The incidence of organising pneumonia (OP) is somewhat uncertain and estimates are commonly drawn from registries which may result in an overestimate of disease incidence but is between 0.5 to 1.5 per 100,000.[31]Gudmundsson G, Sveinsson O, Isaksson HJ, et al. Epidemiology of organising pneumonia in Iceland. Thorax. 2006 Sep;61(9):805-8.
https://thorax.bmj.com/content/61/9/805.long
http://www.ncbi.nlm.nih.gov/pubmed/16809413?tool=bestpractice.com
[32]Raghu G, Meyer KC. Cryptogenic organising pneumonia: current understanding of an enigmatic lung disease. Eur Respir Rev. 2021 Sep 30;30(161).
http://www.ncbi.nlm.nih.gov/pubmed/34407978?tool=bestpractice.com
The incidence of OP is estimated at 1.97 per 100,000 in Iceland and in the rest of the world ranges from 0.2 to 1.45 per 100,000 or is thought to be approximately 5% of interstitial lung disease patients noted in these registries.[31]Gudmundsson G, Sveinsson O, Isaksson HJ, et al. Epidemiology of organising pneumonia in Iceland. Thorax. 2006 Sep;61(9):805-8.
https://thorax.bmj.com/content/61/9/805.long
http://www.ncbi.nlm.nih.gov/pubmed/16809413?tool=bestpractice.com
The fact that the data is sourced from registries may result in some inaccuracy. The incidence does not differ significantly worldwide.[33]Epler GR. Bronchiolitis obliterans organizing pneumonia: definition and clinical features. Chest. 1992;102(1 suppl):2S-6S.
https://www.sciencedirect.com/science/article/pii/S0012369216348759?via%3Dihub
http://www.ncbi.nlm.nih.gov/pubmed/1623805?tool=bestpractice.com
OP occurs equally among men and women, and is not related to smoking. In the Iceland dataset, cryptogenic OP had an incidence of 1.1 per 100,000 while secondary OP had an incidence of 0.87 per 100,000.[31]Gudmundsson G, Sveinsson O, Isaksson HJ, et al. Epidemiology of organising pneumonia in Iceland. Thorax. 2006 Sep;61(9):805-8.
https://thorax.bmj.com/content/61/9/805.long
http://www.ncbi.nlm.nih.gov/pubmed/16809413?tool=bestpractice.com
A similar trend is reflected in an Italian study.[34]Cazzato S, Zompatori M, Baruzzi G, et al. Bronchiolitis obliterans-organizing pneumonia: an Italian experience. Respir Med. 2000 Jul;94(7):702-8.
https://www.sciencedirect.com/science/article/pii/S0954611100908059?via%3Dihub
http://www.ncbi.nlm.nih.gov/pubmed/10926343?tool=bestpractice.com
In other studies, however, the incidence of secondary OP was as high as 87% of the total number of patients presenting with OP.[35]Zhang Y, Li N, Li Q, et al. Analysis of the clinical characteristics of 176 patients with pathologically confirmed cryptogenic organizing pneumonia. Ann Transl Med. 2020 Jun;8(12):763.
https://atm.amegroups.com/article/view/45799/html
http://www.ncbi.nlm.nih.gov/pubmed/32647688?tool=bestpractice.com
It is noteworthy that in a Chinese study, all patients had follow up by phone calls for 4 years after inclusion in study, and 4% of those originally classified as cryptogenic OP had reclassification as secondary OP.[36]Zhou Y, Wang L, Huang M, et al. A long-term retrospective study of patients with biopsy-proven cryptogenic organizing pneumonia. Chron Respir Dis. 2019 Jan-Dec;16:1479973119853829.
https://journals.sagepub.com/doi/10.1177/1479973119853829
http://www.ncbi.nlm.nih.gov/pubmed/31159568?tool=bestpractice.com