What are the causes of lethargy in an elderly patient?

From the Guidelines

Lethargy in elderly patients is most commonly caused by a combination of factors including medication side effects, dehydration, malnutrition, infections, and metabolic disturbances, and a comprehensive approach is needed to evaluate and treat the underlying cause. When evaluating lethargy in an elderly patient, it is essential to consider the potential causes, including medication side effects, dehydration, malnutrition, infections, depression, sleep disorders, anemia, thyroid dysfunction, heart disease, and neurological conditions like dementia 1. Common medications that cause lethargy include sedatives, antidepressants, antipsychotics, and certain blood pressure medications, and polypharmacy, or taking multiple medications, increases this risk significantly 1. Underlying medical conditions such as urinary tract infections, pneumonia, or heart failure can manifest primarily as lethargy in older adults rather than typical symptoms, and metabolic disturbances including electrolyte imbalances, vitamin B12 deficiency, and diabetes can contribute to fatigue 1. Psychological factors like depression, grief, and social isolation are also important contributors to lethargy in elderly patients 1. A comprehensive approach is needed to evaluate lethargy in elderly patients, including medication review, physical examination, basic laboratory tests (complete blood count, metabolic panel, thyroid function), and assessment of mental health 1. Treatment should target the underlying cause, whether adjusting medications, treating infections, correcting nutritional deficiencies, or addressing psychological needs, and maintaining adequate hydration, proper nutrition, regular physical activity, and good sleep hygiene can help prevent lethargy in elderly individuals 1. It is also important to note that hypoglycemia is a common cause of lethargy in elderly patients, particularly those with diabetes, and can be associated with poor outcomes, including increased mortality 1. Therefore, a comprehensive geriatric assessment (CGA) is recommended to evaluate elderly patients with lethargy, as it can help identify underlying causes and guide treatment 1.

From the FDA Drug Label

In mild cases, symptoms include drowsiness, mental confusion, paradoxical reactions, dysarthria and lethargy. The incidence of sedation and unsteadiness increased with age

• Lethargy in an elderly patient may be caused by:
  • Benzodiazepine overdose or high doses, as seen with lorazepam 2
  • Adverse reactions to benzodiazepines, such as sedation, which increases with age 2
• It is essential to consider multiple factors, including the patient's medication regimen and potential interactions, when assessing the cause of lethargy in an elderly patient.

From the Research

Causes of Lethargy in Elderly Patients

• Lethargy in elderly patients can be caused by various factors, including infections such as pneumonia 3
• Pneumonia in the elderly often presents with atypical features, including confusion, lethargy, and general deterioration of condition 3
• Hypoglycemia can also be a cause of lethargy, particularly in patients with bacteremic pneumococcal infections 4
• Other factors that may contribute to lethargy in elderly patients include fatigue, which is a common complaint in this population 5
• Fatigue in the elderly can be categorized into recent, prolonged, and chronic fatigue, each with different clinical manifestations and predisposing factors 5

Infections and Lethargy

• Community-acquired pneumonia (CAP) is a common medical condition that can cause lethargy in elderly patients 6, 3
• Abnormal glucose levels, including hyperglycemia and hypoglycemia, can be associated with increased length of stay and severity of illness in patients with CAP 6
• Post-admission glucose levels can be associated with healthcare-associated bloodstream infections and pneumonia in hospitalized patients with diabetes 7

Diagnosis and Treatment

• Diagnosis of lethargy in elderly patients requires careful evaluation of the patient's medical history, physical examination, and laboratory tests 3, 4
• Treatment of lethargy in elderly patients depends on the underlying cause, and may include antibiotic therapy for infections, glucose control for hyperglycemia or hypoglycemia, and non-pharmacologic interventions such as exercise and behavior modification for fatigue 3, 5