What are the top 10 health conditions based on International Classification of Diseases, 9th Revision (ICD-9) diagnoses?

Top 10 Health Conditions Based on ICD-9 Diagnoses

The most prevalent health conditions based on ICD-9 diagnostic codes in the United States are hypertension, hyperlipidemia, ischemic heart disease, diabetes mellitus, arthritis, heart failure, anemia, chronic kidney disease, chronic obstructive pulmonary disease (COPD), and atrial fibrillation, with hypertension affecting over 80% of elderly Medicare beneficiaries with cardiovascular disease. 1

Most Common Conditions in the General Population

Based on 2012 Medicare data for beneficiaries ≥65 years of age, the following conditions represent the most prevalent diagnoses:

Primary Conditions (Ranked by Prevalence)

• Hypertension - The single most common condition, affecting 81.3-89.0% of patients with cardiovascular disease depending on the specific cardiac condition present 1

• Hyperlipidemia (High Cholesterol) - The second most prevalent condition, affecting 62.6-69.9% of patients with cardiovascular disease 1

• Ischemic Heart Disease - Affects a substantial portion of the elderly population and ranks among the top three conditions across multiple disease categories 1

• Diabetes Mellitus - Present in 37.1-47.1% of patients with cardiovascular conditions, representing a major chronic disease burden 1

• Arthritis - Affects 40.6-45.6% of patients with cardiovascular disease, making it one of the most common musculoskeletal conditions 1

• Heart Failure - Present in 36.3-50.9% of patients with other cardiovascular conditions, representing a significant cause of morbidity and mortality 1

• Anemia - Affects 38.7-51.2% of patients with cardiovascular disease, with higher prevalence in those with heart failure 1

• Chronic Kidney Disease - Present in 30.2-44.8% of patients with cardiovascular conditions, with ICD-9 codes 585.1-585.6 used for staging 1

• Chronic Obstructive Pulmonary Disease (COPD) - Affects 21.0-30.9% of patients with cardiovascular disease 1

• Atrial Fibrillation - Present in 18.7-28.8% of patients with other cardiovascular conditions 1

Most Common Comorbidity Combinations

When examining patients with multiple chronic conditions, specific dyads and triads emerge as most prevalent:

Top Dyads (Two Conditions)

• High cholesterol and high blood pressure - Affects 57.2% of Medicare beneficiaries with ≥2 comorbidities 1
• High blood pressure and ischemic heart disease - Present in 36.8% of patients with multiple conditions 1
• High blood pressure and arthritis - Affects 33.3% of patients with multiple comorbidities 1

Top Triads (Three Conditions)

• High cholesterol, high blood pressure, and ischemic heart disease - The most common triad, affecting 35.8% of patients with ≥3 comorbidities 1
• High cholesterol, high blood pressure, and diabetes mellitus - Present in 31.7% of patients with multiple conditions 1

Leading Causes of Death (ICD-9 Classification)

The top 10 causes of death in the United States based on ICD classification are:

1. Diseases of heart - The leading cause of death 2
2. Malignant neoplasms (Cancer) - Second leading cause 2
3. Cerebrovascular diseases (Stroke) - Third leading cause 2
4. Chronic lower respiratory diseases - Fourth leading cause 2
5. Accidents (unintentional injuries) - Fifth leading cause 2
6. Diabetes mellitus - Sixth leading cause 2
7. Influenza and pneumonia - Seventh leading cause 2
8. Alzheimer's disease - Eighth leading cause 2
9. Nephritis, nephrotic syndrome and nephrosis - Ninth leading cause 2
10. Septicemia - Tenth leading cause 2

These 10 conditions account for nearly 80% of all deaths in the United States 2

Important Coding Considerations

• ICD-9 to ICD-10 transition challenges - Significant discontinuities occurred for certain conditions during the coding system transition, with complications like pneumonia showing 34% decrease in coding (OR=0.66), while sepsis showed 154% increase (OR=2.54) 3

• Accuracy varies by condition - ICD-9-CM codes demonstrate high specificity (>0.95) but low sensitivity (≤0.76) for cardiovascular risk factors, meaning conditions can be "ruled in" but not necessarily "ruled out" 4

• Chronic conditions most reliable - Common chronic conditions like coronary artery disease, stroke, heart failure, diabetes, and hypertension have positive predictive values >0.95 when using ICD-9 codes 4

• Discordance in coding algorithms - Up to 32.9% discordance exists between different ICD code lists used in literature versus standardized algorithms, with ICD-10 showing higher discordance (35.7%) than ICD-9 (22.2%) 5