Objective To estimate the reported incidence of

occupational hypersensitivity pneumonitis (OHP) in the

UK and to consider whether the pattern of attributed

causation has changed over time.

Methods All cases of OHP reported to the SWORD

scheme between January 1996 and December 2015

were classified into 1 of 10 categories of the suspected

agent. Cases were grouped into four 5-year time

periods to examine any changing pattern in incidence

or suspected causation. For each time period, the

annual incidence was calculated using the estimated

number of reported cases and the working population

of the UK.

Results Between 1996 and 2015, there were 202

actual cases of OHP reported to SWORD, equating to

an estimated 818 cases, when adjusting for the

sampling ratio. Over this period, the annual UK

incidence was 1.4 per million workers. The mean (SD)

age of reported cases was 52 (13) years, and cases

were four-times more likely to be men than women.

Over the study period, there was a fall in the proportion

of cases reported to be due to agricultural exposures

(44–12%), and an increase in cases due to

metalworking fluids (MWFs, 2–45%).

Conclusions Over the last 20 years, the incidence of

OHP in the UK has been ∼1–2 cases per million

workers per year. Working with water-based MWFs is

now the most commonly suspected causative exposure

for OHP cases reported to the SWORD scheme in

the UK

Burton

C M Barber

Carder

Demedts

Elder

Fenclová

Fernández Pérez

Hanley

Lacasse

M Carder

McDonald

McNamee

Orriols

Quirce

R Agius

R E Wiggans

Rosenman

Solaymani-Dodaran

Stocks

Objective To estimate the reported incidence of occupational hypersensitivity pneumonitis (OHP) in the UK and to consider whether the pattern of attributed causation has changed over time. Methods All cases of OHP reported to the SWORD scheme between January 1996 and December 2015 were classified into 1 of 10 categories of the suspected agent. Cases were grouped into four 5-year time periods to examine any changing pattern in incidence or suspected causation. For each time period, the annual incidence was calculated using the estimated number of reported cases and the working population of the UK. Results Between 1996 and 2015, there were 202 actual cases of OHP reported to SWORD, equating to an estimated 818 cases, when adjusting for the sampling ratio. Over this period, the annual UK incidence was 1.4 per million workers. The mean (SD) age of reported cases was 52 (13) years, and cases were four-times more likely to be men than women. Over the study period, there was a fall in the proportion of cases reported to be due to agricultural exposures (44-12%), and an increase in cases due to metalworking fluids (MWFs, 2-45%). Conclusions Over the last 20 years, the incidence of OHP in the UK has been ∼1-2 cases per million workers per year. Working with water-based MWFs is now the most commonly suspected causative exposure for OHP cases reported to the SWORD scheme in the UK.</p

Barber, C. M.

Wiggans, R. E.

Carder, M.

Agius, R.

The University of Manchester - Institutional Repository

Epidemiology of occupational hypersensitivity pneumonitis; Reports from the SWORD scheme in the UK from 1996 to 2015

Barber, C.M.

Wiggans, R.E.

