Chapter 5 The association between parameters of malnutrition and diagnostic measures of sarcopenia in geriatric outpatients

Background: Diagnostic criteria for sarcopenia include measures of muscle mass, muscle strength and physical performance. Consensus on the definition of sarcopenia has not been reached yet. To improve insight into the most clinically valid definition of sarcopenia, this study aimed to compare the association between parameters of malnutrition, as a risk factor in sarcopenia, and diagnostic measures of sarcopenia in geriatric outpatients. Methods: This study is based on data from a cross-sectional study conducted in a geriatric outpatient clinic including 185 geriatric outpatients (mean age 82 years). Parameters of malnutrition included risk of malnutrition (assessed by the Short Nutritional Assessment Questionnaire), loss of appetite, unintentional weight loss and underweight (body mass index <22 kg/m). Diagnostic measures of sarcopenia included relative muscle mass (lean mass and appendicular lean mass (ALM) as percentages), absolute muscle mass (total lean mass and ALM/height), handgrip strength and walking speed. All diagnostic measures of sarcopenia were standardized. Associations between parameters of malnutrition (independent variables) and diagnostic measures of sarcopenia (dependent variables) were analysed using multivariate linear regression models adjusted for age, body mass, fat mass and height in separate models. Results: None of the parameters of malnutrition was consistently associated with diagnostic measures of sarcopenia. The strongest associations were found for both relative and absolute muscle mass; less stronger associations were found for muscle strength and physical performance. Underweight (p=<0.001) and unintentional weight loss (p=0.031) were most strongly associated with higher lean mass percentage after adjusting for age. Loss of appetite (p=0.003) and underweight (p=0.021) were most strongly associated with lower total lean mass after adjusting for age and fat mass. Conclusion: Parameters of malnutrition relate differently to diagnostic measures of sarcopenia in geriatric outpatients. The association between parameters of malnutrition and diagnostic measures of sarcopenia was strongest for both relative and absolute muscle mass, while less strong associations were found with muscle strength and physical performance. Introduction Sarcopenia is a frequent syndrome in older persons, leading to functional limitations and metabolic dysregulation [1, 2]. Its clinical relevance is increasingly being recognized. The term sarcopenia literally means the ‘deficiency’ (penia) of ‘flesh’ (sarx) and was introduced in 1989 by Rosenberg [3]. Since then, several diagnostic criteria have been proposed [4]. These criteria consist of different combinations of measures of relative and absolute muscle mass, muscle strength and physical performance and different cut-off points with respect to different reference populations. Consensus working groups proposed to define sarcopenia as a syndrome characterized by the age-related loss of muscle mass and loss of muscle function, including muscle mass and strength and/or physical performance [5-10]. However, this consensus is still under debate. Relating different measures of sarcopenia with different clinical syndromes is required to establish the most clinically valid definition. The definition of sarcopenia should be based on those diagnostic measures of sarcopenia that associate most strongly with muscle-related outcomes. In previous studies, a stronger association was reported between relative muscle mass and physical performance and glucose regulation, compared to absolute muscle mass, muscle strength and physical performance [11, 12]. In contrast, a stronger association was reported between absolute muscle mass and bone mineral density [13]. Another clinically relevant syndrome is body protein stock in relation to nutritional status [14]. Malnutrition is prevalent in approximately 20 percent of the geriatric outpatients, while more than half of these outpatients are at risk of malnutrition [15]. Malnourished older persons have an increased risk of sarcopenia due to reduced muscle protein synthesis [14]. In addition, low dietary protein intake is associated with a higher loss of lean mass in community-dwelling older persons [16]. Malnutrition and sarcopenia are both of important clinical relevance and interrelated in their pathophysiology. Exploring how parameters of malnutrition relate to diagnostic measures of sarcopenia adds insight in the most valid clinical definition of sarcopenia. This study aimed to compare the association between parameters of malnutrition, comprising risk of malnutrition, loss of appetite, unintentional weight loss and underweight, and different diagnostic measures of sarcopenia (relative and absolute muscle mass, muscle strength and physical performance) in a clinically relevant geriatric outpatient population. 44654 Esmee Reijnierse.indd 72 20-02-17 15:13 Diagnostic measures of sarcopenia and parameters of malnutrition