Relationship between serum cystatin C and hypertension among US adults without clinically recognized chronic kidney disease.

Previous animal studies have suggested that mild reductions in renal function, even before the development of clinically recognized chronic kidney disease (CKD), are associated with hypertension. However, few studies have examined this hypothesis in humans. We therefore examined the association between serum cystatin C levels and hypertension among subjects without clinically recognized CKD in a large multiethnic sample of US adults. We examined the National Health and Nutrition Examination Survey 1999-2002 participants >20 years of age (n = 2583, 54.5% women) without clinically recognized CKD (defined as an estimated glomerular filtration rate <60 mL/min/1.73 m(2) or microalbuminuria). Serum cystatin C levels were categorized into quartiles (<0.76 mg/L, 0.76-0.86 mg/L, 0.87-0.97 mg/L, and >0.97 mg/L). Hypertension was defined as blood pressure (BP)-reducing medication use or having systolic BP ≥ 140 mm Hg and/or diastolic BP ≥ 90 mm Hg. Higher serum cystatin C levels were found to be associated with hypertension in women, but not men. After adjusting for age, race-ethnicity, education, smoking, alcohol intake, body mass index, diabetes, total cholesterol and C-reactive protein, the odds ratio (95% confidence interval) of hypertension comparing quartile 4 of cystatin C to quartile 1 (referent) was 2.04 (1.13-3.69); P trend = .02 in women and 0.86 (0.53-1.41); P trend = .51 in men. In a representative sample of US adults, mild reductions in kidney function as measured by higher serum cystatin C levels among subjects without clinically recognized CKD are associated with hypertension in women, but not men.