ABSTRACT
BACKGROUND: there is no longitudinal evidence about the association between the loss of total appendicular skeletal muscle (TASM) and cytokines. OBJECTIVE: to investigate whether high levels of the inflammatory markers such as interleukin-6 (IL-6) and C-reactive protein (CRP) are associated with the loss of TASM in free-living non-sarcopenic older people. DESIGN: five-year prospective cohort study. SUBJECTS: one hundred and fifteen free-living non-sarcopenic older men and women aged 60-84 years at baseline and 5-year follow-up were included. METHODS: TASM was measured by dual-energy X-ray absorptiometry, and the relative change in TASM was calculated. The response variable was the loss of TASM defined as the lowest sex-specific 15th percentile of the cohort distribution of percentage of change in TASM. The exposure variables were the baseline serum IL-6 and CRP levels measured by ELISA. RESULTS: sixteen subjects were below the sex-specific 15th percentile of the cohort. The mean absolute loss of TASM in these men and women subjects was 1.9 and 1.3 kg, respectively. The risk of loss TASM was 1.29 times higher (95% confidence interval [CI], 1.01-1.64) (P = 0.03) per unit of increase in IL-6 (pg/ml) and 1.28 times higher (95% CI, 1.04-1.58) (P = 0.01) per unit of increase in CRP (mg/l). As a categorical variable, the risk of loss TASM was 4.85 times higher (95% CI, 1.24-18.97) among subjects with serum IL-6 >2.71 pg/ml and 3.97 times higher (CI 95%, 1.09-14.39) among subjects with serum CRP >3.74 mg/l. These findings remained after adjusting for age, sex and 5-year weight change. CONCLUSIONS: inflammation is associated with the loss of TASM in free-living non-sarcopenic older men and women.
Subject(s)
Aging/immunology , C-Reactive Protein/metabolism , Inflammation Mediators/blood , Inflammation/immunology , Interleukin-6/blood , Muscle, Skeletal/pathology , Absorptiometry, Photon , Age Factors , Aged , Aged, 80 and over , Aging/pathology , Biomarkers/blood , Chi-Square Distribution , Enzyme-Linked Immunosorbent Assay , Female , Humans , Independent Living , Inflammation/diagnostic imaging , Inflammation/pathology , Logistic Models , Male , Mexico , Middle Aged , Muscle, Skeletal/diagnostic imaging , Organ Size , Prospective Studies , Time FactorsABSTRACT
Thirty four subjects (13 men and 21 women), 24 to 70 years old from northern Mexico, were measured for body density by air displacement plethysmography (ADP) with the BOD-POD, and for total body water by deuterium oxide dilution and infrared spectroscopy (IRS-DOD). Subjects were given a 30 g dose of deuterium oxide. Saliva samples were filtered, sublimated, and deuterium was measured using a Miran 1 FF, IRS. Linear regression of the fat mass (FM) derived from both methods showed that the intercept (0.071) was not different from zero (p = .96) and the slope was 0.96 (p < .0001) demonstrating the techniques to be equivalent. Further, mean FM was 26.7 +/- 12.4 and 25.6 +/- 12.4 kg, for IRS-DOD and ADP techniques, respectively (p = .08). Precision analysis by the model R2 showed that 92.3% of the variability was explained (SEM = 3.4 kg). Bland-Altman analysis showed no significant bias (r = 0.017; p = .93). Mean difference between methods was -1.08 (CI: -2.3 to + 0.13) kg FM.
