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This content, which is intended for UK healthcare professionals only, has been developed and funded by Boehringer Ingelheim. Dr Steve Holmes, GP, received payment for involvement in the development and accuracy review of this content. Mr Ron Flewett also received payment for involvement in the development of this content as a trustee and spokesperson of the Pulmonary Fibrosis Trust.
Idiopathic pulmonary fibrosis (IPF), the most common form of lung fibrosis, is a progressive, irreversible and life-limiting condition.1,2,3 IPF is one of more than 200 lung diseases known as interstitial lung diseases (ILDs), relating to the interstitium – the tissue between the air sacs of the lungs.4 Patients with IPF present with increasing breathlessness and fatigue and many also develop a persistent, dry cough, which can prove difficult to treat.3,5
IPF occurs when tissue in the lungs becomes inflamed and scarred (lung fibrosis). Fibrosis, or scarring, can be part of the healing response to injury, but fibrosis as a disease process occurs when restoration to normal tissue does not occur.6 The scar tissue, which forms on the alveoli, causes the lungs to become stiff and less elastic, which impairs gas exchange.3,7,8 This impairment of gas exchange leads to a decline in lung function and, ultimately, death from respiratory failure.3
Over time, the lungs develop a ‘honeycomb appearance’. Although its identification is often subjective, honeycombing is a common feature of IPF seen on high-resolution computed tomography (HRCT) and is crucial for an accurate diagnosis.9
The honeycomb changes (arrowheads) and traction bronchiectasis (arrow) indicate the presence of advanced fibrosis.
HRCT scan of the lungs of an IPF patient.10 Republished with permission of McGraw-Hill Companies, from Fishman’s Pulmonary Diseases and Disorders, Meltzer EB and Noble PW, 4th edition 2007; permission conveyed through Copyright Clearance Center, Inc.
‘Idiopathic’ means the cause of the scarring to the lungs in IPF is unknown.11 However, potential links with some environmental factors have been identified.12 Genetics could also play a role in IPF.13
While cigarette smoking is one of the most recognised risk factors for development of IPF, other risk factors may include exposure to metal dust, wood dust, asbestos, silica or coal.12,14 Occupations related to farming and livestock have also been associated with an increased risk of developing IPF.12
Some research suggests that the scarring to the lungs may be related to acid reflux from the stomach.15 There is also some evidence that connects viral and bacterial infections with IPF and other fibrotic lung diseases.16
ILDs can also be caused by chemotherapeutic agents, antibiotics, antiarrhythmic drugs, and immunosuppressive agents.17
Although it should be recognised that where the exposure to occupational triggers, or specific medications, is linked with ILD, the cause is known and therefore the condition is no longer ‘idiopathic’.
While IPF is still relatively rare, there is evidence to suggest it is more common than previously thought.18 According to the European Medicines Agency definition, a rare disease affects ≤5 in 10,000 people.19
The National Institute for Health and Care Excellence (NICE) estimates that 15-25 people per 100,000 in the UK have IPF.20 However, evidence exists to suggest it may be closer to more than double this estimate. According to an analysis of the British Thoracic Society’s 2006 ‘Burden of Lung Disease’ report, an estimated 32,500 people in the UK live with IPF, a prevalence rate of about 50 people every 100,000. There are around 6,000 new cases diagnosed each year.18
Most commonly, people diagnosed with IPF are over the age of 40.21 The chances of diagnosis increase significantly as people get older, with around 85% of diagnoses being made in people aged over 70. IPF is 50% more common in men than women.18
Unlike other lung diseases, rates of IPF in the UK do not appear to be affected by socio-economic status. However, there are regional differences in prevalence. According to data collected by the British Lung Foundation, prevalence is generally highest in Northern Ireland, north-west England, Scotland and Wales, and IPF is least common in London. The reasons for this are unknown.22
5,300 people every year die from IPF.18 The median survival rate of patients with IPF is 3 years following diagnosis, with 34% of patients surviving 5 years.23 This 5-year survival rate is worse than some common cancers, including bowel or colorectal (58-59%), breast (85%) and prostate cancer (87%).23,24,25
Seasonal variability has been observed in IPF death rates, although the precise aetiology associated with this is not well understood. Findings from research using death records in the USA found that the mortality rate among patients with IPF or pulmonary fibrosis (PF) was 17.1% higher in winter (p < 0.0001), 12.7% higher in spring (p < 0.0001), and 5.2% higher in autumn (p = 0.0002) than in summer months.26