Reduced Bone Mass Density Linked to Low Serum Bicarbonate

Association between serum bicarbonate levels and bone mineral density was stronger in women.
Association between serum bicarbonate levels and bone mineral density was stronger in women.

Low serum bicarbonate levels are associated with decreased bone mineral density (BMD) in U.S. adults, particularly postmenopausal women, according to findings published online ahead of print in the American Journal of Kidney Diseases.

Wei Chen, MD, of the University of Rochester School of Medicine and Dentistry in Rochester, N.Y., and colleagues at the Albert Einstein College of Medicine, Bronx, N.Y., studied 9,724 adults aged 20 years or older who participated in the National Health and Nutrition Examination Survey (NHANES) from 1999–2004. Women made up 48.8% of the study cohort.

Among women, each 2.2 mEq/L increment in serum bicarbonate level was associated with a significant 0.007 g/cm2 greater lumbar BMD and significant 0.005 g/cm2 greater total BMD. Using a serum bicarbonate level below 24 mEq/L as a reference value, women with serum bicarbonate levels of 27 mEq/L or higher had a significant 0.019 g/cm2 greater lumber BMD and a significant 0.018 g/cm2 greater total BMD compared with the reference group.

Additionally, compared to the reference group, women with a serum bicarbonate level of 27 mEq/L or higher had a 32% reduced odds of having low total bone mass, which was defined as 1.0 standard deviation below the mean value of young women in the cohort.

In a subgroup analysis of 2,805 pre- and post-menopausal women, the investigators found a significant association between serum bicarbonate levels and total BMD only in postmenopausal women. In this group, those with a serum bicarbonate level of 27 mEq/L or higher had 0.024 g/cm2 greater total BMD than those with a level below 24 mEq/L.

Among men, each 2.2 mEq/L increment in serum bicarbonate level was associated with a significant 0.008 g/cm2 increase in lumbar BMD and a non-significant 0.004 g/cm2 increase in total BMD.  Compared to the reference group (serum bicarbonate level below 24mEq/L), men with a serum bicarbonate level of 27 mEq/L or greater had a significant 0.019 g/cm2 greater lumbar BMD and a non-significant 0.012 g/cm2 greater total BMD compared with the reference group.

Dr. Chen's group noted that, for patients with chronic kidney disease, the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative guidelines suggest supplementing with alkali salts to maintain serum bicarbonate levels at 22 mEq/L or higher because bicarbonate supplements have been shown to improve skeletal metabolism in clinical studies.

Despite evidence for the beneficial effects of alkali therapy on bone health, alkali therapy still is not given routinely to individuals without kidney disease in the clinical setting to maintain bone mass, the authors stated. “Our study demonstrates that within a relatively normal range of serum bicarbonate levels, having higher serum bicarbonate levels is associated with higher BMD in the general population without advanced CKD,” the authors wrote. “These data give more support to providing alkali therapy in the general population for improvement of bone health.”

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