Howard (19701, Bates (1973), Sharp et al. (19731, Fletcher et al. (19761, Fletcher and Peto (1977), Bosse et al. (19811, Beck et al. (19821, and Clement and van de Woestijne (1982). Although these investigations did not characterize the course of airflow obstruction across the entire human lifespan, the results provide a conceptual model for considering its development (Figure 15). Ventilator-y function, gener- ally measured by the FEV1, increases during childhood and reaches a maximum level during early adulthood (Cotes 1979; Knudson et al. 1983). From this peak; the FEVl gradually and progressively declines with age. In people who develop airflow obstruction, a similar gradual loss of function occurs, but at a more rapid rate (Fletcher et al. 1976; Speizer and Tager 1979). Continued excessive loss of FEVl eventually results in symptomatic airflow obstruction when ventila- tory function reaches a level at which activities are limited and dyspnea occurs. Evaluation by a physician for symptoms may lead to a clinical diagnosis at this point in the natural history of the disease process. This model may not satisfactorily describe the development of airflow obstruction in all individuals (Burrows 19811, but the accumulating evidence, reviewed below, indicates that a sustained excessive loss of ventilatory function most often leads to the development of clinically important chronic airflow obstruction. In the conceptual model (Figure 151, there are three different measures of the frequency of airflow obstruction in a particular population: the prevalence of reduced ventilatory function as measured by the FEV1, the FEVJFVC ratio, or other physiological parameters; the prevalence of physician-diagnosed airflow obstruc- tion; and the frequency of excessive functional loss in a population followed over time. The first two measures can be determined from a single cross-sectional survey, whereas the third requires longitudinal observation. At present, scant data are available for the third category. The prevalence of physician-confirmed airflow obstruction is determined not only by the proportion of affected people in the population, but also by the patterns of medical care access and usage and the diagnostic practices of individual physicians. Furthermore, the clinical labels applied by physicians to people with airflow obstruction are variable and may include "chronic bronchitis," "emphysema, " "COLD," and other terms. Thus, estimates of disease prevalence based on reported physician diagnoses may differ from those derived from physiological assessment. Prevalence of Airflow Obstruction Numerous populations throughout the world have been surveyed to assess the prevalence of airflow obstruction (Stuart-Harris 1968a, 1968b; Higgins 1974). Most often, the investigative techniques have included a respiratory symptoms questionnaire and measurement of pulmonary function, generally with a spirometer or peak flow meter. 76 4 3 zi 5 Z= $ 2 ( 1 1 I I 1 I I 25 35 45 55 65 75 FIGURE 15.-Decline of FEVl at normal rate (solid line) and at an accelerated rate (dashed line) NOTE. A: person who haa attained a "normal" manma FEV, during lung growth and development. B. person whose maximal FEVa has been reduced by childhood respirator? infectmn SOURCE: Ssmet et al. 11983, The latter technique has the disadvantage of effort dependence. Early recognition of the potential problem of observer bias led to the development of standardized methods (Cochrane et al. 1951; Higgins 1974; Ferris 1978). Thus, most investigators throughout the world have used the British Medical Research Council questionnaire in the original form or with some modifications (Samet 19781. Standardiza- tion has been less uniform for lung function measurements, but