Orexigenic Agents in Geriatric Clinical Practice

Vishal Viswambharan; Jothika N Manepalli; George T Grossberg


Aging Health. 2013;9(1):49-65. 

In This Article

Scope of the Problem

Involuntary weight loss (IWL) is clinically defined as a loss of 5% or more of an individual's baseline bodyweight in 1 month or a loss of 10% in a 6-month period.[1] IWL of 4–5% or more of bodyweight within 1 year, or 10% or more over 5–10 years or longer, is associated with increased mortality or morbidity or both; the rate of increased mortality ranges from 9% to as high as 38%.

The loss of bodyweight and fat late in life is associated with premature death and increased risk of disability, even after excluding elderly subjects who have a pre-existing disease.[2] When examining the population admitted to either a geriatric acute care ward or a rehabilitation ward, 33% of female patients and 27% of male patients were anorexic.[3] Until recently, clinicians simply addressed the broad concept of IWL as a loss of muscle mass, sometimes combined with loss of fat; however, it is now feasible to distinguish between three categories of IWL: starvation; sarcopenia; and cachexia, each with its own root cause and prognosis.[4]

Starvation is a pure deficiency in the amount of calories consumed compared with the amount of calories utilized, resulting in a loss of both fat and muscle mass. This condition can be remedied through the sole intervention of replenishing nutrients.

Sarcopenia is generally characterized as an age-related loss of muscle mass, but is also seen concurrently with prolonged bed rest and physical inactivity.[5,6] Current research indicates that sarcopenia is associated with muscle atrophy, a decrease in proliferation of satellite cells and accumulation of intramuscular fat.[7] This condition, most commonly seen in the elderly, can result in not only poor quality of life (QoL), but, if left untreated, can lead to patient death.[7,8]

Cachexia is a condition of physical wasting with loss of weight and muscle mass due to underlying illness or chronic disease. Owing to the comorbidities associated with cachexia, it is imperative for clinicians to distinguish between this condition and starvation, sarcopenia, and other possible causes of weight loss such as malabsorption, depression and hyperthyroidism.[9,10]

Frailty encompasses the concepts of lethargy, sluggishness, weakness, decreased physical activity and exhaustion related to muscle loss.[11] Fried, in conjunction with other researchers, developed five criteria pertaining to a study of cardiovascular health (weight loss, hand grip strength, self-reported exhaustion, gait speed and calories expended per week) and developed a frailty phenotype that predicted future hospitalization and patient mortality.[11] Patients who were over the age of 65 years were considered frail if three or more of the above criteria were positive; whereas patients with only one or two positive criteria were 'prefrail', and patients who did not meet any of the criteria were deemed not frail.

IWL is most commonly observed among elderly patients, affecting 13% of patients who live independently and 50–60% of nursing home residents.[12,201] Overall, the prevalence of IWL among the elderly is 15–20%, and there is little difference in prevalence between men and women. This rate of occurrence can increase to as high as 27% in high-risk populations such as the independent-living frail elderly receiving community services.

It is well known that in hospitals, the mortality rate in elderly patients, particularly those with low baseline bodyweight, is high. If the fluctuation from baseline weight is greater than 5% in a period of 6 months, it needs to be investigated further.[1,13] Between 2008 and 2050, the US population aged 65 years and older will more than double, and the number of people aged 85 years and older is expected to more than triple during this same time period (US Census Bureau, 2010).[202] The first of the baby boomers turned 65 years in the year 2011, and all individuals born between 1946 and 1964 will be aged 65 years and older by the year 2030, by 2030 this will account for 20% of the overall US population.[203]

The percentage of people aged over 65 years has been increasing steadily in the last several decades. According to recently available data published in 2010, there are 1.6 million people aged 65 years and older in the long-term care facilities in the USA.[204] IWL, which is considered a sentinel event in this subgroup of population, is also a major predictor for the decline in activities of daily living and increased rates of hospitalization.[14,15]