Community-Acquired Pneumonia in the Elderly — Etiology, Clinical Features and Management

Community-Acquired Pneumonia in the Elderly — Etiology, Clinical Features and Management 15 marks High-Yield Points Definition and Epidemiology

Definition: acute infection of the lung parenchyma acquired outside hospital, with new radiographic consolidation. Unlike bronchitis (which involves only the airways and has a benign course), pneumonia involves the alveoli.

Burden: pneumonia and influenza together are the sixth leading cause of death in those over 65 and the leading infectious cause of death in the elderly. Incidence rises from 18 per 1000 at age 65–69 to 52 per 1000 over age 85. Over 40% of elders with CAP require hospitalisation; mortality is about 10%, rising to nearly 50% where there is pre-existing cardiopulmonary disease. Two out of three pneumonia hospitalisations are in patients over 70.

Predisposing factors (Pathy's Table 39.1): ageing itself (declining cell-mediated immunity, reduced cough and mucociliary clearance, micro-aspiration), COPD, asthma, sequelae of tuberculosis, diabetes mellitus, heart failure, neurological disease, swallowing disorders, sedative and antipsychotic drugs, gastro-oesophageal reflux, protein-energy malnutrition, and enteral feeding or nasogastric tube. Pneumonia is the commonest specific cause of death in Alzheimer's disease.

Streptococcus pneumoniae is the single most important pathogen — the commonest cause of CAP requiring admission, with a high mortality in the elderly.

Other bacteria: Gram-negative bacilli (after aspiration, hospitalisation or prior antibiotics), Staphylococcus aureus, Haemophilus influenzae, Legionella pneumophila (rarer but severe, high mortality), Mycoplasma pneumoniae, streptococci and Enterobacteriaceae. Anaerobes are common in aspiration pneumonia, and multi-microbial pneumonia is common in the elderly.

Age shifts the spectrum: in older patients S. pneumoniae, H. influenzae and respiratory viruses are commoner, while Legionella, Mycoplasma and Chlamydia are less frequent than in younger adults.

Nursing-home residents: aspiration pneumonia, Gram-negative enteric bacilli and multiple anaerobes predominate. In hospital-acquired pneumonia: S. aureus, Pseudomonas aeruginosa and resistant Gram-negatives.

Viruses cause 10–30% of community-acquired lung infection, often in institutional epidemics — influenza (even in vaccinated patients), RSV, parainfluenza, rhinovirus, adenovirus, and emerging coronaviruses (SARS 2002, MERS 2012, SARS-CoV-2/COVID-19, where case-fatality exceeds 30% in those over 75–80). Always consider M. tuberculosis where illness has evolved over weeks with weight loss.

The classical picture is rarely complete. Fever and cough are absent in 30–40% of cases. Onset is often gradual with less marked signs, causing diagnostic delay.

Respiratory symptoms: cough (productive or dry), purulent sputum, dyspnoea, pleuritic chest pain, haemoptysis. Non-respiratory symptoms: fever, anorexia, chills and sweats.

Geriatric presentations: delirium/acute confusion, falls, functional decline, incontinence, anorexia, tachypnoea alone, or unexplained decompensation of diabetes or heart failure. Tachypnoea is often the earliest and most reliable sign. Hypothermia rather than fever indicates severe disease.

Examination findings to record: respiratory rate >30/min, heart rate >110/min, fever or hypothermia, bronchial breathing, crackles, dullness to percussion, and hypoxaemia on pulse oximetry.

Chest radiograph is the gold standard for documenting parenchymal involvement; the radiographic pattern correlates poorly with the causative organism. A normal film may occur very early in pneumococcal pneumonia. Practical strategy in the community: the British Thoracic Society allows management without a film if pneumonia is likely and admission is not needed; otherwise repeat the film 2–3 days after starting treatment. CT is indicated in difficult cases and can identify very early pneumonia or pulmonary embolism.

