Changes in prevalence of chronic obstructive pulmonary disease and asthma in the US population and associated risk factors

Transcription

1 Original Articl Changs in prvalnc of chronic obstructiv pulmonary disas and asthma in th US population and associatd risk factors Chronic Rspiratory Disas 2015, Vol. 12(1) ª Th Author(s) 2014 Rprints and prmission: sagpub.co.uk/journalsprmissions.nav DOI: / crd.sagpub.com Cara N Halldin 1,2, Brnt C Dony 1 and Eva Hnizdo 1 Abstract Chronic lowr airway disass, including chronic obstructiv pulmonary disas (COPD) and asthma, ar currntly th third lading caus of dath in th Unitd Stats. W aimd to valuat changs in prvalnc of and risk factors for COPD and asthma among th US adult population. W valuatd changs in prvalnc of slf-rportd doctor-diagnosd COPD (i.. chronic bronchitis and mphysma) and asthma and slf-rportd rspiratory symptoms comparing data from th and National Halth and Nutrition Examination Survys. To invstigat changs in th svrity of ach outcom ovr th two priods, w calculatd changs in th proportions of spiromtry-basd airflow obstruction for ach outcom. Prvalnc of doctor-diagnosd chronic bronchitis and mphysma dcrasd significantly mainly among mals, whil asthma incrasd only among fmals. Th slf-rportd disas and th rspiratory symptoms wr associatd with incrasd prvalnc of airflow obstruction for both priods. Howvr, th prvalnc of airflow obstruction dcrasd significantly in th scond priod among thos with shortnss of brath and doctor-diagnosd rspiratory conditions (chronic bronchitis, mphysma, and asthma). COPD outcoms and asthma wr associatd with lowr ducation, smoking, undrwight and obsity, and occupational dusts and fums xposur. Chronic lowr airway disass continu to b major public halth problms. Howvr, dcrasd prvalnc of doctor-diagnosd chronic bronchitis and mphysma (in mals) and dcrasd prvalnc of airflow obstruction in thos with rspiratory symptoms and doctor-diagnosd rspiratory disass may indicat a dclining trnd and dcras in disas svrity btwn th two priods. Continud focus on prvntion of ths disass through public halth intrvntions is prudnt. Kywords Chronic bronchitis, mphysma, asthma, occupational xposur, occupational disass, NHANES Introduction Asthma and chronic obstructiv pulmonary disas (COPD) ar common conditions charactrizd by airway obstruction. Asthma is markd by pisodic chst tightnss, whzing, coughing, and brathlssnss associatd with variabl and rvrsibl airflow obstruction. 1 COPD includs chronic bronchitis, dfind by th prsnc of rcurring symptoms of chronic productiv cough for a minimum of 3 months in two or mor conscutiv yars, and mphysma, charactrizd by dstruction of th alvolar walls and prmanntly nlargd trminal air spacs. 2 Airflow obstruction in COPD is not fully rvrsibl. 3 In 2008, dirct halth-car costs in th Unitd stats rlatd to COPD and asthma totald US$53.7 billion; indirct costs du to lost productivity amountd to an 1 Division of Rspiratory Disas Studis, National Institut for Occupational Safty and Halth, Cntrs for Disas Control and Prvntion, Morgantown, WV, USA 2 Epidmic Intllignc Srvic Program, Cntrs for Disas Control and Prvntion, Atlanta, GA, USA Corrsponding author: Cara N. Halldin, Division of Rspiratory Disas Studis, National Institut for Occupational Safty and Halth, 1095 Willowdal Road MS-HG900.2, Morgantown, WV 26505, USA. challdin@cdc.gov

2 48 Chronic Rspiratory Disas 12(1) additional US$14.3 billion. 4 Rcnt rports indicat that daths from chronic lowr airway disass, which includ COPD and asthma, ar on th ris and ar currntly th third lading caus of dath in th Unitd Stats. 5 Smoking is rcognizd as th primary caus of mphysma 6 and as th most common risk factor for chronic bronchitis and COPD; howvr, occupational and nvironmntal xposurs also contribut to th incrasd risk of ths disass. 6 8 Studis hav dmonstratd that occupational xposur can contribut to th dvlopmnt of small airways disas 9 and mphysma. 10,11 About 15% of COPD and 15% of asthma cass ar stimatd to b attributd to occupational xposurs Howvr, th contribution of occupational and nvironmntal xposurs to COPD and asthma is oftn difficult to discrn in individual patints; this applis spcially to COPD among smokrs. 17 Additionally, about 2% of COPD cass 18 ar associatd with a gntic mutation causing a 1 -antitrypsin dficincy. 19 Th most rcnt stimat of th prvalnc of rspiratory symptoms and doctor-diagnosd COPD and asthma in th US population using th National Halth and Nutrition Examination Survy (NHANES) was rportd using data from NHANES III ( ). 20,21 Estimatd prvalnc of COPD, among US adults agd 25 and oldr, was 15.1% basd upon lung function tsting by spiromtry and 5.2% basd upon doctor diagnosis of COPD (ithr chronic bronchitis, mphysma, or both). 22 Th stimatd prvalnc of doctor-diagnosd currnt asthma among thos 20 yars and oldr was 4.5%. Howvr, th prvalnc of whzing was highr, with a prvalnc of 16.4%. 23 Th most rcnt NHANES study includd a rspiratory componnt and provids an opportunity to valuat changs in th prvalnc of rspiratory symptoms and doctor-diagnosd obstructiv airway disass in th US population sinc and an opportunity to valuat th contribution of individual and occupational risk factors to chronic lowr airway disass. Th objctiv of our study was to invstigat trnds in th prvalnc of chronic lowr airway disas in th US population focusing on slf-rportd doctordiagnosd COPD and asthma, rspiratory symptoms, and airflow obstruction masurd by spiromtry. For this purpos, w compard prvalnc of ths disass and conditions using NHANES data obtaind from 1988 to 1994 and from 2007 to 2010 survys. In addition, w invstigatd th associations btwn occupational risk factors and chronic lowr airway disass (slf-rportd symptoms, slf-rportd doctor diagnosis, and airflow obstruction) using th most rcnt NHANES data. Mthods Study population NHANES is a sris of cross-sctional halth intrviw and halth xamination survys dsignd to slct and study a rprsntativ sampl of th US population and is conductd by th National Cntr for Halth Statistics at th Cntrs for Disas Control and Prvntion. Study participants compltd an intrviw followd by a physical assssmnt at a mobil xamination cntr. Participants answrd qustions about rspiratory symptoms and doctordiagnosd rspiratory disass. For this rport, w usd data collctd during and survys. Informd consnt was obtaind from all participants and th National Cntr for Halth Statistics Rsarch Ethics Rviw Board approvd th protocol. National Halth and Nutrition Examination Survy data ar publically accssibl from th US Cntrs for Disas Control and Prvntion National Cntr for Halth Statistics Wb sit Our study sampl was limitd to adults agd yars. Th survy classifid participants as non-hispanic Whit, non-hispanic Black, Mxican Amrican, or othr. Othr Hispanic was an additional rac/thnicity catgory addd in th survy. Variabl dfinition Slf-rportd symptoms Chronic Bronchitis. Participants wr considrd to hav symptoms of chronic bronchitis if thy rspondd affirmativly to th following qustions about chronic cough and chronic phlgm: Do you usually cough on most days for 3 conscutiv months or mor during th yar? ; Do you usually bring up phlgm on most days for 3 conscutiv months or mor during th yar? and rportd an answr gratr than or qual to 2 yars to th following qustions: For how many yars hav you had this cough? ; For how many yars hav you had this troubl with phlgm?. Whzing. No qustions wr askd consistntly btwn th two survys, which could dvlop a