minor variations in procedures would not introduce important differences in disease prevalence among the various populations examined. Although many different populations have been surveyed since the 195Os, surprisingly few published reports provide data concern ing the prevalence of airflow obstruction in the general population cT:Ables 4 and 5). Comparisons among the available studies are limited by varying methodologies and inconsistent approaches in calculating rates. For example, only crude rates are available in some reports, and reference populations for age standardization also vary. The investigations summarized in Tables 4 and 5 were selected because t,hey offer estimates of the prevalence of airflow obstruction in defined community-based samples. Those reports that describe mean levels of lung function parameters but not their distributions were excluded. Investigations of specific occupational groups were also excluded because prevalence estimates based on such popula- tions may be biased by the overrepresentation of healthy persons (Monson 1980) and workplace exposures may have affected the frequency of disease. For the United States, the available information spans the time period 1961 to 1979 and covers most geographic regions (Table 4). Regardless of the definition, it is apparent that airflow obstruction is common among adults in the United States. A higher proportion of men than women is affected, and the prevalence increases with age (Ferris and Anderson 1962; USPHS 1973; Lebowitz et al. 1975; Detels et al. 1979; Samet et al. 1982). Few minority populations have been studied. In New Mexico, Hispanic whites had a lower prevalence of physician-diagnosed current chronic bronchitis or emphysema than non-Hispanic whites Garnet et al. 1982). Although blacks have been included in several surveys (Bouhuys et al. 19791, prevalence e&mates for this racial group have not been published. The available data (Table 4) do not permit a satisfactory assessment of changes in prevalence rates with time over the years 1961 to 1979. The National Health and Nutrition Examination Surveys iNHANES 1) included spirometry in their evaluation of a represen- tative sample of the U.S. population. The numerical values for these measures are reported by age, sex, and smoking status for the white population in the tables in the appendix to this chapter. The changes in mean values of these measures between age groups are also presented for white male and female smokers and nonsmokers in Figures 16 through 23. Differences between smokers and nonsmok- ers are evident for each of these spirometric measures. These differences are portrayed for successive age groups at one point in time, and therefore cannot be used to describe the changes with age or smoking status that one would expect in an individual or yJpdat.ion followed sequentially. These data represent only those people in the study populat.ion who were willing and physically able to mnximaliy exert themselves on the various spirometry tests;. Others were discju11ified by the examining physician because of eslstirig rn~~l~c:il f, ' aonditions. The sampling nonresponse was higher anon:: ::.epments of i;;c~ population expected to perform less well on the test i:icludi:l:: Y' ;,ie with existing airflow limitation. Therefore, TABLE 4.-Prevalence of indices of airflow obstruction in selected U.S. adult populations Author, year of study. Number and typz location, reference of population Index Prevalence (per loo) Higgins and Kjelsbeq, 1969-1960, Tecumaeh, Michigan u967) 4,500 men and women. 20 years or older, community sample Emphysema bawd on physician history and examination Me" Women 4.1 ' 1.1 ' Higgins, 19621979, Tecumaeh, Michigan (15183 4.916, 4,443, and 4,933 men and women, 16 to 74 yema old, in 1962&s, 1967-69,1978-79 Otmtrwtive airways disease: FEV, leea than 65% predicted, and FEV,/FVC ratio less than 80%: I!