Insulin-Like Growth Factor-1 (IGF-1) and Reduced Tongue Pressure in Relation to Atherosclerosis Among Community-Dwelling Elderly Japanese Men: A Cross-Sectional Study

Even though higher serum insulin-like growth factor-1 (IGF-1) levels have a positive effect on preventing reduction in muscle strength, a U-shaped association between IGF-1 and mortality has been reported. Since a recent experimental study revealed that IGF-1 is associated with atherosclerotic lesion formation, the inflammatory status of atherosclerosis could act as a confounding factor on the association between IGF-1 levels and reduced muscle strength. This study aimed to clarify the atherosclerosis-specific association between IGF-1 levels and reduced muscle strength. We conducted a cross-sectional study of 410 elderly men aged 60-89 years. Since a reduction in maximum voluntary tongue pressure against the palate (MTP) is reportedly associated with sarcopenia, we evaluated muscle strength by using MTP and defined reduced MTP as the lowest tertiles of the study population. Among study population, 295 showed no atherosclerosis (carotid intima-media thickness < 1.1 mm). Even though a significant inverse association between IGF-1 and reduced MTP was observed for subjects without atherosclerosis, no such association was detected for subjects with atherosclerosis. The known cardiovascular risk-factor adjusted odds ratio (OR) of a one-standard deviation (SD) increment (28.1 ng/mL) of IGF-1 for reduced MTP was 0.69 (0.51, 0.95) for subjects without atherosclerosis and 1.93 (1.05, 3.52) for subjects with atherosclerosis. IGF-1 was found to be inversely associated with a reduced MTP among elderly men without atherosclerosis but not among those with atherosclerosis. Atherosclerosis can thus act as a powerful confounding factor on the association between IGF-1 levels and a reduced MTP.