3 Halldin t al. 49 cas dfinition for asthma basd upon diagnostic symptoms rcommndd by th National Asthma Education and Prvntion Program. 24 On qustion about whzing was consistntly askd in both survys, thrfor w rport on th prvalnc of rcnt whzing. Participants wr classifid as having symptoms of whzing if thy answrd affirmativly to Hav you had whzing or whistling in your chst at any tim in th past 12 months?. Shortnss of brath. A qustion xamining shortnss of brath on xrtion was also askd in both survys. Participants in th survy wr classifid as having shortnss of brath if thy rspondd affirmativly to Ar you troubld by shortnss of brath whn hurrying on lvl ground or walking up a slight hill?. Participants in th survy wr classifid as having shortnss of brath if thy rspondd affirmativly to Hav you had shortnss of brath ithr whn hurrying on th lvl or walking up a slight hill?. Slf-rportd doctor and/or halth profssional diagnosd conditions. Whn comparing th two survys, qustions assssing th prsnc of doctor-diagnosd conditions wr askd in a slightly diffrnt mannr. In th survy, participants wr askd Has a doctor vr told you that you had..., whras in th survy participants wr askd Has a doctor and/or othr halth profssional vr told you that you had... For simplicity purposs, w will rfr to rsponss from both survys rgarding diagnosd conditions as doctor-diagnosd. Doctor-diagnosd chronic bronchitis. Participants wr considrd to hav doctor-diagnosd chronic bronchitis if thy rspondd positivly to Has a doctor (and/ or halth profssional in th cas of th survy) vr told you that you had chronic bronchitis? and Do you still hav chronic bronchitis?. Doctor-diagnosd mphysma. Participants wr considrd to hav doctor-diagnosd mphysma if thy rspondd positivly to Has a doctor (and/or halth profssional in th cas of th survy) vr told you that you had mphysma?. Doctor-diagnosd asthma. Participants wr considrd to hav doctor-diagnosd currnt asthma if thy rspondd positivly to Has a doctor (and/or halth profssional in th cas of th survy) vr told you that you had asthma? and Do you still hav asthma?. Airflow obstruction. Th svrity of th slf-rportd symptoms of chronic bronchitis as wll as slfrportd doctor diagnoss of chronic bronchitis and mphysma wr compard for ach priod by valuating th prvalnc of airflow obstruction masurd by spiromtry. W usd th Amrican Thoracic Socity (ATS) critria of mild or wors (mildþ) airflow obstruction 25 dfind as th ratio of forcd xpiratory volum in 1 scond (FEV1) to th forcd vital capacity (FVC) lss than th lowr 5th prcntil (i.. lowr limit of normal (LLN) 26 ; FEV1/FVC < LLN). Modrat or wors (modratþ) airflow obstruction was dfind as FEV1/FVC < LLN plus FEV1 < 70% prdictd basd on th ATS critria. 25 Furthr dscriptions of mthods for spiromtry tsting, intrprtation, and dfining airflow obstruction hav bn dscribd prviously. 27 Dmographics Dmographic variabls and risk factors invstigatd wr ag, rac, ducation, smoking status, body mass indx (BMI), and occupational xposur. Smoking status was catgorizd by nvr smokrs (thos who had smokd lss than 100 cigartts in thir ntir lif), x-smokrs (thos who had smokd mor than 100 cigartts in thir ntir lif, but did not currntly smok), and currnt smokrs. Th pack-yars variabl was stimatd by multiplying currnt numbr of packs smokd by th numbr of yars th participant rportd smoking. For x-smokrs, pack-yars was dtrmind using th numbr of packs thy rportd smoking whn thy last smokd. Occupational variabls Occupational xposur variabls wr cratd from rsponss to th occupational qustionnair modul administrd in th survy. Participants btwn th ags 16 and 79 who indicatd that thy wr mployd, ithr currntly or at on point in thir livs, wr askd occupational xposur qustions. Occupational xposur to minral dust was classifid as an affirmativ answr to In any job, hav you vr bn xposd to dust from rock, sand, concrt, coal, asbstos, silica or soil?. Occupational xposur to organic dust was classifid as an affirmativ answr to In any job, hav you vr bn xposd to dust from baking flours, grains, wood, cotton, plants, or animals?. Occupational xposur to xhaust fums was classifid as an affirmativ answr to In any job, hav you vr bn xposd to xhaust

