Sarcopenia, sarcopenic obesity, and functional impairments in older adults: National Health and Nutrition Examination Surveys 1999-2004

Abstract

The Foundation for the National Institutes of Health Sarcopenia Project validated cutpoints for appendicular lean mass (ALM) to identify individuals with functional impairment. We hypothesized that the prevalence of sarcopenia and sarcopenic obesity would be similar based on the different Foundation for the National Institutes of Health criteria, increase with age, and be associated with risk of impairment limitations. We identified 4984 subjects at least 60 years of age from the National Health and Nutrition Examination Surveys 1999-2004. Sarcopenia was defined using ALM (men <19.75 kg, women <15.02 kg) and ALM adjusted for body mass index (BMI; men <0.789 kg/m², women <0.512 kg/m²). Sarcopenic obesity is defined as subjects fulfilling the criteria for sarcopenia and obesity by body fat (men ≥25%, women ≥35%). Prevalence rates of both sarcopenia and sarcopenic obesity were evaluated with respect to sex, age category (60-69, 70-79, and >80 years) and race. We assessed the association of physical limitations, basic and instrumental activities of daily living and sarcopenia status. The mean age was 70.5 years in men and 71.6 years in women. Half (50.8%; n = 2531) were female, and mean BMI was 28 kg/m² in both sexes. Appendicular lean mass was higher in men than in women (24.1 vs 16.3; P < .001), but fat mass was lower (30.9 vs 42.0; P < .001). In men, sarcopenia prevalence was 16.0% and 27.8% using the ALM and ALM/BMI criteria. In women, prevalence was 40.5% and 19.3% using the ALM and ALM/BMI criteria. Sarcopenia was associated with a 1.10 (0.86-1.41) and 0.93 (0.74-1.16), and 1.46 (1.10-1.94), and 2.13 (1.41-3.20) risk of physical limitations using the ALM and ALM/BMI definitions in men and women, respectively. Prevalence of sarcopenia and sarcopenic obesity varies greatly, and a uniform definition is needed to identify and characterize these high-risk populations.

Introduction

One of the unfortunate consequences of people living longer [1] is the greater incidence of functional impairment and disability [2]. Impaired function in older adults is associated with a higher risk of institutionalization, mortality, and a compromised quality of life [3], [4], [5]. Sarcopenia, defined as the loss of muscle mass and strength with aging, is a strong predictor of adverse outcomes [6]. This syndrome is commonly observed in geriatrics practices and is increasingly recognized as an entity, even in surgical subspecialties [7].

Identifying patients with sarcopenia is critically important in order to target interventions for older adults who are at greatest risk. The standardized definition of sarcopenia varies throughout the literature [8]. Variation occurs because multiple mathematical constructs of the condition have been developed using different age cutoffs or on lower quintiles of a cohort being examined. Racial and ethnic differences in study and referent populations may also contribute to the variation in the prevalence. This creates an inherent challenge in applying cutoffs to populations that may have different characteristics than the one being examined.

The Foundation for the National Institutes of Health (FNIH) in 2014 was developed on the premise that clinically relevant cutpoints are associated with longitudinal adverse outcomes [9]. Based on large cohort studies, this group recognized both muscle strength (as represented by grip strength) and muscle mass as 2 important determinants of future function. The purpose of our study was to apply the definitions from the FNIH consortium on a representative cohort of older adults to ascertain the prevalence of sarcopenia and sarcopenic obesity. We hypothesized that the 2 FNIH definitions of sarcopenia based on muscle mass would provide similar prevalence estimates of sarcopenia and sarcopenic obesity, increase with age, and be associated with functional impairments.