White Rose Research Online

SHORT REPORTEpidemiology of occupational hypersensitivitypneumonitis; reports from the SWORDscheme in the UK from 1996 to 2015C M Barber,1 R E Wiggans,1 M Carder,2 R Agius21Health and Safety Laboratory,Centre for Workplace Health,Health and Safety Executive,Buxton, UK2Centre for Occupational andEnvironmental Health, TheUniversity of Manchester,Manchester, UKCorrespondence toDr C M Barber, Health andSafety Laboratory, Centre forWorkplace Health, Health andSafety Executive, Harpur Hill,Buxton SK17 9JN, UK;Chris.barber2@sth.nhs.ukReceived 11 May 2016Revised 13 July 2016Accepted 2 August 2016To cite: Barber CM,Wiggans RE, Carder M,et al. Occup Environ MedPublished Online First:[please include Day MonthYear] doi:10.1136/oemed-2016-103838ABSTRACTObjective To estimate the reported incidence ofoccupational hypersensitivity pneumonitis (OHP) in theUK and to consider whether the pattern of attributedcausation has changed over time.Methods All cases of OHP reported to the SWORDscheme between January 1996 and December 2015were classified into 1 of 10 categories of the suspectedagent. Cases were grouped into four 5-year timeperiods to examine any changing pattern in incidenceor suspected causation. For each time period, theannual incidence was calculated using the estimatednumber of reported cases and the working populationof the UK.Results Between 1996 and 2015, there were 202actual cases of OHP reported to SWORD, equating toan estimated 818 cases, when adjusting for thesampling ratio. Over this period, the annual UKincidence was 1.4 per million workers. The mean (SD)age of reported cases was 52 (13) years, and caseswere four-times more likely to be men than women.Over the study period, there was a fall in the proportionof cases reported to be due to agricultural exposures(44–12%), and an increase in cases due tometalworking fluids (MWFs, 2–45%).Conclusions Over the last 20 years, the incidence ofOHP in the UK has been ∼1–2 cases per millionworkers per year. Working with water-based MWFs isnow the most commonly suspected causative exposurefor OHP cases reported to the SWORD scheme inthe UK.INTRODUCTIONHypersensitivity pneumonitis (HP), also known asextrinsic allergic alveolitis, is a common form ofinterstitial lung disease,1 most commonly caused bydomestic or workplace exposures.2 There is clear evi-dence that prognosis can be improved in HP if acause can be identified, and further exposureavoided.3 Understanding the common sources ofworkplace exposure is therefore important to encour-age earlier recommendations of antigen avoidance byclinicians managing this condition in patients ofworking age. National reporting schemes offer valu-able data to assist in this. The aim of this study was toexplore the most commonly suspected causes ofoccupational hypersensitivity pneumonitis (OHP)reported to the UK SWORD surveillance scheme4and to consider whether these had changed overtime.METHODSAll cases of OHP reported to the SWORD scheme4between January 1996 and December 2015 wereclassified into 1 of 10 categories by the suspectedcausative agent. Cases were grouped into four5-year time periods to examine any changingpattern in incidence or suspected causation. Foreach time period, the estimated annual incidencewas calculated using the estimated number ofreported cases and the working population of theUK at that time as documented by the Office forNational Statistics (ONS).5RESULTSBetween 1996 and 2015, there were 202 actualcases of OHP reported to SWORD, equating to anestimated 818 cases (allowing for differences in thereporting frequency of ‘core’ and ‘sample’ repor-ters).4 Over this period, the annual UK incidencewas 1.4 per million workers (1.5 per million foreach of the first three 5-year time periods, and 1.2per million for 2011–2015). Reported cases wereconsistently more likely to be men than womenwith an overall ratio of ∼4:1, with 73–86% ofcases being men in each 5-year time period. TheWhat this paper adds▸ Although hypersensitivity pneumonitis (HP) is acommon form of interstitial lung diseaseinternationally, little is known about theepidemiology of the condition.▸ National reporting data offer a method ofbetter understanding the occupational causesof this disease and examining trends incausation with time.▸ The reported incidence of occupational HP inthe UK is ∼1–2 cases per million workers peryear, which is similar to estimates for a limitednumber of other countries.▸ Over the last 20 years, exposure to metalworkingfluids has been the most frequently reportedcausative agent for cases of occupational HPreported to the SWORD scheme in the UK.