Psychometric and biological aspects of frailty and muscle mass in community-dwelling older adults: Results from the PRO-EVA study
frailty; muscle, skeletal; reference values; decision trees; biomarkers.
Introduction: Frailty is a biological syndrome characterized by an increase in physical and psychological vulnerability and reduced resistance to stressors, physiological reserves and intrinsic capacity of an individual. The development of this condition seems to be, in parts, associated with the biological mechanisms involved in the aging process, making it essential to better understand these mechanisms. Frailty is widely associated with decreased body muscle mass, which has physical and social consequences for the older adults. The use of low-cost and easily applicable instruments and models for screening for frailty and low muscle mass in the older adults is feasible in primary health care, since their diagnoses are complex and require the use of high-cost technologies. Aim: To understand the biological aspects of frailty and low muscle mass, in addition to enabling the screening of both conditions through psychometric measures. Methods: This thesis presents a narrative review and two cross-sectional studies composed of 786 community-dwelling older adults residents in Parnamirim (Rio Grande do Norte), aged 60 or over. Sociodemographic, anthropometric, body composition and physical performance data were assessed. Short Physical Performance Battery (SPPB) diagnostic accuracy was evaluated for frailty and pre-frailty screening. For the screening of low muscle mass, analyzes were performed with a regression tree to identify a model. For the narrative review, information was gathered about the association between biomarkers of the aging phenotype proposed by López-Otín et al. (2013) and frailty. Results: SPPB has good diagnostic accuracy to discriminate between non-frail and frail older adults using a cut-off point of ≤9 points. For the identification of pre-frailty, SPPB presented measures of diagnostic accuracy from low to moderate, however, it was verified that this instrument can help in screening pre-frail older adults from the cut-off point of ≤11 points in total SPPB score. For the screening of low muscle mass, an algorithm with high accuracy was developed based on the factors of Body Mass Index (BMI) (values ≤ 22.7 kg/m² for men and ≤ 24.9 kg/m² for women), sex (female), calf circumference (values ≤ 31.7 cm for women with a BMI ≤ 24.9 kg/m²) and use of psychotropic drugs in individuals with a BMI > 29.4 kg/m². Regarding the narrative review, the main biomarkers of aging associated with frailty were identified: mitochondrial DNA (mtDNA) copy number, telomere length, global DNA methylation, Hsp70, Hsp72, IGF-1, SIRT1, GDF-15, CD4+ and CD8+ cell percentages, circulating osteogenic progenitor cells, IL-6, CRP and TNF-alpha. Conclusions: The identification of frailty is possible through the SPPB, since it has good diagnostic accuracy to discriminate between non-frail and frail older people using a cut-off point of 9 points in the total score, being better to identify those non-frail individuals. Although the SPPB's diagnostic accuracy in detecting pre-frailty was moderate to low, this instrument can help in the screening of these older adults, allowing the implementation of early interventions. The screening of low muscle mass can be possible using the developed algorithm in this study, which showed high accuracy, based on the factors of BMI, sex, calf circumference and use of psychotropic drugs. Finally, among the main biomarkers of aging associated with frailty, IGF-1, SIRT1, GDF-15, IL-6, CRP and TNF-alpha presented more robust evidence, highlighting the importance of inflammation and nutrient sensing on frailty.