Cross-sectional associations between clinical biochemistry and nutritional biomarkers and sarcopenic indices of skeletal muscle in the Baltimore Longitudinal Study of Aging

Background: Investigating relationships between nutritional and clinical biochemistry biomarkers and skeletal muscle mass, strength and function (sarcopenic indices) may 1) highlight micronutrients of interest for potential preventive or treatment strategies for sarcopenia, or 2) highlight biomarkers that may be useful for identifying individuals at risk of sarcopenia. Objectives: Investigate associations between nutritional biomarkers (vitamin D, vitamin B ₁₂, folate, magnesium, potassium, calcium, and iron), clinical biomarkers (hemoglobin, ferritin, albumin, creatinine, and hemoglobin A1c: HbA1c), and sarcopenic indices (appendicular lean mass: ALM); height-adjusted ALM: ALM _ht; fat-free mass as a percentage of total body weight; extended short physical performance battery score: _extSPPB; height-adjusted hand grip strength: HGS _ht; height-adjusted knee extension concentric strength, and; height-adjusted knee extension isometric strength) in males and females. Methods: Using multivariable linear regression analysis, we investigated cross-sectional associations between biomarkers and sarcopenic indices in data collected from 1761 participants (age 22–103 y) from the Baltimore Longitudinal Study of Aging. Results: Hemoglobin was positively associated with ALM (β = 0.20, P = 0.021), HGS _ht (β = 0.25, P = 0.001), and _extSPPB (β = 0.13, P = 0.024) in males, and with _extSPPB in females (β = 0.15, P = 0.019). In males, serum iron was positively associated with ALM _ht (β = 0.0021, P = 0.038) and _extSPPB (β = 0.0043, P = 0.045). In females, ferritin was positively associated with knee-extension strength measurements. Serum creatinine was positively associated with lean mass measures in males and females and with muscle strength and function measures in males with normal renal function (estimated glomerular filtration rate ≥60 mL/min/1.73 m ²). In males, high HbA1c was associated with lower ALM _ht (β = –0.21, P = 0.023), _extSPPB (β = –0.40, P = 0.027), and HGS _ht (β = –0.56, P = 0.031). In males and females, magnesium was positively associated with _extSPPB, and potassium was positively associated with measures of knee-extension strength. Conclusions: The associations found between measures of iron status and creatinine and sarcopenic indices, in males in particular, indicate potential importance for muscle health. Future longitudinal and intervention studies are warranted to confirm these findings.