Point-of-care lung ultrasound detects B-lines, consolidation ("pulmonary hepatisation"), effusion and pneumothorax, with excellent sensitivity and specificity compared with chest X-ray. It is particularly valuable in nursing homes and home care where imaging is hard to obtain — a technique Pathy's predicts will become a core geriatric skill.

Blood tests: neutrophil leucocytosis (may be absent in older patients with bacterial infection), raised CRP, electrolytes, urea, creatinine and glucose (dehydration, renal failure and hyperglycaemia are common). Arterial blood gas if there is chronic respiratory failure, cyanosis, sweating or reduced consciousness. BNP >300 pg/mL suggests cardiac rather than pulmonary dyspnoea.

Microbiology: blood cultures and sputum examination in all hospitalised patients. Pneumococcal and Legionella urinary antigen only for severe pneumonia needing intensive care, or during an outbreak. Do not send routine urine microscopy/culture — asymptomatic bacteriuria is so common in the elderly that it misleads prescribing. Nasal swab for viral PCR during institutional epidemics.

Decide site of care. Use CURB-65 (Confusion, Urea >7 mmol/L, Respiratory rate ≥30, Blood pressure <90/60, age ≥65) or PSI; but Pathy's stresses that in the frail elderly the decision also depends on severity signs and whether the patient can be cared for at home (Figure 39.1). Note that age ≥65 automatically scores one CURB-65 point, so the score over-triages older patients — combine with clinical and social judgement.

General measures: oral or subcutaneous/intravenous hydration, oral nutritional supplements if malnourished, oral care, pressure-ulcer prevention, early mobilisation, antipyretics if fever >39.5°C or poorly tolerated, non-pharmacological management of delirium, and subcutaneous heparin thromboprophylaxis unless contraindicated.

Supportive respiratory care: nasal oxygen for dyspnoea or hypoxaemia (with caution in hypercapnic chronic respiratory failure); chest physiotherapy; inhaled beta-2 agonists and anticholinergics if bronchial obstruction is present; a short course of systemic corticosteroids for resistant bronchial obstruction; emergency bronchoscopy for large atelectasis from a mucus plug.

Antibiotics (Pathy's Table 39.5, ATS/IDSA 2019) for a comorbid outpatient: a beta-lactam (amoxicillin, amoxicillin-clavulanate, cefpodoxime or cefuroxime) plus a macrolide or doxycycline; or a respiratory fluoroquinolone alone (levofloxacin, moxifloxacin, gemifloxacin — moxifloxacin now restricted for adverse effects). Nursing-home pneumonia requires anaerobic cover: amoxicillin-clavulanate or ceftriaxone or a respiratory fluoroquinolone. Severe or hospital-acquired pneumonia requires broad-spectrum cover, guided by prior antibiotics in the last three months and risk factors for Pseudomonas (bronchiectasis).

The 48-hour review is a critical step. Response is expected within 2–4 days. If afebrile and stable, continue and switch intravenous to oral in the same class. If not improving, consider resistant organisms, virus or tuberculosis, empyema, a non-infectious lung disease, antibiotic adverse effects, or decompensating comorbidity — and re-image, seek urinary antigens, and take infectious disease advice.

Duration and follow-up: total course about 10 days (5 days for azithromycin). Fever, leucocytosis and CRP settle within 2–5 days; cough persists longer. A follow-up chest radiograph is not needed if recovery is clinically complete — radiographic clearance can take up to 12 weeks in the elderly. If lung cancer is suspected, arrange CT and bronchoscopy.

Prevention: annual influenza vaccination for everyone aged 65 and over — it reduces influenza by about 50% and influenza mortality by about 70%; adjuvanted or high-dose vaccine is particularly valuable in institutionalised or chronically ill elders. Add pneumococcal vaccination, COVID-19 and RSV vaccination, smoking cessation, oral and dental hygiene, dysphagia screening and safe feeding practice, avoidance of sedatives and antipsychotics, treatment of reflux, and correction of malnutrition.