4 50 Chronic Rspiratory Disas 12(1) fums from trucks, buss, havy machinry, or disl ngins?. Occupational xposur to othr fums was classifid as an affirmativ answr to In any job, hav you vr bn xposd to any othr gass, vapors, or fums? Exampls ar vapors from paints, claning products, glus, solvnts, and acids; or wlding/soldring fums.. Ths variabls wr also combind into th following variabls vr dust and/or fum xposur, vr dust xposur, and vr fum xposur. Statistical data analysis Ag-standardizd prvalnc wr stimatd using Statistical Analysis Systm (SAS), vrsion 9.3 softwar, procdur PROC SURVEYREG, 28 which accountd for th study dsign and NHANES xamination wights assignd to ach participant. Ag standardization to th US population of 2000 was applid to th stimatd prvalnc for th and priods using national Currnt Population Survy population siz tabls Th wightd frquncis and mans wr drivd using SAS procdur PROC SURVEYFREQ and PROC SURVEY- MEANS, accounting for th study dsign and xamination wights. To compar th prvalnc stimats from NHANES and , PROC SURVEYLOGISTIC was usd to calculat th Wald statistic and p valus valuation if th distribution of dmographic charactristics btwn th two tim priods was statistically diffrnt. PROC SUR- VEYREG was usd to calculat a t statistic and assss whthr th man pack-yars among smokrs in th two survy priods was statistically diffrnt. Dmographic-spcific prvalnc of symptoms of chronic bronchitis, whzing, and shortnss of brath, as wll as doctor-diagnosd mphysma, chronic bronchitis, and asthma, wr calculatd for both survy priods. Additionally, ag-standardizd prvalnc of ATS mildþ and modratþ airflow obstruction according to th prsnc or absnc of rspiratory symptoms or doctor-diagnosd rspiratory disass was calculatd for th participants who compltd spiromtry tsting. Multipl logistic rgrssion using PROC SURVEYLOGISTIC was usd to stimat odds ratios (ORs) (and 95% confidnc intrvals (CIs)) for th association of rspiratory symptoms, as wll as doctor-diagnosd chronic bronchitis, mphysma, and asthma and airflow obstruction with ducation, smoking status, BMI, and slf-rportd occupational xposur to dusts and fums, adjusting for th ffct of ag, sx, and rac, for NHANES rspondnts who rportd vr mploymnt. Rsults Tabl 1 shows dscriptiv statistics for NHANES and NHANES participants agd In this ag rang, man ag (55.8 vs yars, p ¼ 0.32) and ag distribution wr similar for th two study sampls. Proportions of mals and fmals sampld in th two survys wr not statistically diffrnt (p ¼ 0.22). Compard to th survy, th sampl had a highr proportion of non-hispanic Black and Mxican Amrican participants and had a significantly highr lvl of ducation rportd among participants (som collg 16.8% vs. 27.5%.; collg graduat 21.3% vs. 27.9%; p < ). Th man BMI was significantly highr in th survy (27.4 vs kg/m 2 ; p < ). Th frquncy of obsity, dfind as BMI of 30 kg/m 2 or gratr, incrasd by narly 10 prcntag points in (27.2% vs. 37.7%; p < ). Convrsly, th proportion of participants with normal BMI ( kg/m 2 ) dcrasd by almost th sam amount in (34.8% vs. 25.1%; p < ). Th sampl had a significantly highr proportion of nvr smokrs (39.9% vs.51.2%; p < ) and significantly dcrasd man pack-yars of smoking (29.4 vs packyars; p < ) whn th x-smokr and currnt smokr catgoris wr combind. Ag-standardizd stimatd prvalnc of symptoms of chronic bronchitis (Tabl 2) did not diffr significantly btwn th two sampl priods among any of th dmographic catgoris. Significant dcrass in th stimatd prvalnc of whzing wr obsrvd among svral dmographic catgoris in (ags 40 79, mals, non-hispanic Whits, Mxican Amricans, and currnt smokrs (data not shown)). Prvalnc of shortnss of brath significantly incrasd in among non-hispanic Blacks but dcrasd among Mxican Amricans. Ag-standardizd stimatd prvalnc of doctordiagnosd conditions is summarizd in Tabl 3. Prvalnc of doctor-diagnosd chronic bronchitis dcrasd significantly in ovrall and spcifically among svral dmographic catgoris (ags and 70 79, mals, non-hispanic Whits, Mxican Amricans, and currnt smokrs (data not shown)). Prvalnc of doctor-diagnosd mphysma

5 Halldin t al. 51 Tabl 1. Dscriptiv statistics for NHANES and NHANES data for yar-olds. a Dmographic data NHANES NHANES Sampl n Population N (thousand) b Wightd prcnt Sampl n Population N (thousand) b Wightd prcnt Ovrall , ,199 Ag (yars) , , , , , , , , Gndr Mals , , Fmals , , Rac NH Whit , , NH Black , Mxican Amrican Othr Hispanic N/A N/A Othr Education <High school High school Som collg Collg grad BMI < Smoking status Nvr smokr Ex-smokr Currnt smokr Pack-yars (n, man (SE)) c Ex-smokr þ currnt smokr (0.54) (1.01) NHANES: National Halth and Nutrition Examination Survy; NH: non-hispanic; N/A ¼ data not availabl; BMI: body mass indx. a Othr Hispanic classification was not availabl in NHANES III. b Currnt Population Survy. c Data prsntd as man pack-yars with standard rror in brackts. rmaind stabl btwn th two sampl priods, xcpt for mals whr th prvalnc dcrasd significantly in (4.7% vs. 2.7%; p < 0.001). Th prvalnc of doctor-diagnosd currnt asthma significantly incrasd in ovrall and among svral dmographic catgoris (ags 60 69, 70 79, fmals, non-hispanic Whits, non-hispanic Blacks, and among nvr smokrs, x-smokrs, and currnt smokrs). From th survy, 90% of thos agd and from th survy 77% of thos agd had valid spiromtry and sufficint biomtric data to valuat lung function. 27 Tabl 4 shows th prvalnc of mildþ and modratþ airflow obstruction masurd by spiromtry, as dfind by ATS critria, for th two study priods, by th prsnc of rspiratory symptoms, and doctor-diagnosd rspiratory disass among individuals agd yars. For xampl, among thos with doctordiagnosd mphysma in th survy, 59.41% had mildþ airflow obstruction. Convrsly, among thos who did not rport a doctor diagnosis