&&65 196769 19x5 79 Men 481 372 :I 7 2 Women 25t 142 22' Ferris and Anderson. 1961. Berlin, New Hampshire (19fa 1,167 men and women, community sample Irreversible obstructive lung disease, including wheezing, dyspnen, or FEV,/FVC ratio less than 60% Men Women R.6l 8.1 ' Mueller et al., 1967, Glen- wocd Springs, Colorado (1971) IT.!3 Public Health Service, 1970, united states (1973) 609 men and women, community aample 116,000 men and women, nationwide awnpie Uwonic airway obstruction: FF.V,/FVC ratio less than 60% Preaen~+z of the condition during the previous year Me" 1321 Women 1.5' --__-- - Chronic bronchitis Men 3.1 ' Women 3.4 ' Emphysema Men 1.0 I Women 0.3 ' E! TABLE 4.-Continued Author, year of study, Number and type location, reference of population Index Prevalence (per 100) L&wit2 et al., 1972-1973, Tucson, Arizona (1975) 3,605 men and women. adukaandchildren. community sample Physiciarwonfn-med illness. current Men over 44 yeam Chronic bmncbitia 10.2 Emphysema 13.3 ' Women over 44 years Chronic bmncbitia 9.0 ' Emphysema 4.3 ' Knudson et al., 19721973. Tucson, Arizona (1976) 3,605 men and women, adulta and children. community sample FEV, and FEV,/FVC ratio lower than 95th percentile for "normal" Asymptomatic cigarette smokera m, 7.6 ' FEVJFVC 8.1 ' Detela et al., 1973-1974, Burbank and Lancaster, cdifornia (1979) 3,465 and 4,509 men and women, in Burbank and Lancaeter. respectively, community luUnpleJ3 FFX, leaa than Em7 of predicted value Lancaster 18-59 yla 0.8' fioyrs 6.5 a Bul&lk 18-59 yra 1.0' 6ovrs 6.2' Tager et al., 19751974, East J3oe.h. Mamachuaetts (197M 1,770 men and women, wmmunity sample of index subjecta and their relatives FEV, less than 65% of predicted Men Women 5.6 ' 3.4 ' Fen-in et al., 19761977, six cities in the U.S. (1979) 7.909 men and women. community sample FEY,/Fvc leas than, eaxlal tDti% Men Women 5.0 ' 1.9' TABLE I.--Continued Author, year of study, Number and type location, reference of population Index Prevalence (per 100) Samet et al., 1976-1979, Albuquerque, New Mexico u982) 1,722 men and women, canmunity sample Phyxiciandiagnoeed current chmnic bronchitis or emphysema Non-Hipanic whites Men 3.6' Women 3.4' Hispanic wbitea Men 0.8' Women 1.6' ' Crude rate. `Age-adjlwted rate. * Age and eewadjueted rate. TABLE &-Prevalence of indices of airflow obstruction in selected adult non-U.!% populations Author, year of study, Number and type location, reference of population Index Prevalence (per 100) Anderson et al., 1963. 558 men and women, Obstructive lung disease, Men 12.6' Chilliwack, British community sample including wheezing, dyspnea, `Women 87' Columbia (19653 or FEV,/FVC ratio less than 60% FEV,/FVC ratio less than Men 7.3 ' 60% Women 3.5 ' Mimica, 1969, Croatia, 4,214 men and women. FEV,/FVC ratio less than Men 8.3 ' Yugoslavia (197Ti samples of six 60% Women 1.9' oommunitiee Sawicki. 1968, Krakow, 4,355 men and women, FEV,/FVC ratio less than Men 7.0' Poland (2977) community sample 60% Women 5.0 ' Huhti et al.. 19681970, 1.162 men, community FEV,/FVC ratio less than Men 7.6 ' Hankaeahni. Finland (1978 l%SIlIple 60% Brown and Gajdusek, year 240 men and women, Chronic obstructive airway Men and not stated. Weatern community sample disease: clinical and spim women 7.9 ' Camline Islands (1978) metric criteria Anderson, year not stated, 770 men and women, FEV,/FVC ratio leas than Men 9.0 ' Lufa, Papua New Guinea 25 yeam or older, 60% Women 3.6 ' (1979) community sample ' Crude rate the estimated means are probably overestimate> of the true popula- tion values. Nevertheless, the figures clearly portray the magnitude of the effect that smoking exerts on expiratorv flow rates in a national population sample. Airflow obstruction is also prevalent outside t.he United States (Table 5). The disease can be identified in both technologically advanced and less developed populations. As in the United States, in other countries the prevalence of airflow oba. 3667 . - Never smokers - - - Current agarette smokers ~_--- .