Serum bicarbonate concentration is associated with bone density in adults with type 2 diabetes mellitus: African American-Diabetes Heart Study.

BACKGROUND: Osteoporosis is a significant cause of morbidity and mortality in the aging population. Individuals with type 2 diabetes mellitus (T2D) typically have higher bone density yet also a higher rate of fractures. Blacks, meanwhile, have a lower incidence of osteoporosis compared to European Americans. Serum bicarbonate may be a risk factor for bone loss, but studies are conflicting, and little is known about this relationship in T2D or Blacks. METHODS: We examined the longitudinal relationship between serum bicarbonate and change in bone density in 300 participants with T2D in the African American-Diabetes Heart Study (AA-DHS). Serum bicarbonate was measured at baseline, and bone density was assessed using CT volumetric bone mineral density (vBMD) scans of the thoracic and lumbar vertebrae at baseline and after five years of follow-up. Multivariate linear regression models assessed associations between baseline serum bicarbonate and longitudinal change in vBMD, adjusted for multiple confounders. RESULTS: The cohort was 50 % female, with mean age and T2D duration 55.1 years and 10.2 years, respectively. The mean baseline serum bicarbonate was 26.6 (SD 3.3) mEq/L; median baseline lumbar spine vBMD 179.3 (IQR 148.2, 208.9) mg/cm(3), and median baseline thoracic spine vBMD 204.9 (IQR 171.6, 231.9) mg/cm(3). In fully-adjusted analyses, each 1 mEq/L increase in baseline serum bicarbonate was significantly associated with 5-year relative increase in lumbar vBMD (0.94 mg/cm(3), p < 0.001) and thoracic vBMD (1.35 mg/cm(3), p < 0.001), without a clear threshold effect or differences by sex. CONCLUSIONS: In this cohort of Blacks with T2D, higher baseline serum bicarbonate levels were associated with improved changes in bone density over time. Further studies are needed to determine if alkali supplementation would ameliorate loss of bone density in this population.