▸ Healthcare workers should be aware of the linkbetween occupation and HP and take asystematic occupational history when assessingsymptomatic workers.Barber CM, et al. Occup Environ Med 2016;0:1–3. doi:10.1136/oemed-2016-103838 1Practice OEM Online First, published on October 8, 2016 as 10.1136/oemed-2016-103838Copyright Article author (or their employer) 2016. Produced by BMJ Publishing Group Ltd under licence. group.bmj.com on December 14, 2016 - Published by http://oem.bmj.com/Downloaded from mean (SD) age of reported cases was 52 (13) years, which wasnot significantly different for men and women (52 vs 49 years,p=0.14). Eighty-three per cent of reported cases were over theage of 40, and 20 of these were over the age of 65 (two-thirdsof these were farmers).During the period studied, the commonest suspected causesof OHP in the UK were exposures to metalworking fluids(MWFs, 35%), farming (17%) and birds (11%). A wide rangeof occupations were reported to have been associated with OHPdue to avian exposures, most commonly related to poultryfarming and domestic bird breeding. Less commonly reportedcauses included contact with birds in pet shops, veterinary prac-tices and bird sanctuaries. Twelve per cent of cases were attribu-ted to other agents, and in 5% of cases respiratory physicianswere not able to identify the likely cause. The suspected causesof OHP between 1996 and 2015 per 5-year period are shownin figure 1.DISCUSSIONThis study has demonstrated that over the last 20 years, theoverall incidence of OHP in the UK has been ∼1–2 cases permillion workers per year. Over this time period, reported caseswere four times more likely to be men than woman. In terms ofsuspected causes, the proportion due to bird handling hasremained relatively stable, whereas there has been a fall inreported cases due to agricultural exposures. In marked contrast,the number of cases due to water-based MWFs has risen dra-matically, and this exposure is now the most commonly reportedcause.The limitations of estimating the incidence of work-relatedrespiratory disease from the SWORD data,6 examining trends inincidence7 and comparing this with data from other nationalreporting schemes have been discussed in detail elsewhere.8These relate to the potential underestimation of incidence ratesas not all chest physicians participate in the SWORD scheme,the potential for reporter fatigue over time and differences inthe design of national reporting schemes. The data used in thisstudy are based on voluntary reporting, and the SWORDscheme does not record information as to how the diagnosiswas confirmed or how the suspected agent was identified. Thetrue incidence of OHP is unknown, but it is likely to varybetween countries with different climates, types of industry,smoking prevalence and genetic factors. This study estimatedthe clinically reported UK incidence of OHP to be ∼1–2 permillion workers, which is lower than the 8 per million workersestimated for allergic occupational asthma (OA) over the sametime period. The relative incidence of these allergic lung dis-eases in the UK is significantly different from other nationalreporting schemes, where 25–30 cases of OA have beenreported for each case of OHP.9–11 International comparisonsare inherently difficult,8 and the reasons for this difference arenot apparent from our study. It is clear however that the UKestimate of the incidence of OHP is within the 0.4–2.7 permillion workers range that has been estimated by other report-ing schemes from Australia,9 Catalonia,10 the Czech Republic,12France and Germany.13 A higher estimate of 12.2 per millionworkers comes from the Finnish National Register,11 which mayrelate to the design of reporting schemes in different countries.Overall, SWORD estimates suggest that the incidence of OHPin the UK might be slowly falling, from 2 per million workersfor 1992–2000,4 1.5 per million for 1996–2010, to 1.2 permillion for 2011–2015. A similar fall has also been noted forthe 2000–2012 period for OA in the UK.8 Given the previouslyidentified limitations of the SWORD reporting scheme in identi-fying trends in incidence,7 it is not possible to tell whether thesechanges reflect a true fall in disease incidence or an apparent fallrelating to changes in reporting patterns. Of note, incidencedata from primary care (1991–2003) and mortality data fromthe ONS (1968–2008) for all cause HP in the UK have notnoted a significant fall.14 15 The annual incidence of all causeHP for the UK population has been estimated to be ∼9 casesper million, which is clearly higher than our estimate for OHP.It is not possible to ascertain how much of the total HP burdenis occupational however, as the degree of under-reporting ofOHP is not known, and all cause HP includes the working andnon-working population. This difference is however in keepingwith published case series of all cause HP, where significant pro-portions related to domestic bird exposures.2Over the period studied, the average age of reported cases ofOHP in the UK was 52, which is similar to the 57-year-old meanreported for incident cases of all cause HP14 and the 48-year-oldaverage age for