~~~-~~.-~T--- - 25-34 35-44 45-54 Age group .---r..~---.-~--~ 5M4 65-74 3712 -===\y,-.L- 26*3 `. . `. ----._---. 2712 2533 o- i -_.. i.-~-.~ 25-34 3544 4554 Age group 55-64 65-74 FIGURE 23.-Mean forced vital capacity for white persons by smoking status, sex, and age, United States, 1971-1975 NOTE Values udjusti by the direct method to reflect the age distribution of the US populatlan at the midpoint of the survey. SOURCE Kational Center for Health Sttltlstics Unpubhshed data from the first Natuxaal Health Nutrition and Fxamlnstion Surwy fNHANEX lr 91 `CAtiLK 6..--Pusbulat~:d risk factors for airflow obstruction during childhood _" _.~ -.... -.- . ..-_ -I-.-- Actwe clgaret& smokmg :&ir pollubiun. indoor and outdoor Airnajs hypeneartivity A~WY - . . .._- .-LX.. - . I_-.-- -----be-. -......- _ I-~II-. .-__ _.-. ..- .-_. _ .--.. , `3 .& .lSlED iit;+. F.~c'!I;~G FOR AIHF'LOW OFSTRLKTION DL'RIh'G ADULTHOOD _-I- -.---.---m-w-^--. __I_ Actlre cqawtte smoking Alpha,-antltrjpsin deficient) _~_ _._ _.. .----__----- _____- PI'TA iIVE ~1% P.1: IXXS FOR AIHFLGW OBSTRUC'I'ION DURING ADULTHOOD ABH secretor status Air pollution Airways hyperreactivity Alcohol consumption A~PY Childhood respiratory illnesses Familial factors Occupation Passive exposure to t&acco smoke Respiratory illnesses Scciwconomic status occupational groups (Table 10) with exposures that have little or no effect on lung function. The selected studies are all cross sectional in design and thus describe the relationship between cigarette smoking and lung function level at only a single point in time. Investigations in the United States, spanning the time period 1958 to 1977, convincingly demonstrate that cigarette smoking is a strong determinant of FEVl level and the prevalence of airflow obstruction (Table 8). In every population for which prevalence data are available, airflow obstruction is more common among smokers than among nonsmokers (Mueller et al. 1971; Knudson et al. 1976; Detels et al. 1979; Rokaw et al. 1980). In fact, in a multivariate analysis of determinants of airflow obstruction in East Boston, lifetime cigarette consumption was the only statistically significant predictor (Tager et al. 1978). Data from populations outside the United States (Table 9) and from a variety of occupational groups (Table 10) confirm the importance of cigarette smoking. Effects of cigarette smoking on FEVi level have been readily demonstrated in employed populations 92 TABLE &-Association between cigarette smoking and FEV, level in selected U.S. adult populations Author, year of study, Number and type location, reference of population Findings Ashley et al.. 1956. Framingham, Massachusetts, (1975) 1,236 men and women, 37 to 89 years of age By linear regression, significant decline of FEX,/FVC ratio with pack-years of cigarette consumption in men; similar decline demonstrated in women, but not significant for all ab!e mute Higgine and Kjelsberg 19% 1980, Tecumeeh, Mich!gan (1967) - Higgins et al., 1963, Marion County. West Virginia 1196all I_..------ Higgins et al., 1962-1965, l'rcumwh. lIichiian (1977) 5,140 men and women, 16 to 79 yeare of age 926 white men, 20 to 69 years of age 4,669 men and women, 20 to 14 years of age - Age-adjusted mean FEV, Oiters) Men Women Nonsmokers 3.32 2.34 Ex-smokera 3.31 2.34 Current smokers 3.12 2.26 Mean FEV, (liters) Nonsmokers 3.64 Ex+mokers 3.25 Current smokers 1-14/day 3.67 15-2.4lday 3.51 > mday 3.30 Mean normalized FEV, score Men Women Nonsmokers 10.2 10 1 Ex-emokers 9.9 10.0 Current smokers c2O/day 9.8 9.9 2 2oMay 9.5 9.6 -~.