6 Tabl 2. Th US population ag-standardizd prvalnc of slf-rportd rspiratory symptoms among ags 40 79, and a Slf-rportd symptoms of chronic bronchitis b Slf-rportd whzing b Slf-rportd shortnss of brath b t tst of (n ¼ 9610) c (n ¼ 7289) c diffrnc t Tst of (n ¼ 9610) c (n ¼ 7293) c diffrnc t Tst of (n ¼ 9580) c (n ¼ 7288) c diffrnc p d (SE) p (SE) p Valu p (SE) p (SE) p Valu p (SE) p (SE) p Valu Ovrall 4.6 (0.37) 4.7 (0.40) 17.4 (0.52) 14.3 (0.75) (0.89) 30.5 (0.96) Ag (0.53) 4.3 (0.49) 17.5 (1.07) 14.6 (0.89) (1.13) 27.9 (1.06) (0.39) 5.3 (0.44) 17.2 (0.68) 13.6 (1.08) (1.29) 35.6 (1.28) Gndr Mals 5.7 (0.49) 5.7 (0.55) 17.9 (0.98) 14.0 (0.91) (1.19) 26.5 (1.08) Fmals 3.6 (0.45) 3.7 (0.43) 17.0 (0.96) 14.5 (0.87) 31.9 (1.29) 34.2 (1.12) Rac NH Whit 5.0 (0.44) 5.3 (0.48) 18.0 (0.93) 14.5 (0.90) (1.11) 31.2 (1.19) NH Black 3.0 (0.29) 3.5 (0.59) 15.2 (1.09) 17.8 (1.54) 30.4 (1.19) 35.4 (1.64) 0.05 Mxican Amrican 2.3 (0.36) 2.0 (0.40) 15.1 (1.28) 8.8 (0.70) (1.37) 24.5 (1.23) 0.05 Othr Hispanic N/A 2.8 (0.56) N/A 10.5 (0.94) N/A 26.7 (1.77) Othr 3.7 (1.63) 3.8 (1.13) 14.1 (2.05) 13.2 (2.75) 25.9 (3.13) 22.6 (3.04) N/A: data not availabl. a Th Othr Hispanic classification was not availabl in NHANES III. Comparisons could not b mad bcaus th othr Hispanic classification was not availabl in NHANES III. b S Mthods sction in th corrsponding sctions for dfinition. c Population agd that had a valid rspons to rspctiv rspiratory symptoms qustions. d Ag-wightd and ag-standardizd wightd prvalnc. Comparisons could not b mad bcaus th Othr Hispanic classification was not availabl in NHANES III. 52

7 Tabl 3. Th US population ag-standardizd prvalnc of slf-rportd doctor-diagnosis among prsons yars, and a Doctor-diagnosd chronic bronchitis b Doctor-diagnosd mphysma b Doctor-diagnosd currnt asthma b t tst of (n ¼ 9614) c (n ¼ 7276) c diffrnc t tst of (n ¼ 9612) c (n ¼ 7284) c diffrnc t tst of (n ¼ 9614) c (n ¼ 7289) c diffrnc p d (SE) p (SE) p valu p (SE) p (SE) p Valu p (SE) p (SE) p Valu Ovrall 5.0 (0.37) 3.2 (0.46) (0.28) 2.7 (0.24) 5.3 (0.40) 7.9 (0.58) Ag (0.49) 2.5 (0.41) (0.29) 1.6 (0.19) 5.6 (0.58) 7.5 (0.75) (0.45) 4.7 (0.66) (0.58) 4.8 (0.52) 4.9 (0.35) 8.6 (0.59) Gndr Mals 4.3 (0.43) 2.1 (0.43) (0.43) 2.7 (0.34) (0.51) 5.7 (0.67) Fmals 5.7 (0.58) 4.3 (0.61) 2.5 (0.28) 2.6 (0.26) 5.8 (0.53) 9.9 (0.75) Rac NH Whit 5.3 (0.45) 3.5 (0.59) (0.32) 3.0 (0.30) 5.2 (0.43) 8.0 (0.75) NH Black 3.8 (0.33) 3.8 (0.65) 1.7 (0.25) 2.2 (0.35) 6.0 (0.56) 10.3 (1.10) Mxican Amrican 3.7 (0.56) 1.3 (0.29) (0.18) 0.5 (0.19) 4.3 (0.78) 3.1 (0.44) Othr Hispanic N/A 2.1 (0.41) N/A 2.0 (0.48) N/A 7.2 (0.63) Othr 4.8 (1.96) 2.0 (0.90) (1.84) 2.3 (0.76) 7.2 (2.14) 7.2 (1.53) N/A: data not availabl; NH: non-hispanic. a Th Othr Hispanic classification was not availabl in NHANES III. b S Mthods sction in th corrsponding sctions for dfinition. c Population agd that had a valid rspons to rspctiv doctor-diagnosd rspiratory conditions. d Ag-wightd and ag-standardizd wightd prvalnc. 53

8 54 Chronic Rspiratory Disas 12(1) Tabl 4. Th US population ag-standardizd prvalnc of airflow obstruction according to th prsnc or absnc of slf-rportd rspiratory symptoms and disass among prsons yars with valid spiromtry. Prvalnc of Mildþ ATS Prvalnc of Modratþ ATS a b a b P c (SE) N P (SE) N p Valu P (SE) N P (SE) N p Valu Ovrall 16.6 (0.8) (0.71) (0.45) (0.39) Symptoms of chronic bronchitis d No symptoms (0.73) (0.67) (0.44) (0.39) 5226 Symptoms (3.63) f (3.38) f (3.64) f (2.48) f 245 Symptoms of whzing d No symptoms (0.70) (0.67) (0.35) (0.26) 4750 Symptoms (1.94) f (2.20) f (1.35) f (1.47) f 724 Symptoms of shortnss of brath d No symptoms (0.75) (0.75) (0.39) (0.28) 3785 Symptoms (1.29) f (1.08) f (0.86) f (0.89) f Doctor-diagnosd chronic bronchitis d No (0.73) (0.71) (0.40) (0.38) 5302 Ys (3.17) f (4.82) g (3.06) f (3.61) f 161 Doctor-diagnosd mphysma d No (0.75) (0.69) (0.41) (0.37) 5361 Ys (5.29) f (4.28) f (4.46) f (4.66) f 106 Doctor-diagnosd asthma d No (0.70) (0.73) (0.39) (0.39) 5086 Ys (4.15) f (2.84) f (3.09) f (1.83) f ATS: airflow obstruction. a NHANES III ( ) total participation with valid data n ¼ 20,050. b NHANES total participation with valid data n ¼ 20,686. c Ag-wightd and ag-standardizd wightd prvalnc. d S Mthods sction for dfinition. Significant at a ¼ f Prvalnc of airflow obstruction in thos with slf-rportd symptoms/doctor-diagnosd condition ar significantly highr than thos without symptoms/condition among th sam survy priod at a ¼ g Prvalnc of airflow obstruction in thos with slf-rportd symptoms/doctor-diagnosd condition ar significantly highr than thos without symptoms/condition among th sam survy priod at a ¼ of mphysma during th sam priod, 15.13% had mildþ airflow obstruction. Ovrall, th prvalnc of mildþ and modratþ airflow obstruction significantly dcrasd in Tabl 4 also dmonstrats that th prsnc of slf-rportd rspiratory symptoms and doctor-diagnosd disas (chronic bronchitis, mphysma, and asthma) was significantly associatd with incrasd prvalnc of airflow obstruction as dtrmind by spiromtry for both priods. Howvr, th prvalnc of mildþ and modratþ airflow obstruction dcrasd significantly among thos with shortnss of brath and th doctor-diagnosd conditions of chronic bronchitis, mphysma, and asthma in Tabl 5 shows associations (OR) btwn slctd risk factors and chronic lowr airways disas. Th associations with lowr ducation, currnt and x-smoking status, and BMI outsid th rang of kg/m 2 (normal þ ovrwight BMI catgoris) showd an incrasing trnd. Participants rporting occupational xposur had significantly highr odds of all rspiratory symptoms and doctordiagnosd conditions than participants not rporting xposur. In particular, thos rporting vr dust and/ or fum xposur and vr dust xposur had twic th odds of chronic bronchitis symptoms compard with thos not rporting ths xposurs (vr dust and/or fum xposur OR ¼ 2.03, 95% CI: ; vr