OHP noted in Spain10 and the Czech Republic,12respectively. It is not possible to tell from the SWORD data whyOHP most commonly affects workers in this age group, althoughpossible contributing factors include long disease latency, delaysin diagnosis, smoking cessation and temporal changes in work-place exposures, roles or health surveillance. Very little is knownabout the latent period in OHP, with the limited available Czechdata suggesting that it varies widely in individuals, rangingbetween 0.2 and 40 years (median 12.5 years).12OHP in the UK more commonly affects men than women,with about 80% of reported cases being men. This is in contrastFigure 1 Suspected causes of OHPreported to SWORD 1996–2015 by thefive-year time period. MWFs,metalworking fluids; OHP, occupationalhypersensitivity pneumonitis.2 Barber CM, et al. Occup Environ Med 2016;0:1–3. doi:10.1136/oemed-2016-103838Practicegroup.bmj.com on December 14, 2016 - Published by http://oem.bmj.com/Downloaded from to the findings of a UK primary care study of all cause HP, whichfound an equal gender ratio.14 This male predominance is higherthan that has been reported in other countries10–12 and is likelyto reflect the demographics of the ‘at risk’ occupational groups.For example, data from 2008 recorded that 84% of farmers and89% of metalworking machine operatives in the UK were men.16Historically, the main occupations at risk of HP in the UKhave been agricultural workers and bird handlers.4 Over the last20 years, there has been a change in causation however, with anoverall reduction in cases from agricultural exposures, particu-larly for mushroom workers. Possible explanations for thisrelate to improvements in working practices and an overallreduction in numbers of UK workers in these trades. In contrastto this fall, there has been a dramatic emergence of MWF-HP,from a single case reported in the 1996–2000 time period to40–45% of all cases for the three more recent time periods.Although it is not possible to establish the reasons for thisincrease from the SWORD data, possible explanations includethe increased use of water-soluble MWF, an increased numberof cases found during outbreak investigations17 18 and anincreased awareness among reporting clinicians. This temporalchange in proportionate causation from the agricultural tometalworking sectors has not been noted in other Europeanreporting schemes.12 13 The majority of reported cases ofMWF-HP have occurred in workers manufacturing componentsfor cars and airplanes, as time-limited clusters of disease.17 OHPmay present in a number of ways, and clinicians should have ahigh index of suspicion not only when seeing symptomaticworkers employed in these sectors, but also in any case of HPin a patient of working age where a detailed occupational andenvironmental history is warranted. Recognising OHP is import-ant for an individual patient, but also has implications for otherexposed coworkers, especially as outbreaks of disease have beenreported.18Finally, in a small proportion of cases of OHP (overall 6%),respiratory clinicians were not able to identify a suspected causein the workplace. This stayed relatively stable over the studyperiod and is in keeping with the 3% figure reported from theCzech Republic.12 Continuing data collection through reportingschemes such as SWORD is important to help track temporaltrends in incidence, to determine circumstances of exposureassociated with a significant risk as well as to raise awareness ofpotential new causal agents.In summary, this study has demonstrated that over the last20 years, there has been a marked change in the causation ofOHP in the UK, with MWF now being the most commonly sus-pected aetiological agent.Acknowledgements The authors are grateful to all physicians who report toSWORD.Contributors CMB, MC and RA planned the study. CMB, REW and MCcontributed to data collection and analysis. All authors contributed to the writing,revision and approval of the final manuscript.Funding SWORD is supported by the Health and Safety Executive in Great Britain(contract number PRJ500).Competing interests None declared.Provenance and peer review Not commissioned; externally peer reviewed.Open Access This is an Open Access article distributed in accordance with theCreative Commons Attribution Non Commercial (CC BY-NC 4.0) license, whichpermits others to distribute, remix, adapt, build upon this work non-commercially,and license their derivative works on different terms, provided the original work isproperly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/REFERENCES1 Demedts M, Wells AU, Anto JM, et al. Interstitial lung diseases: an epidemiologicaloverview. Eur Respir J Suppl 2001;32:2s–16s.2 Lacasse Y, Selman M, Costabel U, et al,. HP Study Group. Clinical diagnosis ofhypersensitivity pneumonitis. Am J Respir Crit Care 2003;168:952–8.3 Fernández Pérez ER, Swigris