Frailty syndrome and skeletal muscle: results from the Invecchiare in Chianti study

Abstract

Background: Frailty is a common condition in elders and identifies a state of vulnerability for adverse health outcomes.

Objective: Our objective was to provide a biological face validity to the well-established definition of frailty proposed by Fried et al.

Design: Data are from the baseline evaluation of 923 participants aged > or =65 y enrolled in the Invecchiare in Chianti study. Frailty was defined by the presence of > or =3 of the following criteria: weight loss, exhaustion, low walking speed, low hand grip strength, and physical inactivity. Muscle density and the ratios of muscle area and fat area to total calf area were measured by using a peripheral quantitative computerized tomography (pQCT) scan. Analyses of covariance and logistic regressions were performed to evaluate the relations between frailty and pQCT measures.

Results: The mean age (+/-SD) of the study sample was 74.8 +/- 6.8 y, and 81 participants (8.8%) had > or =3 frailty criteria. Participants with no frailty criteria had significantly higher muscle density (71.1 mg/cm(3), SE = 0.2) and muscle area (71.2%, SE = 0.4) than did frail participants (69.8 mg/cm(3), SE = 0.4; and 68.7%, SE = 1.1, respectively). Fat area was significantly higher in frail participants (22.0%, SE = 0.9) than in participants with no frailty criteria (20.3%, SE = 0.4). Physical inactivity and low walking speed were the frailty criteria that showed the strongest associations with pQCT measures.

Conclusion: Frail subjects, identified by an easy and inexpensive frailty score, have lower muscle density and muscle mass and higher fat mass than do nonfrail persons.

Figure 1

Differences in muscle density, muscle area ratio, and fat area ratio (obtained by peripheral quantitative computerized tomography scans) according frailty syndrome status (dependent variable). The differences were analyzed with an analysis of covariance adjusted for age, sex, Mini Mental State Examination score, myocardial infarction, congestive heart failure, hypertension, osteoarthritis, peripheral artery disease, stroke, and concentrations of albumin, hemoglobin, interleukin 6, C-reactive protein, and tumor necrosis factor α (log values). Intermediate frailty was defined as having 1 or 2 frailty criteria, and frailty was defined as having ≥3 frailty criteria. Values are expressed as adjusted means and 95% CIs. P for trend = 0.01 for muscle density, 0.004 for muscle area ratio, and 0.005 for fat area ratio.