9 Tabl 5. Association btwn risk factors and slf-rportd rspiratory symptoms, slf-rportd doctor-diagnosd conditions, and airflow obstruction among yar-olds, NHANES Symptoms Doctor-diagnosd conditions Airflow obstruction Chronic bronchitis Whzing Shortnss of brath Chronic bronchitis Emphysma Asthma ATS mildþ NHANES OR a 95% CI OR 95% CI OR 95% CI OR 95% CI OR 95% CI OR 95% CI OR 95% CI Education <High school High school Som collg Collg grad Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Smoking status Nvr smokr Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Ex-smokr Currnt smokr BMI < Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf. Rf > Occupational xposurs Evr dust and/or fum xposur b Evr dust xposur b Evr fums xposur b Exhaust fum xposur b ATS: Amrican Thoracic Socity; NHANES: National Halth and Nutrition Examination Survy; OR: odds ratio; BMI: body mass indx; Rf.: rfrnt group. a Adjustd for ag, gndr, rac, body mass indx, ducation lvl, smoking status, and pack-yars of smoking. b For comparison purposs, th rfrnt groups ar thos who wr nvr xposd. 55

10 56 Chronic Rspiratory Disas 12(1) dust xposur OR ¼ 2.13 CI: ). Thr wr no significant associations btwn occupational xposur and airflow obstruction. Participants who rportd occupational xhaust fum xposur had 20% gratr odds of airflow obstruction than othr participants, but this diffrnc did not rach statistical significanc. Discussion Our objctivs wr to invstigat whthr thr was a chang in th prvalnc of COPD and asthma outcoms and/or a chang in th svrity of th conditions as rflctd by th prsnc of airflow obstruction ovr tim and valuat th ffct of individual and occupational risk factors on th prvalnc of ths conditions. Summary of main findings To xplain changs in disas prvalnc btwn th two survys, w valuatd th changs in prvalnc of individual risk factors such as smoking, BMI, and ducation ovr th two priods. W found dcrasd prvalnc of currnt smoking (p < ) and dcrasd man pack-yars (p < ) among smokrs in th survy. Prvalnc of obsity (BMI > 30 kg/m 2 ) incrasd by mor than 10% (p <0.0001), whil corrspondingly th prvalnc of th normal BMI catgory (BMI kg/m 2 ; p <0.0001) dcrasd. In th survy, ovr 62% of th population rportd complting som high school or graduating from high school; howvr, in th survy a majority rportd attnding som collg or graduating from collg (55%; p <0.0001). Occupational risk factors wr valuatd using qustions askd during th survy about occupational dust and fum xposur among participants who rportd thy had vr workd. W found significantly incrasd ORs for th association btwn xposur to dusts and fums and almost vry rspiratory symptom and doctor-diagnosd rspiratory condition catgory. Most notably, th OR for vr dust xposur among thos with chronic bronchitis was 2.13 (CI: ). Intrstingly, significant rlationships btwn occupational xposur and airflow obstruction wr not obsrvd. Howvr, it is possibl that this could b attributd to th halthy workr ffct. 32 Prvious rsarch has suggstd that workrs who tak up and rmain in jobs with xposur to dusts and othr rspiratory irritants tnd to hav incrasd initial lvls of lung function whn compard to workrs who do not work in ths conditions. 33,34 Disas-spcific findings and rlations to th litratur Chronic bronchitis. Chronic bronchitis was valuatd using two outcoms. Th first outcom was th prsnc of chronic bronchitis symptoms as ascrtaind using a standard ATS-rcommndd dfinition and qustions on chronic cough and phlgm. Th scond outcom was th slf-rportd doctor-diagnosd chronic bronchitis, also ascrtaind by qustionnair. Prvalnc of chronic bronchitis symptoms did not chang btwn th two survys; howvr, w obsrvd a dcras in th prvalnc of slfrportd doctor diagnosis of chronic bronchitis. Chronic bronchitis is a potntially disabling condition, and both outcoms wr associatd with highr prvalnc of mild and modrat airflow obstruction. For both priods, th prvalnc of airflow obstruction (mildþ) was highr for thos who rportd chronic bronchitis symptoms than for th doctordiagnosd chronic bronchitis, suggsting a substantial proportion of thos with obstructiv chronic bronchitis may b undiagnosd. Howvr, whn comparing th two survys w obsrvd a dcras in th prvalnc of mildþ airflow obstruction in among thos with symptoms and/or doctordiagnosd chronic bronchitis, which may indicat a dcras in disas svrity btwn th two priods (Tabl 2). Additionally, significant dcrass in th prvalnc of doctor-diagnosd chronic bronchitis wr obsrvd among all ag-groups and spcifically among mals, non-hispanic Whits and Mxican Amricans. Evn though w hav obsrvd a dcras in th prvalnc of doctor-diagnosd chronic bronchitis, th fact that prvalnc of slf-rportd symptoms of chronic bronchitis has not changd sinc th NHANES III survy indicats that chronic bronchitis is still a major rspiratory illnss in th oldr US population. Howvr, it is unclar whthr factors lik ovrrporting of symptoms by individuals or undrdiagnosis by halthcar profssionals ar affcting th prvalnc of rportd disas. Smoking is th most common risk factor for chronic bronchitis, and w obsrvd that currnt smokrs had highr odds of chronic bronchitis than othrs (OR ¼ 4.97, CI: ; Tabl 5). Smoking rats dcrasd btwn th two survys which may hav contributd to th rducd prvalnc of doctordiagnosd chronic bronchitis and th rducd prvalnc of airflow obstruction in thos with th disas. Howvr, smoking is not th only risk factor for