JJ, Forssén AV, et al. Identifying an inciting antigen isassociated with improved survival in patients with chronic hypersensitivitypneumonitis. Chest 2013;144:1644–51.4 McDonald JC, Chen Y, Zekveld C, et al. Incidence by occupation and industry ofacute work related respiratory diseases in the UK, 1992–2001. Occup Environ Med2005;62:836–42.5 Office for National Statistics Time Series: Employment release date, 16 March 2016.http://www.ons.gov.uk/employmentandlabourmarket/peopleinwork/employmentandemployeetypes/timeseries/mgrz6 Carder M, McNamee R, Turner S, et al. Improving estimates of specialist-diagnosed,work-related respiratory and skin disease. Occup Med 2011;61:33–9.7 McNamee R, Carder M, Chen Y, et al. Measurement of trends in incidence ofwork-related skin and respiratory diseases, UK 1996–2005. Occup Environ Med2008;65:808–14.8 Stocks SJ, McNamee R, van der Molen HF, et al. Trends in incidence ofoccupational asthma, contact dermatitis, noise-induced hearing loss, carpal tunnelsyndrome and upper limb musculoskeletal disorders in European countries from2000 to 2012. Occup Environ Med 2015;72:294–303.9 Elder D, Abramson M, Fish D, et al. Surveillance of Australian workplace BasedRespiratory Events (SABRE): notifications for the first 3.5 years and validation ofoccupational asthma cases. Occup Med 2004;54:395–9.10 Orriols R, Costa R, Albanell M, et al. Members of the Malaltia OcupacionalRespiratòria (MOR) Group. Reported occupational respiratory diseases in Catalonia.Occup Environ Med 2006;63:255–60.11 Oksa P, Palo L, Saalo A, et al. Occupational diseases in Finland in 2012. New casesof recognized and suspected occupational diseases. Finnish Institute of OccupationalHealth, FIOH Bookstore, Topeliuksenkatu 41 a A, FI-00250 Helsinki, Finland.12 Fenclová Z, Pelclová D, Urban P, et al. Occupational hypersensitivity pneumonitisreported to the Czech National Registry of Occupational Diseases in the period1992–2005. Ind Health 2009;47:443–8.13 Quirce S, Vandenplas O, Campo P, et al. Occupational hypersensitivity pneumonitis:an EAACI position paper. Allergy 2016;71:765–79.14 Solaymani-Dodaran M, West J, Smith C, et al. Extrinsic allergic alveolitis: incidenceand mortality in the general population. QJM 2007;100:233–7.15 Hanley A, Hubbard RB, Navaratnam V. Mortality trends in asbestosis, extrinsicallergic alveolitis and sarcoidosis in England and Wales. Resp Med2011;105:1373–9.16 Office for National Statistics data. The sex gap: which jobs do men and women do.http://www.theguardian.com/news/datablog/2009/jun/03/gender (accessed Apr2016).17 Rosenman KD. Asthma, hypersensitivity pneumonitis and other respiratory diseasescaused by metalworking fluids. Curr Opin Allergy Clin Immunol 2009;9:97–102.18 Burton CM, Crook B, Scaife H, et al. Systematic review of respiratory outbreaksassociated with exposure to water-based metalworking fluids. Ann Occup Hyg2012;56:374–88.Barber CM, et al. Occup Environ Med 2016;0:1–3. doi:10.1136/oemed-2016-103838 3Practicegroup.bmj.com on December 14, 2016 - Published by http://oem.bmj.com/Downloaded from 2015the SWORD scheme in the UK from 1996 tohypersensitivity pneumonitis; reports from Epidemiology of occupationalC M Barber, R E Wiggans, M Carder and R Agius published online October 8, 2016Occup Environ Med  http://oem.bmj.com/content/early/2016/10/08/oemed-2016-103838Updated information and services can be found at: These include:References #BIBLhttp://oem.bmj.com/content/early/2016/10/08/oemed-2016-103838This article cites 15 articles, 8 of which you can access for free at: Open Accesshttp://creativecommons.org/licenses/by-nc/4.0/non-commercial. See: provided the original work is properly cited and the use isnon-commercially, and license their derivative works on different terms, permits others to distribute, remix, adapt, build upon this workCommons Attribution Non Commercial (CC BY-NC 4.0) license, which This is an Open Access article distributed in accordance with the CreativeserviceEmail alertingbox at the top right corner of the online article. Receive free email alerts when new articles cite this article. Sign up in theCollectionsTopic Articles on similar topics can be found in the following collections  (155)Other (41)Agriculture and farming (119)Open accessNoteshttp://group.bmj.com/group/rights-licensing/permissionsTo request permissions go to:http://journals.bmj.com/cgi/reprintformTo order reprints go to:http://group.bmj.com/subscribe/To subscribe to BMJ go to:group.bmj.com on December 14, 2016 - Published by http://oem.bmj.com/Downloaded from 

Epidemiology of occupational hypersensitivity pneumonitis; reports from the SWORD scheme in the UK from 1996 to 2015

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Epidemiology of occupational hypersensitivity pneumonitis; reports from the SWORD scheme in the UK from 1996 to 2015

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