Loss of appetite (anorexia) is a recognised, eminent factor leading to weight loss in old age and has been estimated to afflict up to 25 per cent of elderly in the community, 62 per cent in hospitalised and a whopping 85 per cent in nursing homes.

Subsequent undernutrition results in decreased capacity to combat infections, recover from physical stress and insult, compensate for the effects of medical conditions, build or maintain muscle mass and contributes towards frailty in general, which sets off a vicious cycle fuelling further anorexia.

Hunger signals from the stomach to the brain via the hunger hormone (ghrelin) may also diminish with age, whereby the body is led into a state where despite a calorie deficit and weight loss, the appropriate stimuli driving compulsion to eat become progressively attenuated. This is evident in dementia, for instance, whereby attempts at offering food may be met with hostile rejection.

Anorexia is a multifactorial phenomenon influenced by changes throughout the ageing alimentary tract. These start at the mouth, with a reduction in the smell and taste sensations that would normally testify to palatability, or otherwise, of presented food stuffs. For instance, Parkinson’s disease is associated with a reduced sense of smell.

There is also reduced saliva production or ‘dry mouth’, needed to adequately moisten solid food bites, aid maceration with formation of soft, malleable, lubricated boluses (chewed food) in preparation for swallowing and where initial chemical digestion of starches and complex sugars takes place. Additionally, poor dentition and poorly fitting, or painful, dentures mean effective chewing is impaired, which further compromises bolus processing.

Ability of the gullet or food pipe to propel a food bolus from the mouth to the stomach by rhythmic, coordinated contractions, may become impaired with dementia, Parkinson’s disease, strokes and cumulative damage due to years of acid overflowing back up the gullet from the stomach. Such malfunction may result in choking as small proportions of food or drink may be inadvertently diverted into the lungs. This often-subtle occurrence is easily dismissed and complications such as chest infections ensue.

The stomach becomes less compliant (stretchable) to accommodate volume expansion with age, while protein digesting enzymes released by the dedicated stomach lining also gets curtailed; moreover, some elderly may develop a degenerative condition of the lining itself (atrophic gastritis) which leads to less acid being produced, all of which hinders proper food digestion at this stage. There is also reduced ability of the stomach to contract and shift food to the next portion of the alimentary tract, the small bowel. Parkinson’s disease, diabetes and other conditions affecting the nerves that supply the stomach also contribute to reduced stretchability and sluggish contractions.

Age registers a decline in release of enzymes by the pancreas in particular; this is a key function which permits further breakdown of complex nutrients into elemental products that are easily absorbed. However, effective absorption also depends on the provision of a large surface area in the form of densely convoluted finger-like projections of the small bowel lining, which may deteriorate and flatten with age.

Interventions to improve appetite in elderly remain challenging

Overgrowth of the bacterial population residing within the intestines also typifies the ageing gut. This gut flora proliferation, manifesting as bloating, stomach upset and diarrhoea, leads to impaired absorption of nutrients, vitamins and minerals, which are harnessed by the resident bacteria or lost to the diarrhoea instead.

Constipation effects up to 50 per cent of nursing home residents. The entire bowel movements tend to become sluggish with age, on account of both degeneration of the nerves within the wall that would stimulate the muscular layer encasing the bowels to contract, but also through reduced physical activity in general, which normally would have a beneficial effect in aiding propulsion of waste matter in the form of faeces.

When faeces dwells for prolonged periods in the large bowel, it tends to lose water content, consolidating to form a hardened plug. As liquid stool further up may be forced past this plug under pressure, watery bouts does not necessarily preclude such severe constipation. Moreover, the high pressures generated within the large bowel in attempting to expel faeces over years, together with gaseous distension, stretches the bowel wall, compromising its ability to contract further as it loses elasticity and recoil potential, also leading to formation of redundant outpouchings or ‘diverticuli’.

Medication side effects play an important role in all the above.  Painkillers, antibiotics and acid suppressing agents, among others, may form an unpleasant taste which puts one off food. Many tranquillisers, antidepressants, drugs used against bladder and muscle spasms, inhibit saliva secretion contributing towards a dry mouth. Medications that suppress stomach acid may hinder digestion and the reduced acidity itself may foster overgrowth of bacteria in the small bowel further down.

Conversely, many painkillers, anti-inflammatory agents, lipid-lowering agents and steroids can cause damage and inflammation of the stomach and small bowel lining (‘heartburn’) potentially leading to ulcers forming.

Constipation may result from iron and calcium supplements, antiparkinsonian drugs (this apart from the condition itself), morphine-related painkillers (such as codeine), blood pressure drugs known as calcium channel blockers, and lastly through the same drugs that cause a dry mouth.

Constipation and dry mouth are two drug side effects sharing a common mechanism of action − the inhibition of acetylcholine, a chemical neurotransmitter required to both produce saliva while also stimulating the muscles within the stomach and bowels to contract and propel processed food along the alimentary tract.

Interventions to improve appetite in the elderly remain challenging, particularly with dementia or psychiatric cases where ability to adhere to management strategies may be limited. Beyond education, exercise and optimisation of regular medications, meal adjustments is advocated, including flavour enhancement, wider variety and smaller, frequent servings.

Artificial saliva spray, lozenges or gum helps to moisten the mouth. Nutritional supplementation in the form of calorie-rich and protein-rich drinks, shakes or powders, and vitamin/mineral formulations may be employed as adjuncts or alternatives to traditional diet, and may be tailored to individual needs and requests under the guidance of nutritionists.

Few pharmacological appetite stimulant options are available in Malta, namely;

• Cyproheptadine (as tablets or a branded syrup): a drug that owes its appetite-enhancing action due to inhibition of histamine (a chemical involved in allergies and inflammation) in the brain. Other antihistamines and some antidepressants such as mirtazapine and mianserin also share this mechanism of action.

• Glucocorticoids (steroids); the ‘stress hormone’ seems to promote uncontrolled eating, especially of highly palatable, high-calorific foods via enhancing the brain-reward mechanism, or hedonistic drive towards increased food indulgence.

• Megestrol acetate and the progestogen-only contraceptive pill (POCP) act akin to steroids but additionally stimulate Neuropeptide Y, a chemical produced by the brain that directly increases drive to consume high-calorific foods and reduces satiety sensation.

Naturally, the side effects of these drugs must be considered, but as a last resort, in the recalcitrant elderly who is wasting away, it would seem a disservice not to try them.

Neville Aquilina is a consultant geriatrician and physician. Aquilina is also a council member of the Maltese Association of Gerontology and Geriatrics (MAGG).