Objective: To evaluate the association between BMI levels, muscular strength, muscle composition and physical performance, in a follow-up of 6 years, in an elderly population.
Materials and Methods: 2911 Italians subjects aged > 65 years from the Progetto Veneto Anziani (ProVA) study were analyzed. ProVA was a population study focused on chronic diseases and functional limitations. Physical performance with the Short Physical Performance Battery (SPPB) and leg muscular strength with dynamometry were measured in all subjects both at baseline and at the end of follow-up.. Fat distribution and skeletal muscle composition were measured in an abdominal single-scan magnetic resonance (MRI) in a randomly selected sample of 348 subjects at baseline. Study population was stratified by six BMI classes: underweight (BMI<18.5 kg/m2), normal weight (BMI 18.5-24.9), overweight (BMI 25.0-29.9), obesity I level (30.0-34.9), obesity II level (35.0-39.9), and severe obesity (BMI≥40.0). Associations between BMI levels, muscular strength, muscle compositions and physical performance were analyzed in multivariable adjusted models.
Results: In the ProVA population, an association between BMI levels and SPPB was observed. Normal weight subjects showed, in a sex and age-adjusted model, the best SPPB scores (8.29±0.03), with significant differences compared to underweight (7.50±0.15; p<0.001), overweight (8.12±0.02; p<0.001), class I (7.72±0.04; p<0.001), class II (6.67±0.09; p<0.001) and class III obesity (5.88±0.24; p<0.001). This pattern was not modified by further adjustment for socio-economic status, smoke, physical activity level and comorbidities. Compared to normal weight subjects (22.9±0.1 kg), leg muscular strength was higher in overweight (23.8±0.1; p<0.001) and in class I obesity (24.5±0.1; p<0.001), but it was reduced in class II (21.4±0.3; p<0.001) and class III obesity (19.8±0.9; p<0.001). The association between BMI and impaired physical performance was not significantly affected by adjustment for leg muscular strength. In a multiple logistic analysis, performed after the exclusion of subjects with at the baseline value <3 in the SPPB test, and adjusting for age, sex, smoking, income, education, physical activity and chronic disease, a significant increased risk of a statistically significant reduction in SPPB test was observed for overweight and obese subjects.
In the subgroup of patients with abdominal MRI, at the baseline, an inverse association between SPPB scores and the degree of fat infiltration of skeletal muscle was observed.
Conclusion: A poor physical performance was observed in overweight and obese elderly subjects, whereas leg muscular strength was reduced only in subjects with more severe obesity. The physical performance was negatively influenced by the degree of fat infiltration in skeletal muscle. Moreover, an increased risk of worsening in physical performance during the years was found in overweight and obese as compared to normal weight subjects. In conclusion high BMI values affect negatively physical performance and expose the elderly to a risk of a further decline in physical performance with consequent disabilit
