Anew study from China suggests, a decline in kidney function may be an independent risk factor for lower lumbar spine bone mineral density ( LBMD ) as healthy Chinese postmenopausal women age. The study was punctuated in the journal  Menopause , both the estimated glomerular filtration rate (eGFR) and LBMD progressively declined with age.

Dr. Kristi Tough DeSapri, a clinical assistant professor of obstetrics and gynecology at the University of Chicago said, "After controlling for multiple variables, a significant positive association between GFR and lumbar spine BMD (and T-score) was seen."

"Both chronic kidney disease and osteopenia / osteoporosis are underdiagnosed and undertreated conditions." This cross-sectional study that evaluated the correlation between decline in kidney function and decline in bone mineral density highlights how both conditions are, "added Dr. Tough DeSapri.

Dr. Xiang-Mei Chen, of the Department of Nephrology of General Hospital of Chinese People's Liberation Army in Beijing, and colleagues conducted a community-based cross-sectional study of 390 healthy postmenopausal women (mean age, 63) from Shenyang, China .

The measured LBMD using dual-energy X-ray absorptiometry, and they calculated eGFR using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation modified for Asians, as well as the CKD-EPI serum creatinine-cystatin C equation.

The eGFR-ASIA and eGFR-Scys (serum creatinine) correlated positively with LBMD after adjustments for potential demographic, clinical, and behavioral confounders. Specifically, women in the third quarter of eGFR-ASIA had significantly higher odds for age-related LBMD decline (odds ratio, 2.45).

The OR for women in the fourth eGFR-ASIA quartile was 3.89. Women in the first quartile served as the reference group for these comparisons. In addition, women in the third and fourth quartiles of eGFR-Scys had significantly higher ORs for LBMD decline (2.47 and 2.63, respectively), compared with women in the first quartile.

Researchers know that patients with chronic kidney disease have many reasons to have bone loss (secondary hyperparathyroidism, vitamin deficiency, etc.). However, using the CKD-EPI – versus the more traditional Cockcroft-Gault (CG) or Modification of Diet in Renal Disease (MDRD) equations – to calculate GFR.

This study reported that lower GFRs correlated with lower spine BMD. CKD-EPI is a calculation that uses serum creatinine and the protein cystatin C to better capture kidney function

Since this study evaluated spine BMD only, if it is unknown, if hip, wrist, and forearm would show the same associations, particularly given that the spine is mostly trabecular bone and the long bones are stronger cortical bone .