__l___-.__l~---- Prevalence of E'E:V : i FVC <: Go% Men Women Mlwl'r" ct n'. 1`W 1 . Glenwood, cid!LI f%)(l :xn and women. Nonsmokers 3 ; %;! to 69 JY'Ul-8 or age Current smokers 19 2 (2971) .- ~.-- Fen% et al., 1967, &rlin, 848 men and women, By multiple r-ion, in men and women, FEV, drops by New Iiampehire (197.3 3OtcW)yearsofage 0.01 liters for each cigarette smoked per day -.-._-- -. _-- _ _----- -~ ___--. .-.---__ Burrowe et al., 1972.-1!?7?. 2369 men and women, By multiple regression analysis, FEV, drops by 0.31 and Tucson, Arizona iI above 14 years of age 0.24 percent of predicted value per pack-year of smoking in men and women, respectively .____ --- ---..---- _- Knudson et al., 19X1973. 2,7.35 men and women, Pravalence (%) of abnormal FEV, and/or FIW,/FVC Tucson, Atiana (f97fJ all ages Asymptomatic nonsmokers 8.3 Asymptomatic smokers 13.3 __-- ---. --.~ Tsger and S+vr, 1973.397!. 633 men and women, By multiple regression, in men and women, significant FM Ftiton. Massachusett 15t years of age reduction of an FJXV, score with increasing lifetime /19707 consumption, and in smokers compared with nonsmokers Tagger et al., 197:%1974. East Boston, Msssarhwe!k !!9,3 1,251 men and woman, By multiple logistic analysis, lifetime cigarette consumption only significant pradictor of airflow obstruction, defmed as FEV, laea than 65% predicted 4.6W men and women, 7t yearsofage By multiple regression analysis, significant dose-response relationships of adjusted residual FJIV, with measurea of cigarette smoking: duration, pack-years. and cigarettes per day TABLE %-Continued Author, year of study, Number and type location, reference of population Findings Ferris et al., 1974-1977, U.S. communities (19791 Detele et al., Rokaw et al., 1973-1975, Burbank, Lan- mater, Long Beech, California (lhtels et al.. 1979, Rokaw et al., 1960) 8,480 men and women, 25to74yeareofage Approximately 8,000 men and women, 18 yeare or older Mean r&dual FEV, (liters) after correction for height and age Lifetime packs Men Women None 0.25 0.06 <3.ooo 0.21 0.04 3.~999 0.01 -0.05 9,ooo-17,999 -0.19 -0.20 2 l&o00 -0.45 -0.28 F'revalence (%Y of FEV, below 75% predicted, age and eex-adjusted Never smoked Current smoker 1859 years old Burbank 6.6 12.5 Lancaster 3.4 6.6 Long Bench 5.3 10.0 260 years old Burbank 15.9 23.5 Lancaster 13.4 21.7 TABLE 9.-Association between cigarette smoking and lung function in sele&ed non-U.S. populations Author, year of study, Number and type location, reference of population Findings Hi, 1956, VaIe of GlamorgaIl, wales mm 661 men and women, 25 to 74 yearn of age lr men, reduced peak tlow rates and indirect maximum v&ntary ventilation in smokers compared with nonsmokers; no effect of smoking in women Higgins et al., 1957 Stavely, England (1959l 776 men, aged 25 to 34and55to64 Mean indirect maximal breath capacity (liters) 25ta34yrE 55ta64yl-n Nonsmokers 145 101 Exsmokers 143 89 Current smokers Light 140 87 HWVY 133 80 H&inn et al., 1966, Rhondda 537 men, aged 36 to 64, Mean indimct maximal breathinx canacit~ titers). men Fa& -. - Walea (1961) and 173 women, aged55to64 Miners Nonminers Nonamokern 93.1 114.6 Ex+mokern 93.6 106.9 Current smokers Light 89.0 104.1 HeavY 88.3 99.4 No effect of smoking in women TABLE 9.