Phenotyping Anorexia of Ageing: A Survey to Categorise Appetite Loss in Older Adults

Anorexia of ageing, or appetite loss in older people, is thought to be influenced by three main categories of factors: (i) Physiology (changes in appetite signalling including changes to gut hormones, basal metabolic rate and gut motility), (ii) Pleasure of Eating (diminished sensory perception and reward processing) and (iii) External Cues (socioenvironmental changes such as isolation and loneliness). These are outside of secondary anorexia from a medical cause (such as cancer, etc). We argue that there may be two major phenotypes of anorexia of ageing that may be able to be distinguished behaviourally, and by having a tool to recognise the phenotype may lead to different clinical guidance and a more targeted clinical approach. The hypothesis is that the two types are: Type 1: the effect of the ageing gut on capacity to accommodate and digest food (i.e., early fullness), and Type 2: a ‘top down’ low desire to eat (reduced food reward) related to chronic/acute inflammation (not necessarily involving inflammation of the gut). These Type 1 and Type 2 causes of anorexia of ageing potentially co-exist, but either alone are sufficient to cause low macro- and micro-nutrient intake, and loss of lean and fat body mass, with correspondingly adverse effects on health. Currently appetite loss is assessed clinically through questionnaires such as the Malnutrition Universal Screening Tool (MUST) or the Simplified Nutritional Appetite Questionnaire (SNAQ). Both are short questionnaires and do not categorise the type of anorexia. A MUST score is calculated from three factors: body mass index (BMI), unplanned weight loss and Acute disease. A SNAQ score is calculated from four questions each scored on 5-point scales; two related to appetite (appetite and fullness when eating), one related to pleasure (food tastes bad/good) and one related to eating frequency (number of meals per day). As a group of researchers we have designed and will now test questionnaires that are able to define the type of anorexia of ageing from a behavioural questionnaire.