Idiopathic Pulmonary Fibrosis (IPF)


Idiopathic pulmonary fibrosis (IPF) is a rare, progressive, fatal lung disease. It is a form of interstitial lung disease (ILD) and makes up 17% to 86% of ILD cases.1 Common symptoms of the disease include exertional dyspnea, chronic cough, bibasilar inspirational crackles on lung auscultation, and finger clubbing.2

The prognosis and clinical course of the disease can be quite variable, with some patients experiencing rapid decline while others experience a slower progression. As many as 10% to 20% of patients experience acute exacerbations of the disease that can affect the progression and often be fatal.3 

Several studies have attempted to estimate the incidence and prevalence of IPF over the years. 

IPF Incidence

Estimates of IPF incidence have varied between studies and countries. Most of the estimates come from North America and Europe, with a few from Asia and one from Brazil.1 Large database studies in Europe provided incidence rates ranging from 2.91 to 8.65 cases per 100,000 people per year, however, the more recent studies showed higher rates.1 A recent study in Italy used multiple methods of estimation and Health Search Database information from 2002 to 2017 to get incidence rates that varied from 0.10 to 3.77 per 100,000 person-years.4

In North America, estimates have ranged from 6.8 to 93.7 per 100,000 per year, with large variability depending on the population used in the study.1 A study in the US that analyzed insurance claims through Medicare in patients 65 and over between 2001 and 2011 found an incidence during this time period of 93.7 cases per 100,000 person-years.5 The same group later analyzed commercial insurance claims in the US for people aged 18 to 64 between the years of 2004 and 2010 in a separate study.6 The results of this study found an incidence of 7.9 per 100,000 people in 2005, which slightly decreased to 5.8 cases per 100,000 in 2010.6 The decrease was attributed to lower incidence rates in patients aged 18 to 44 while older patient rates remained fairly constant.5 Some concerns over the methodology used in this study have been expressed, however, which may affect how generalizable the results are over the whole US population.7

Large database studies in Asia resulted in much lower incidence rates than those in Europe and North America, with rates between 2 and 4.16 per 100,000 people per year.1 A recent study of Taiwanese patients utilized information from the Taiwan National Health Insurance Research Database between 2001 and 2011.2 The study found that the incidence rate was fairly stable and ranged from 0.7 to 1.3 cases per 100,000 people per year, much less than rates found in Europe and North America.2

The only large database study for South America was published in 2013 and used Ministry of Health data from Brazil during the period of 1996 to 2010. A low incidence of 0.48 per 100,000 people per year was reported during this study period.1

A review article published in 2015 attempted to analyze and combine incidence estimates from multiple studies and geographic regions to give better overall estimates of incidence.8 Because of the variability in study design and different time periods, the authors were not able to perform a meta-analysis of overall rates using all of the data. The study then excluded studies from Asia and South America, those containing data before 2000 when the earliest consensus diagnosis guidelines were published, and those utilizing questionnaire surveys as they were deemed less reliable. Finally, the authors used narrow criteria to get an estimate for Europe and North America. The overall results yielded an incidence of 2.8 to 9.3 cases per 100,000 people per year. The article also reported that most studies tended to show an increase in incidence over time, especially in the UK, but some studies showed plateauing or a decrease in the US.8

It is thought that the increased incidence seen in many studies may be due to rising awareness of IPF among physicians as well as better diagnostic criteria and technology.4

IPF Prevalence

Estimates of prevalence also vary between studies and geographic regions. Some earlier estimates of the prevalence of IPF varied from 2 to 29 cases per 100,000 people per year.9 The previously mentioned US Medicare study showed that prevalence rates increased from 202.2 cases in 2001 to 494.5 cases per 100,000 per year in 2011.5 Prevalence rates ranging from 0.8 to 24.3 per 100,000 were estimated for Italian patients using Health Search Database information in the study also mentioned above.4 The prevalence appeared to be steadily increasing during the time period in this study as well.4 The Taiwanese study also found increasing rates of prevalence, which started at 3.1 per 100,000 per year in 2006 and grew to 6.4 per 100,000 by 2011.2

The increase in prevalence is most likely due to increasing diagnostic rates and prolonged survival among patients due to earlier diagnosis and better treatment and management of the disease.4

References

  1. Wakwaya Y, Brown KK. Idiopathic pulmonary fibrosis: epidemiology, diagnosis andoutcomes. Am J Med Sci. 2019;357(5):359-369. doi:10.1016/j.amjms.2019.02.013
  2. Yang SN, Perng DW, Ko HK, et al. Epidemiologic analysis of Taiwanese patients with idiopathic pulmonary fibrosis. Healthcare (Basel). 2020;8(4):580. doi:10.3390/healthcare8040580
  3. Sauleda J, Núñez B, Sala E, Soriano JB. Idiopathic pulmonary fibrosis: epidemiology, natural history, phenotypes. Med Sci (Basel). 2018;6(4):110. doi:10.3390/medsci6040110
  4. Harari S, Davì M, Biffi A, et al. Epidemiology of idiopathic pulmonary fibrosis: a population-based study in primary care. Intern Emerg Med. 2020;15(3):437-445. doi:10.1007/s11739-019-02195-0
  5. Raghu G, Chen SY, Yeh WS, et al. Idiopathic pulmonary fibrosis in US Medicare beneficiaries aged 65 years and older: incidence, prevalence, and survival, 2001-11. Lancet Respir Med. 2014;2(7):566-572. doi:10.1016/S2213-2600(14)70101-8
  6. Raghu G, Chen SY, Hou Q, Yeh WS, Collard HR. Incidence and prevalence of idiopathic pulmonary fibrosis in US adults 18-64 years old. Eur Respir J. 2016;48(1):179-186. doi:10.1183/13993003.01653-2015
  7. Harari S, Caminati A, Madotto F, Conti S, Cesana G. Epidemiology, survival, incidence and prevalence of idiopathic pulmonary fibrosis in the USA and Canada. Eur Respir J. 2017;49(1):1601504. doi:10.1183/13993003.01504-2016
  8. Hutchinson J, Fogarty A, Hubbard R, McKeever T. Global incidence and mortality of idiopathic pulmonary fibrosis: a systematic review. Eur Respir J. 2015;46(3):795-806. doi:10.1183/09031936.00185114
  9. Raghu G, Collard HR, Egan JJ, et al.; ATS/ERS/JRS/ALAT Committee on Idiopathic Pulmonary Fibrosis. An official ATS/ERS/JRS/ALAT statement: idiopathic pulmonary fibrosis: evidence-based guidelines for diagnosis and management. Am J Respir Crit Care Med. 2011;183(6):788-824. doi:10.1164/rccm.2009-040GL

Reviewed by Harshi Dhingra, MD, on 7/1/2021.

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