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: (i) highlight micronutrients of interest for potential preventive or treatment strategies for sarcopenia, or (ii) highlight biomarkers that may be useful for identifying individuals at risk of sarcopenia.

Objectives: Investigate associations between nutritional biomarkers (vitamin D, vitamin B12, folate, magnesium, potassium, calcium, iron), clinical biomarkers (haemoglobin, ferritin, albumin, creatinine, HbA1c) and sarcopenic indices (appendicular lean mass (ALM), height-adjusted ALM (ALM), fat-free mass percentage of body weight (FFM%), extended short physical performance battery score (SPPB), and height-adjusted hand grip strength (HGS) and knee extension concentric (KEC) and isometric (KEI) strength) in men and women.

Design: Using multivariable linear regression analysis we investigated cross-sectional associations between biomarkers and sarcopenic indices in data collected from 1,761 participants (age 22-103 years) from the Baltimore Longitudinal Study of Aging (BLSA).

Results: Haemoglobin was positively associated with ALM (β=0.20, p=0.021), HGS (β=0.25, p=0.001) and SPPB (β=0.13, p=0.024) in men, and with SPPB in women (β=0.15, p=0.019). In men, serum iron was positively associated with ALM (β=0.0021, p=0.038) and SPPB (β=0.0043, p=0.045). In women, ferritin was positively associated with knee-extension strength measurements. Serum creatinine was positively associated with lean mass measures in men and women, and with muscle strength and function measures in men with normal renal function (estimated glomerular filtration rate 60 mL/min/1.73m). In men, high HbA1c was associated with lower ALM (β=-0.21, p=0.023), SPPB (β=-0.40, p=0.027) and HGS (β=-0.56, p=0.031). In men and women, magnesium was positively associated with SPPB, and potassium was positively associated with measures of knee-extension strength.

Conclusion: The associations found between measures of iron status and creatinine and sarcopenic indices, in men in particular, indicate potential importance for muscle health. Future longitudinal and intervention studies are warranted to confirm these findings.