11 Halldin t al. 57 chronic bronchitis. W obsrvd highr odds of chronic bronchitis for thos with lowr ducation status (OR ¼ 2.00, CI: ) and thos who wr undrwight (BMI < 18.5 kg/m 2 ;OR¼ 2.35, CI: ) or svrly obs (BMI > 35 kg/m 2 ; OR ¼ 1.54, CI: ), in modls that includd smoking (Tabl 5). Incrass in symptoms of chronic bronchitis hav bn dmonstratd among workrs with xposur to dusts (biologic and minral dust), gas, and fums COPD and airflow obstruction ar also associatd with xposur to biologic and minral dusts, gass, and fums 41 as wll as working in spcific industris (i.., rubbr, plastic, lathr, txtil, food products manufacturing, halth car, sals, construction, smlting, and agricultur). 42,43 W obsrvd that individuals with chronic bronchitis symptoms had th highst odds of xposur to dusts and fums compard with all othr rspiratory symptoms and conditions valuatd. Evr dust and/or fum and vr dust xposurs had among th highst ORs with 2.03 (CI: ) and 2.13 ( ), rspctivly. This suggsts that workrs continu to b xposd to dusts and fums at concntrations or at frquncis that ar ngativly impacting thir rspiratory halth. Futur rsarch should focus on furthr idntifying spcific jobs at risk for xposurs and chronic bronchitis. Emphysma. W found that th ovrall prvalnc of doctor-diagnosd mphysma dcrasd only in mals. Smoking is th primary risk factor for mphysma. Not surprisingly w obsrvd a strong association btwn doctor-diagnosd mphysma and bing a smokr or x-smokr (ORs ¼ and 5.68, Tabl 5). Th significantly rducd prvalnc of doctordiagnosd mphysma in mals may b du to th significant rduction in smoking rats and man pack-yars. In addition, rducd prvalnc of mildþ airflow obstruction was obsrvd among thos with mphysma, suggsting a rduction in disas svrity. Evn though smoking is rgardd as th major risk factor for mphysma, occupational risk factors hav bn idntifid. Emphysma, causd by inhalation of dust, spcially among coal and gold minrs, is wll documntd. 10,44 49 Furthrmor, tobacco smoking, whn combind with vapors, gass, dusts, and/or fums, has bn shown to hav, at a minimum, an additiv ffct whn contributing to th dvlopmnt of COPD 38 and mphysma alon. 38,45 Consistnt with th publishd litratur, w obsrvd significant incrasd odds for xposur to dusts and/or fums among thos with doctor-diagnosd mphysma (ORs rang ) whn adjusting for smoking. Asthma Intrstingly, w obsrvd a dcrasing prvalnc of symptoms for whzing but incrasing prvalnc of doctor-diagnosd asthma btwn th two survy priods. Significant dcrass in whzing wr obsrvd among almost vry ag catgory, among mals, and among non-hispanic Whits and Mxican Amricans. Convrsly, incrass in doctordiagnosd asthma wr obsrvd among vry ag catgory, among fmals, non-hispanic Whits and Blacks. This invrs rlationship suggsts that potntially mor asthmatic individuals ar sking car and bing diagnosd and thrfor ar potntially rciving appropriat tratmnt to rduc thir whzing symptoms. Th obsrvd incrasd prvalnc of doctor-diagnosd asthma could also b potntially influncd by th incras in awarnss of asthma among halthcar profssionals and thir patints Howvr, du to th limitd natur of th survy qustions askd and bcaus th qustions changd slightly btwn th two survy priods, it is unclar what xactly is driving this invrs obsrvation. Individual factors may b contributing to th incrasd prvalnc of doctor-diagnosd asthma. Obsity, considrd BMI gratr than 30 kg/m 2,has bn associatd with an incrasd prvalnc of asthma W found that individuals from th survy with asthma had an incrmntally and significantly incrasd ORs for obsity (BMI of kg/m 2 ;OR¼ 1.63) and svr obsity (BMI >35kg/m 2 ;OR¼ 2.04) compard to BMI kg/m 2. Thrfor, th incras in prvalnc of obsity w obsrvd in th survy is potntially contributing to th incrasd prvalnc of doctor-diagnosd asthma during th sam tim priod. Incrasd asthma prvalnc and symptoms of whzing hav prviously bn associatd with occupational dust and gas xposur. 40,56,57 W obsrvd occupational xposurs to dusts and fums to hav an ffct on th prvalnc of doctor-diagnosd asthma with th most substantial xposur catgory bing th aggrgatd vr dusts and/or fums catgory (OR ¼ 1.27; CI: ). Howvr, xposur to dusts and fums had a mor substantial ffct on th prvalnc of whzing with th aggrgatd vr dusts and/or fums catgory having th highst OR (OR ¼ 1.88 CI: ).

