What are the top 5 diagnoses accounting for Intensive Care Unit (ICU) admission across different age groups?

Top 5 Diagnoses for ICU Admission by Age Group

Cardiovascular disease is the single most common category of ICU admissions across adult age groups (36.1%), with acute coronary syndrome and heart failure predominating, while the specific diagnostic patterns shift substantially with advancing age, particularly after 65 years when infectious diseases and respiratory failure become increasingly prominent. 1, 2

Young to Middle-Aged Adults (18-64 years)

Top 5 Diagnoses:

1. Acute Coronary Syndrome (31.8% of all cardiac ICU admissions) - This represents the leading cardiac diagnosis requiring intensive care, though proportions vary widely between centers (15-57%) 3

2. Trauma and Traumatic Brain Injury - These conditions account for a substantial proportion of ICU admissions in younger populations, with trauma being a leading indication for critical care 4

3. Sepsis and Septic Shock - Requiring vasopressor support, this represents 21.1% of ICU admissions when considering shock as an indication 3

4. Acute Respiratory Failure - Respiratory insufficiency accounts for 26.7% of ICU admissions, representing the most common single indication for intensive care 3

5. Cardiac Arrest - Accounting for 8.7% of admissions, with the highest mortality rate (38.1%) among all ICU indications 3

Older Adults (65-74 years)

Top 5 Diagnoses:

1. Cardiovascular Disease (36.1% of admissions) - This becomes the dominant category, with acute coronary syndrome and heart failure as primary diagnoses 1, 2

2. Severe Community-Acquired Pneumonia - The incidence rises dramatically with age, from 8.4 per 1,000 in patients 65-69 years, requiring ICU admission when CURB-65 score ≥3 5

3. Chronic Obstructive Pulmonary Disease (COPD) Exacerbations (24.4% prevalence) - This represents a significant proportion of respiratory admissions in this age group 6

4. Sepsis and Septic Shock - Frequency increases with age, particularly in patients with chronic conditions 1

5. Postoperative Monitoring - Approximately 20% of ICU admissions in older adults are for postoperative care after major surgery 1

Elderly Adults (75-84 years)

Top 5 Diagnoses:

1. Heart Failure (increasing to 40.3% prevalence) - This shows marked increase compared to younger elderly patients 6

2. Cardiac Arrhythmias (43.5% prevalence) - Nearly doubles from the 65-74 age group (24.6%) 6

3. Severe Community-Acquired Pneumonia - Incidence continues to rise, with 60-70% of elderly ICU patients developing ARDS 1

4. Cerebrovascular Accidents (Stroke) - This becomes one of the most common specific diagnoses in ICU admissions 4

5. Sepsis with Respiratory Failure - The combination of infectious disease and respiratory insufficiency becomes increasingly common 1, 5

Very Elderly Adults (≥85 years)

Top 5 Diagnoses:

1. Valvular Heart Disease (15.8% prevalence) - More than doubles from the 65-74 age group (7.5%) 6

2. Cardiac Arrhythmias (43.5% prevalence) - Remains the dominant cardiac condition 6

3. Severe Pneumonia - Incidence reaches 48.5 per 1,000 in patients ≥90 years, representing a nearly 6-fold increase from the 65-69 age group 5

4. Acute Respiratory Failure Requiring Mechanical Ventilation - This indication carries particularly high mortality in this age group 1

5. Septic Shock - Requiring vasopressor support, with mortality rates exceeding 30% 3

Critical Age-Related Patterns

The proportion of various comorbidities changes dramatically with advancing age, with cardiovascular conditions peaking in the 7th decade while infectious and respiratory diseases become increasingly prominent after age 75. 6

Declining Conditions with Age:

• Diabetes complications: Decrease from 7.5% to 2.4% across age groups 6
• Alcohol abuse: Drops from 4.1% to 0.6% 6
• COPD: Decreases from 24.4% to 17.4% in the oldest groups 6
• Liver failure: Falls from 5.0% to 1.0% 6

Mortality Considerations by Diagnosis

Cardiac arrest carries the highest mortality rate (38.1%), followed by cardiogenic shock (30.6%) and need for renal replacement therapy (34.5%), regardless of age group. 3

High-Risk Diagnoses:

• Patients requiring mechanical ventilation have 5.87 times higher odds of mortality (95% CI: 3.24-10.65) 2
• Abnormal mental status at admission increases mortality odds by 2.8 times (95% CI: 1.83-4.29) 2
• Overall ICU mortality ranges from 34.1% to 38.7% in resource-limited settings 4, 2

Important Clinical Caveats

Age alone should not determine ICU admission decisions; functional status, frailty using the Clinical Frailty Scale, and severity of acute illness are more important prognostic factors than chronological age. 7, 1

• Advanced age (>75 years) is an independent risk factor for mortality with odds ratios of 1.38-1.53 compared to younger elderly patients 6
• Approximately 50% of ICU survivors >65 years are discharged home, and 83% of patients ≥75 years who survive 4 years after injury live independently 7
• Hospitals account for 17.6% of variability in ICU admission rates independent of patient characteristics, suggesting significant practice variation 8