Decreasing levels of vitamin D are associated with increases in the prevalence in albuminuria, according to an epidemiologic study.
Ian H. de Boer, MD, MS, of the University of Washington in Seattle, and his colleagues examined data from 15,068 adults who participated in the Third National Health and Nutrition Examination Survey, a large representative sample of the U.S. population.
All underwent measurement of serum 25-hydroxyvitamin D and urine albumin and creatinine. Circulating 25-hydroxyvitamin D levels reflect total intake of vitamin D from dietary and cutaneous sources, Dr. Boer’s team noted. Subjects were divided into vitamin D quartiles: 3.5-17.6, 17.7-24.1, 24.2-32.0, and 32.0-97.6 ng/mL (reference).
The study population had a mean 25-hydroxyvitamin D level of 29.5 ng/mL and an overall prevalence of albuminuria of 11.6%. The prevalence of micro- and macroalbuminuria was 10.6% and 1.0%, respectively.
With decreasing quartiles of vitamin D level, the prevalence of albuminuria—either micro- or macroalbuminuria—was 8.9%, 11.5%, 13.7%, and 15.8%, the researchers reported in the American Journal of Kidney Diseases (2007;50:69-77). Each quartile of decreasing vitamin D level was associated with a 4.8% greater mean ACR. The researchers defined albuminuria as a urine albumin-creatinine ratio (ACR) of 25-2,999 mg/g for women and 17 to 2,999 mg/g for men.
Compared with reference vitamin D levels, levels of 24.2-32.0, 17.7-24.1, and 3.5-17.6 ng/mL were associated with a 12%, 22%, and 31% increased risk of albuminuria, respectively, after adjusting for age, sex, race and ethnicity, region of the United States, season, smoking status, BMI, estimated glomerular filtration rate (GFR), BP, and diabetes.