12 58 Chronic Rspiratory Disas 12(1) Strngths and limitations NHANES is a comprhnsiv, nationally rprsntativ study, dsignd to assss th halth status of th US population. Thrfor, utilization of NHANES data for this study is a strngth. This study is subjct to svral limitations. All information on survy participant s symptoms and doctor-diagnosd rspiratory disass was slf-rportd and subjct to rcall bias and misclassification. Intnsiv fforts to incras awarnss of COPD symptoms, diagnosis, and disas managmnt wr startd in th 1990s. 58 This incrasd awarnss may hav affctd diagnoss of COPD in th gnral US population and thus impactd prvalnc stimats in our study. Furthrmor, as mntiond prviously, awarnss of asthma also incrasd btwn th two survy priods which could hav contributd to th incrasd prvalnc of doctor-diagnosd asthma w obsrvd. In th survy, th phras and/or halth profssional was addd to qustions that was prviously askd about doctor-diagnosd conditions. It is possibl that this addition may hav changd how diagnosd conditions wr rportd by participants in th survy. Occupational xposurs wr slf-rportd. Individuals may b mor likly to rcall xposurs if thy hav rspiratory symptoms or a doctordiagnosd rspiratory disas. Furthrmor, th lack of associations btwn occupational xposurs and airflow obstruction may b du to th halthy workr ffct. Workrs, in gnral, tnd to b halthir, fittr, and hav incrasd lung function compard to nonworkrs in th sam population. This is spcially tru for workrs with occupational xposurs to dust. 33,34 In conclusion, th rsults of this study provid an updat on prvalnc of chronic rspiratory symptoms and doctor-diagnosd chronic lowr airway disass in th Unitd Stats. Th public halth implications of this study ar highlightd by th findings that from th to th survy priod, prvalnc of chronic bronchitis symptoms and doctor-diagnosd mphysma wr gnrally stabl, doctor-diagnosd chronic bronchitis and slf-rportd whzing dcrasd and doctordiagnosd asthma incrasd. Furthr vidnc for th association btwn occupational dust and fum xposur and chronic lowr airway disass and symptoms is providd. This study dmonstrats that COPD and asthma continu to b major public halth problms and mphasizs individual and occupational risk factors that could b targtd in fforts to prvnt and rduc th prvalnc of chronic lowr airway disass. Acknowldgmnts Th authors thank Grtchn Whit and Drs Kristin Cummings and Eiln Story for providing hlpful commnts and critiqu of th manuscript and Dr Lu-Ann Bckman-Wagnr for ovrsing training, data collction, and quality assuranc of spiromtry data. Agncy Disclaimr Th findings and conclusions of this rport ar thos of th authors and do not ncssarily rprsnt th viws of th Unitd Stats Cntrs for Disas Control and Prvntion National Institut for Occupational Safty and Halth. Authors Not CH and EH concivd th study. CH, BD, and EH analyzd th data and intrprtd th rsults. CH, BD, and EH wrot th manuscript. All authors hav rad and approvd th final manuscript. Funding This work was prformd by US Fdral Govrnmnt mploys as part of thir work; no non-govrnmntal funding supportd this work. Th Cntrs for Disas Control and Prvntion National Institut for Occupational Safty and Halth supportd th salaris of th authors. Rfrncs 1. Batman E, Hurd S, Barns P, t al. Global stratgy for asthma managmnt and prvntion: GINA xcutiv summary. Eur Rspir J 2008; 31(1): Snidr G. Th dfinition of mphysma: rport of a National Hart, Lung and Blood Institut Division of Lung Disass Workshop. Am Rv Rspir Dis 1985; 132: Clli BR, MacN W and ATS/ERS Task Forc. Standards for th diagnosis and tratmnt of patints with COPD: a summary of th ATS/ERS position papr. Eur Rspir J 2004; 23(6): U.S. Dpartmnt of Halth and Human Srvics. National Instituts of Halth. National Hart Lung and Blood Institut. Morbitiy and Mortality: 2012 Chartbook on Cardiovascular, Lung, and Blood Disass Hoyrt DL and Xu J. Daths: prliminary data for Natl Vital Stat Rp 2012; nvsr/nvsr61/nvsr61_06.pdf (accssd 9 Dcmbr 2014). 6. U.S. Dpartmnt of Halth and Human Srvics. Th halth consquncs of smoking: a rport of th surgon gnral. Atlanta: U.S. Dpartmnt of Halth and

13 Halldin t al. 59 Human Srvics, Cntrs for Disas Control and Prvntion, National Cntr for Chronic Disas Prvntion and Halth Promotion, Offic of Smoking and Halth, Lindbrg A, Jonsson AC, Ronmark E, t al. Tn-yar cumulativ incidnc of COPD and risk factors for incidnt disas in a symptomatic cohort. Chst 2005; 127(5): Lang P, Groth S, Nybo J, t al. Chronic obstructiv lung disas in Copnhagn: cross-sctional pidmiological aspcts. J Intrn Md 1989; 226(1): Wang ML, Bckman-Wagnr LA, Wolf AL, t al. Lung-function impairmnt among US undrground coal minrs, 2005 to 2009: gographic pattrns and association with coal workrs pnumoconiosis. J Occup Environ Md 2013; 55(7): Hnizdo E, Murray J and Davison A. Corrlation btwn autopsy findings for chronic obstructiv airways disas and in-lif disability in South African gold minrs. Int Arch Occup Environ Halth 2000; 73(4): Hnizdo E, Sluis-Crmr GK and Abramowitz JA. Emphysma typ in rlation to silica dust xposur in South African gold minrs. Am Rv Rspir Dis 1991; 143(6): Balms J, Bcklak M, Blanc P, t al. Amrican Thoracic Socity Statmnt: Occupational contribution to th burdn of airway disas. Am J Rspir Crit Car Md 2003; 167(5): Torn K and Blanc PD. Asthma causd by occupational xposurs is common a systmatic analysis of stimats of th population-attributabl fraction. BMC Pulm Md 2009; 9: Blanc PD and Torn K. Occupation in chronic obstructiv pulmonary disas and chronic bronchitis: an updat. Int J Tubrc Lung Dis 2007; 11(3): Bang KM, Syamlal G, Mazurk JM, t al. Chronic obstructiv pulmonary disas prvalnc among nonsmokrs by occupation in th Unitd Stats. J Occup Environ Md 2013; 55(9): Hnizdo E, Sullivan PA, Bang KM, t al. Association btwn chronic obstructiv pulmonary disas and mploymnt by industry and occupation in th US population: a study of data from th Third National Halth and Nutrition Examination Survy. Am J Epidmiol 2002; 156(8): Fishwick D, Darby A, Hnizdo E, t al. COPD causation and workplac xposurs: an assssmnt of agrmnt among xprt clinical ratrs. COPD: J Chron Obstruct Pulmon Dis 2013; 10(2): Librman J, Wintr B and Sastr A. Alpha 1-antitrypsin pi-typs in 965 COPD patints. Chst 1986; 89(3): Eriksson S. Pulmonary mphysma and alpha-1- antitrypsin dficincy. Acta Md Scand 1964; 175(2): Mannino DM, Gagnon RC, Ptty TL, t al. Obstructiv lung disas and low lung function in adults in th Unitd Stats: data from th National Halth and Nutrition Examination Survy, Arch Intrn Md 2000; 160(11): Hnizdo E, Glindmyr HW, Ptsonk EL, t al. Cas dfinitions for chronic obstructiv pulmonary disas. COPD: J Chron Obstruct Pulmon Dis 2006; 3(2): Mannino DM, Homa DM, Akinbami LJ, t al. Chronic obstructiv pulmonary disas survillanc Unitd Stats, MMWR Survill Summ 2002; 51(6): Arif AA, Dlclos GL, L ES, t al. Prvalnc and risk factors of asthma and whzing among US adults: an analysis of th NHANES III data. Eur Rspir J 2003; 21(5): National Instituts of Halth. Exprt Panl Rport 3: Guidlins for th Diagnosis and Managmnt of Asthma, publication no Bthsda: National Instituts of Halth/National Hart, Lung, and Blood Institut, Pllgrino R, Vigi G, Brusasco V, t al. Intrprtativ stratgis for lung function tsts. Eur Rspir J 2005; 26(5): Hankinson JL, Odncrantz JR and Fdan KB. Spiromtric rfrnc valus from a sampl of th gnral U.S. population. Am J Rspir Crit Car Md 1999; 159(1): Dony B, Hnizdo E, Dillon C, t al. Prvalnc of airflow obstruction in U.S. adults agd yars: NHANES data and COPD. Epub ahad of print 22 Sptmbr DOI: / SAS Institut Inc. Bas SAS 9.3 Procdurs Guid: Statistical Procdurs. Cary: SAS Institut Inc., Cntrs for Disas Control and Prvntion (CDC). Continuous NHANES wb tutorial, ag standardization and population counts. NHANES/NHANESAnalyss/agstandardization/ag_ standardization_intro.htm (2013, accssd 20 April 2014). 30. Currnt Population Survy (CPS), gov/cps/ (2013, accssd 1 March 2013). 31. Klin R and Schonborn C. Ag adjustmnt using th 2000 projctd U.S. population. Halthy Popl

