Haemoglobin shares nonlinear correlation with bone mineral density

There appears to be a significant but nonlinear association between haemoglobin levels and bone mineral density (BMD) at the lumbar and thoracic spine, a recent study has found.

The researchers conducted a cross-sectional analysis, enrolling 8,491 noninstitutionalized adults whose data were retrieved from the National Health and Nutrition Survey. Multivariate linear regression analysis revealed a significant and negative correlation between haemoglobin and lumbar spine BMD (β, –0.0416; p=0.031873).

Complete adjustment for covariates, however, attenuated this interaction for thoracic spine BMD (β, –0.0127; p=0.362458).

However, to explore a potential nonlinear association between the variables, the researchers performed smooth curve fitting, which indeed showed such an interaction.

Among Asian participants, BMD in the thoracic spine decreased along with decreasing haemoglobin until the turning point of 14.9 g/dL, after which BMD showed an upward trend. A similar pattern was reported for bone mineral density which decreased with haemoglobin until the inflection point of 13.4 g/dL. This U-shaped relationship was also observed for other races.

“The U-shaped curve in the relationship between haemoglobin and BMD in the Non-Hispanic Asian population implies that BMD in the thoracic and lumbar spine may be quietly decreasing as haemoglobin levels approach” the inflection point, the researchers said.

“Clinicians should be aware of low levels of haemoglobin while being alert to the risk of reduced bone mass and the need for close monitoring of BMD and early intervention,” they added.

Further studies are warranted to explain the mechanisms underlying this association, according to the researchers.