What is the prevalence of Interstitial Lung Disease (ILD) in a specific location?

Prevalence of Interstitial Lung Disease

The overall prevalence of ILD in the general population ranges from 67.2 to 80.9 per 100,000 persons, with males having consistently higher rates than females. 1

General Population Estimates

The most comprehensive population-based data comes from a registry study in New Mexico that established baseline prevalence figures:

• Males: 80.9 per 100,000 1
• Females: 67.2 per 100,000 1
• Overall incidence: 31.5 per 100,000/year in males and 26.1 per 100,000/year in females 1

More recent estimates suggest the prevalence may range from 72.1 to 164.2 cases per 100,000 Europeans, indicating potential geographic variation and increasing recognition over time. 2

United States-Specific Data

In the United States, ILD affects approximately 650,000 people and causes approximately 25,000 to 30,000 deaths per year. 3 This represents a substantial disease burden that has increased significantly over recent decades.

Distribution by ILD Subtype

The prevalence varies considerably by specific ILD diagnosis:

• Idiopathic pulmonary fibrosis (IPF): Accounts for approximately one-third of all ILD cases, with incidence of 14.6 per 100,000 person-years and prevalence of 58.7 per 100,000 persons 3, 4
• Connective tissue disease-associated ILD: Represents approximately 25% of all ILD cases and accounts for 20% of the CTD-ILD subset 3, 2
• Hypersensitivity pneumonitis: Accounts for 15% of ILD cases 3
• Pulmonary fibrosis and IPF combined: Account for more than 45% of all ILD diagnoses 2

High-Risk Populations

Smokers Undergoing Lung Cancer Screening

Among current and former smokers undergoing chest CT screening, the prevalence of interstitial lung abnormalities (ILAs) or ILD is 8% (95% CI, 7-10%). 2 This translates to 80 individuals with ILAs/ILD identified per 1,000 smokers screened. 2

Connective Tissue Disease Patients

• Systemic sclerosis: Approximately 50% develop ILD, with 35% of limited cutaneous SSc and 56% of diffuse cutaneous SSc having ILD at baseline 2
• Rheumatoid arthritis: Prevalence estimates range widely from 4% to 68% depending on detection methods, with 33% showing HRCT abnormalities but only 14% considered clinically significant 2

Occupational Exposures

• Farmer's lung: Prevalence ranges from 11.5 to 192 per 100,000 population in England 2
• Pigeon breeders: Clinical disease may affect up to 20% of those with high antigen exposure 2

Geographic and Socioeconomic Variations

Prevalence estimates are substantially lower in developing countries (0.4-1.2 cases per 100,000 per year in South America) compared to developed nations, likely reflecting limited access to high-resolution CT, spirometry, and multidisciplinary diagnostic teams rather than true lower disease burden. 4 The actual burden in highly populated regions like Brazil, Russia, India, and China may include approximately 2 million people living with IPF alone. 4

Temporal Trends

The Global Burden of Disease Study reported that ILD ranked 40th in global years of life lost in 2013, representing an 86% increase compared to 1990. 4 Multiple studies demonstrate increasing incidence and prevalence of ILD over time, though this may reflect improved recognition and diagnostic capabilities rather than solely true increases in disease occurrence. 5

Undiagnosed Disease

An estimated 1.8% of all deaths have preclinical or undiagnosed ILD identified at autopsy, suggesting substantial underdiagnosis in the general population. 1 This underscores that the true prevalence of ILD may be considerably higher than clinical registry data suggest. 1

Critical Considerations

The prevalence data should be interpreted cautiously because:

• Case ascertainment methods vary widely across studies, affecting comparability 5
• Access to diagnostic imaging and specialist care creates major disparities, particularly in low- and middle-income countries 4, 5
• Occupational and environmental ILDs are likely substantially underreported, especially in developing nations where millions of workers face relevant exposures 6
• Socioeconomic inequalities affect both morbidity and mortality within and across countries 5