Dipstick Proteinuria and Reduced Estimated Glomerular Filtration Rate as Independent Risk Factors for Osteoporosis

Background: Osteoporosis is associated with a poor quality of life and mortality. Proteinuria contributes to vitamin D deficiency and osteoblast dysfunction. The correlation between estimated glomerular filtration rate (eGFR) and bone density still remains elusive. Therefore, we sought to investigate whether reduced eGFR or proteinuria are independently associated with the osteoporotic risk. Methods: We conducted a cross-sectional study using community-based health survey data from January 2004 to December 2008 in southern Taiwan. Positive proteinuria was defined as presence of 1+ or more urinary proteins on the dipstick. The bone density was measured by calcaneal quantitative ultrasound (QUS). Subjects with T-score ≤ −2.5 were considered as osteoporotic. Results: A total of 21,271 subjects of whom 11.3% had proteinuria were analyzed. Proteinuric participants were older, predominantly male, and more likely to have diabetes, hypertension, or exercise less regularly (P < 0.001). Multiple linear regression analysis showed that male sex, body mass index, regular exercise, eGFR and high density lipoprotein-cholesterol were positively correlated with QUS T-scores, whereas age, systolic blood pressure and proteinuria were negatively associated with QUS T-scores (P < 0.01). Compared with subjects in the highest eGFR tertile, those in the middle and the lowest groups had adjusted ORs for osteoporosis of 1.31 (95% CI: 1.20-1.44) and 2.46 (1.73-3.48), respectively. Additionally, the fully adjusted ORs of osteoporosis were 1.15 (1.02-1.32) and 1.18 (1.05-1.33) for participants with 1+ and ≥2+ proteinuria, respectively. Conclusions: Reduced eGFR and proteinuria are significantly associated with risk for osteoporosis.