.025), P= 0.0457]. The baseline-to-end-of-study increase in SUA (standard deviation, SD) was greater (P < 0.0001) in atenolol-treated subjects (44.4 +/- 72.5 micromol/L) than in losartan-treated subjects (17.0 +/- 69.8 micromol/L). SUA as a time-varying covariate was strongly associated with events (P < 0.0001) in the entire population. The contribution of SUA to the treatment effect of losartan on the primary composite end point was 29% (14%-107%), P= 0.004. The association between time-varying SUA and increased CV risk tended to be stronger in women (P < 0.0001) than in men (P= 0.0658), although the gender-outcome interaction was not significant (P= 0.079). The increase in SUA over 4.8 years in the LIFE study was attenuated by losartan compared with atenolol treatment, appearing to explain 29% of the treatment effect on the primary composite end point. The association between SUA and events was stronger in women than in men with or without adjustment of FRS.