Bryson CL (Northwest Center for Outcomes Research in Older Adults, Seattle; Dept. of Medicine, University of Washington)
Boyko EJ (VA Epidemiology Resource and Information Center, Seattle; Dept. of Medicine, University of Washington)
Ross BS (VA Epidemiology Resource and Information Center, Seattle)
Fihn SD (Northwest Center for Outcomes Research in Older Adults, Seattle;Dept. of Medicine, University of Washington)
Young BA (VA Epidemiology Resource and Information Center, Seattle; Dept. of Medicine, University of Washington)
Cadmium is a known environmental pollutant and renal tubular toxin for which occupational and dietary exposure are the main routes of human exposure. Urinary cadmium levels indicate cumulative levels of cadmium exposure, however, little data exist in which population-based associations of cumulative cadmium exposure, renal insufficiency, hypertension and microalbuminuria have been determined in US populations. We sought to determine whether elevated levels of urine cadmium are associated with microalbuminuria, systolic hypertension, and renal dysfunction.
Cross-sectional analyses were performed on data collected on 16,094 subjects participating in the Third National Health and Nutritional Examination Survey (NHANES III), a national complex sample survey. Subjects underwent extensive laboratory and physical examinations in addition to providing detailed health histories. Main outcome measures included prevalent systolic hypertension, microalbuminuria and chronic renal disease. Linear and logistic regression were used to assess associations and adjust for potential confounding while accounting for the complex sample design.
Elevated urine cadmium levels were associated with prevalent microalbuminuria, systolic hypertension and decreased calculated creatinine clearance after adjustment for age, sex, race, smoking, and use of diuretics. For those with urine cadmium levels greater than10 ng/mg of creatinine, creatinine clearance was lowered by 12 ml/min (95% CI=-14, -9), while systolic blood pressure was elevated by 36 mmHg (95% CI=22, 50), and urinary albuminuria levels were elevated by 9.8 ug/mg creatinine (95% CI=7.2, 13.4). When the odds of microalbuminuria were assessed by logistic regression, those subjects with mild elevations in urinary cadmium had a 28% greater odds of microalbuminuria (OR=1.28; 95% CI=1.06, 1.54), while those with the highest levels of urinary cadmium had 127-fold greater odds of microalbuminuria (OR=127.4; 95% CI=11.5, 1407.1) compared to those with normal urinary cadmium levels.
Elevated levels of urine cadmium are associated with reduced renal function, a higher prevalence of microalbuminuria and elevated systolic blood pressure.
Cadmium exposure may cause graded renal dysfunction at lower levels than previously established.