14 60 Chronic Rspiratory Disas 12(1) Statistical Nots, no. 20. Hyattsvill: National Cntr for Halth Statistics, Li CY and Sung FC. A rviw of th halthy workr ffct in occupational pidmiology. Occup Md (Lond) 1999; 49(4): Bcklak MR and Whit N. Sourcs of variation in spiromtric masurmnts. Idntifying th signal and daling with nois. Occ Md (Philadlphia, Pa) 1993; 8(2): Kauffmann F, Drout D, Lllouch J, t al. Occupational xposur and 12-yar spiromtric changs among Paris ara workrs. Br J Ind Md 1982; 39(3): Sunyr J, Zock JP, Kromhout H, t al. Lung function dclin, chronic bronchitis, and occupational xposurs in young adults. Am J Rspir Crit Car Md 2005; 172(9): LVan TD, Koh WP, L HP, t al. Vapor, dust, and smok xposur in rlation to adult-onst asthma and chronic rspiratory symptoms: th Singapor Chins Halth Study. Am J Epidmiol 2006; 163(12): Zock JP, Sunyr J, Kogvinas M, t al. Occupation, chronic bronchitis, and lung function in young adults. An intrnational study. Am J Rspir Crit Car Md 2001; 163(7): Darby AC, Watrhous JC, Stvns V, t al. Chronic obstructiv pulmonary disas among rsidnts of an historically industrialisd ara. Thorax 2012; 67(10): Holm M, Kim JL, Lillinbrg L, t al. Incidnc and prvalnc of chronic bronchitis: impact of smoking and wlding. Th RHINE study. Int J Tubrc Lung Dis 2012; 16(4): Korn RJ, Dockry DW, Spizr FE, t al. Occupational xposurs and chronic rspiratory symptoms. A population-basd study. Am Rv Rspir Dis 1987; 136(2): Mhta AJ, Midingr D, Kidl D, t al. Occupational xposur to dusts, gass, and fums and incidnc of chronic obstructiv pulmonary disas in th Swiss Cohort Study on Air Pollution and Lung and Hart Disass in Adults. Am J Rspir Crit Car Md 2012; 185(12): Hnizdo E, Sullivan PA, Bang KM, t al. Airflow obstruction attributabl to work in industry and occupation among U.S. rac/thnic groups: a study of NHANES III data. Am J Ind Md 2004; 46(2): Johnsn HL, Kongrud J, Htland SM, t al. Dcrasd lung function among mploys at Norwgian smltrs. Am J Ind Md 2008; 51(4): Cockcroft A, Sal RM, Wagnr JC, t al. Post-mortm study of mphysma in coalworkrs and non-coalworkrs. Lanct 1982; 2(8298): Kumpl ED, Whlr MW, Smith RJ, t al. Contributions of dust xposur and cigartt smoking to mphysma svrity in coal minrs in th Unitd Stats. Am J Rspir Crit Car Md 2009; 180(3): Ligh J, Driscoll TR, Col BD, t al. Quantitativ rlation btwn mphysma and lung minral contnt in coalworkrs. Occup Environ Md 1994; 51(6): Naidoo RN, Robins TG and Murray J. Rspiratory outcoms among South African coal minrs at autopsy. Am J Ind Md 2005; 48(3): Ruckly VA, Gauld SJ, Chapman JS, t al. Emphysma and dust xposur in a group of coal workrs. Am Rv Rspir Dis 1984; 129(4): Bcklak M, Irwig L, Kilkowski D, t al. Th prdictors of mphysma in South African gold minrs. Am Rv Rspir Dis 1987; 135(6): Barraclough R, Dvrux G, Hndrick DJ, t al. Apparnt but not ral incras in asthma prvalnc during th 1990s. Eur Rspir J 2002; 20(4): Edr W, Eg MJ and von Mutius E. Th asthma pidmic. N Engl J Md 2006; 355(21): Masoli M, Fabian D, Holt S and Basly R. Global Initiativ for Asthma Program. Th global burdn of asthma: xcutiv summary of th GINA Dissmination Committ rport. Allrgy 2004; 59(5): Buthr DA and Suthrland ER. Ovrwight, obsity, and incidnt asthma: a mta-analysis of prospctiv pidmiologic studis. Am J Rspir Crit Car Md 2007; 175(7): Camargo CA Jr, Wiss ST, Zhang S, t al. Prospctiv study of body mass indx, wight chang, and risk of adult-onst asthma in womn. Arch Intrn Md 1999; 159(21): Ludr E, Ehrlich RI, Lou WY, t al. Body mass indx and th risk of asthma in adults. Rspir Md 2004; 98(1): Bakk P, Eid GE, Hanoa R, t al. Occupational dust or gas xposur and prvalncs of rspiratory symptoms and asthma in a gnral population. Eur Rspir J 1991; 4(3): Eagan TM, Gulsvik A, Eid GE, t al. Occupational airborn xposur and th incidnc of rspiratory symptoms and asthma. Am J Rspir Crit Car Md 2002; 166(7): Zilinski J, Bdnark M, Gorcka D, t al. Incrasing COPD awarnss. Eur Rspir J 2006; 27(4):