-Continued Author, year of study, Number and type location, reference of population Findings College of General Practitioners, 787 men and 762 Age-adjusted mean PEFB' flitera/minute) 1966, Britain (1961) women, aged 40 to 64 Men Women Nonsmokers 448 316 Ex-nmokern 417 300 Current smokers 1-lllday 412 314 15-24/day 399 310 > 25lday 398 265 SluisCremer and Sichel, 533 men, 36 yearn Reduced FEV, and PEFR' with increased tobacco mnsumption 1962-1963, Carletonville, or older South Africa (1Si!7~ Huhti, 1961. Harjavalta, 420 men, 608 women, All women, nonsmokers; in men, reduced FEV, and PEFB ' in Finland (1967~ aged4ot.oe4 smokers mmpared with nonsmokers Wilhelmsen et al., 1963. 339 men. aged 50 Gi5teborg, Sweden (1969) Mean FEV, (liters) Nonsmokers 3.72 &-smokers 3.71 Current smokers 1-14 g/day 3.58 > 15 g/day 3.36 Huhti et al., 1968-1970, 1,162 men, aged 25 to Reduced FEV, in smokera compared with nonsmokers; increased Hankaaalmi. Finland (1978) 69 prevalence of FEV,/FVC ratio lese than 60% in smokers TABLE 9.-Continued Author, year of study. Iwatinn. reference Number and type of population Findings MimIca, 1969. Croatia, 4,214 men and women, Yugoslavia (1979 35 to 54 years of age Nonsmokers Ex+mokers Current smokers Light H-V Mean FEV, (liters) Men 3.56 3.57 3.42 3.42 Women 2.62 2.70 2.64 2.66 Neri et al, 19691973. Sudbury and Ottawa. Canada 11975 Manfreda et al, 1974, Portage la Prairie and Charleswoo& Canada (197x) --- -- Andemon. year not stated, Karkar Island. Papua New Gtinm 11976-I Anderson, year not stated, Lufa, Papua New Guinea (2979) 5,466 men and women, 14 years of age or older 502 men and women, 25toXiyearsofage 548 men and women, 25 years of age or older 733 men and women 25yearsofageor older Declining ratio of FEV!/FVC with number of cigarettes smoked MY Significant regression of FFV,/FVC ratio on number of cigarettes smoked daily Age and heightadjusted mean FEV, (liters) Men Women Nonsmokers 2.56 2.13 Smokers 2.40 2.01 Age and heighta&sted mean FEV, (liters) Men Women Nonsmoker 2.58 2.36 Exsmoker 2.62 2.27 Occasional 2.57 2.29 R@idw 2.63 243 TABLE IO.-Association between cigarette smoking and lung function level in selected occupational groups Author, year of study, Number and type location, reference of population Findings Sharp et al., 1960-1961, 1.667 men, aged 43 to Chicago, U.S. (1965) 56 years. employed at an electronics plant ..-_ --~___ Fletcher et al., 1961. 1,136 men aged 30 London, England (2976) to 59, employed at bank or in maintenance of transportation equipment f, --__ i- -- Goldsmith et al. 1961 San Francisco. U.S. ima' 3,311 longshoremen Mean FEV, (liters) Nonsmokers Smokers 40 cigarettes/day 3.15 3.02 2.90 3.28 3.16 2.81 3.05 2.99 2.94 100 97 93 93 94 E TABLE IO.-Continued Author. year of study, Number and type location, reference of population Rndinga Bidchum et al.. 1961, La 1,456 men employed in Prevalence (per 100) of FTV,/FVC ratio less than 70 percent Angeles, U.S. (I96ZI various induetrien Nonsmokers 1.6 Smokers 18.8 Coata et al.. 1962. Detroit, 1,584 male and female Reduced FFX, and FFX,/F'VC ratio in smokers of 25 or more U.S. (1965) pcwtal employees, cigarettes daily compared with nonsmokers aged 40 or older Deneen et al., 1961-1983, New York City, US. (2969) 12,500 males employed 88 postal or transit workers Age- end heightadjusted FJW, W..ere) Pcetal workers Transit workers Band6 et al., 1980-1975. Belgium (1980) 7.123 male military personnel, * few over age 45 white Nonwhite White Nonwhite Nonsmokers 3.29 3.05 3.39 3.08 Cigarette smokers <25gperday 3.14 2.95 3.15 3.00 2% B per &Y 3.06 2.93 3.02 2.95 By multiple regression, in crcesaxtional analyeie, signiiiwnt effect of smoking on FEV, level after age 35 Cornstock et al.. 1962-1963 and 1967. U.S. and Japan (19731 Three cme+eectional Mean FJW, level as percent predicted studies of men working U.S. Jaw for telephone company; Study 1 Study 2 U.S.-l,302 and Cigarettea per day 1,194 subjects, aged None 106 103 99 40 to 65. 6% in 1-14 104 101 100 study; Japan--592 15-24 98 92 98 subjecta, aged 40 to 60 2% 95 93 99