Relationship between eosinophils counts and muscle mass decline in older people with type 2 diabetes: A prospective study of the KAMOGAWA-DM cohort

Sarcopenia has become an important issue in older individuals with type 2 diabetes. However, no previous studies investigated the relationship between eosinophil count and muscle mass decline. In this prospective cohort study, we aimed to investigate this relationship in older people with type 2 diabetes. Impedance body composition was used to assess body composition and skeletal muscle mass index (SMI, kg/m2) was calculated as appendicular muscle mass (kg)/height squared (m2). The decrease in SMI (kg/m2 per year) was calculated as (baseline SMI [kg/m2] - follow-up SMI [kg/m2]) divided by the follow-up period (years). The rate of SMI decrease (%) was calculated as follows: (decrease in SMI [kg/m2 per year] ÷ baseline SMI [kg/m2]) × 100; muscle mass decline was defined as the rate of SMI decrease of ≥0.5%. Complete blood counts, including eosinophil counts, were also measured. Among 141 participants, 54.6% experienced muscle mass decline during mean (standard deviation)19.4 (7.3) months of follow-up. The eosinophil counts of participants with muscle mass decline were higher than those of participants without muscle mass decline (216.5 [147.8] vs. 158.6 [113.1] cells/mm3, p = 0.004). Eosinophil counts were negatively associated with the rate of SMI decrease according to Spearman's rank correlation coefficient (r = 0.182, p = 0.031). According to logistic regression analyses, there was the relationship between eosinophil counts and incident muscle mass decline after adjusting for covariates (odds ratio of Δ 1 incremental of logarithm (eosinophil counts) 2.04 (95% confidence interval 1.15-3.61, p = 0.011). This study showed that eosinophil counts are associated with incident muscle mass decline. If an individual with type 2 diabetes has high eosinophil counts in blood tests, then it is necessary to pay more attention to the possibility of progression of muscle atrophy.