CHRONIC OBSTRUCTIVE PULMONARY DISEASE IN BLAC AND WHITES: PULMONARY FUNCTION NORMS AND RISK FACTORS Richard F. Gillum, MD Hyattsville, Maryland
Chronic obstructive pulmonary disease (COPD) and asthma are significant causes of illness and death in blacks. Racial differences in normal values of pulmonary function tests must be considered in both patient care and research. Assessment of risk factors is an important part of COPD management and prevention. An extensive review of data from the National Center for Health Statistics and from other population-based studies confirmed lower lung volumes in blacks compared to whites. However, the ratio of forced expiratory volume in 1 second to forced vital capacity was not lower in blacks; racial differences in flow rates were inconsistently reported. Thoracic dimensions were smaller in blacks than in whites in healthy populations. The cause and the physiologic and pathophysiologic significance of these racial differences are unknown. Population-based studies in blacks have firmly established only age and cigarette smoking as risk factors for COPD other than asthma. In 1987, 43% of black men aged 45 and older smoked cigarettes compared to only 30% of white men. Further research is needed on racial From the Office of Analysis and Epidemiology, National Center for Health Statistics, Hyattsville, Maryland. Requests for reprints should be addressed to Dr Richard F. Gillum, Office of Analysis and Epidemiology, National Center for Health Statistics, Presidential Bldg, Rm 1000, 6725 Belerest Road, 3700 East West Hwy, Hyattsville, MD 20782. JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 83, NO. 5
differences in pulmonary function and the effects of multiple risk factors to enhance understanding of COPD etiology and prevention. More vigorous smoking prevention and cessation efforts should be targeted for blacks by physicians and public health organizations. (J Nati Med Assoc. 1991;83:393-401.) Key words * spirometry * Lung volume measurements * Smoking
Chronic obstructive pulmonary disease (COPD) and asthma are significant causes of morbidity and mortality in blacks." 2 Pulmonary function testing is essential in managing and investigating these conditions, and assessing risk factors is essential in managing, preventing, and investigating COPD. Smoking prevention or cessation is all the more urgent in individuals with abnormal pulmonary function, COPD symptoms, or nonmodifiable risk factors for COPD. Many published studies have reported lower lung volumes in blacks compared to whites at all ages."2 These racial differences and their relationship to racial differences in COPD have been inadequately studied. A further unresolved question is whether racial differences in known or suspected risk factors in COPD can explain racial differences in disease occurrence. This article examines racial differences in pulmonary function and risk factors for COPD in blacks that may explain racial differences in COPD using national data from the National Center for Health Statistics (NCHS) 393
CHRONIC OBSTRUCTIVE PULMONARY DISEASE
Milliliters 6000_
6000iliters
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. ...
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*vs
White men Black men White women
Black women
40003000
Milliliters 5000
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.
4000
3000
.
...
White men Black men White women Black women
..........
f
*..~~~~~~~I 3000.
2000
..
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01~
0 30
40
50
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70
Age
Figure 1. Mean forced vital capacity (FVC) of black and white adults who never smoked ages 25 to 74 years, reproducible best trial only, by sex and age: United States, 1971.75.6 Note: Mean for black men ages 35 to 44 has a standard error greater than 15% and should be interpreted with caution.
and other previously published reports, with emphasis given to population-based studies.3
PULMONARY FUNCTION Estimates of spirometric function for US adults were obtained in the first National Health and Nutrition Examination Survey (NHANES 1).4-6 However, satisfactory data were obtained in only 25% to 67% of blacks in the sample, with the lowest rates occurring in black women aged 55 to 74 years.6 Satisfactory data were obtained in 48% to 88% of whites. Forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) were lower in blacks than in whites in NHANES I both in smokers and in nonsmokers in almost all age and sex groups (Figures 1 and 2). There were no consistent racial differences in FEV,/FVC.6 The highly effort-dependent measures, peak flow rate and maximal expiratory flow rate were consistently lower in blacks than in whites in smokers and nonsmokers in every age and sex group. However, flow rates were not adjusted for initial volumes. Differences were much less for the effort-independent forced expiratory flow rate at 75% of forced vital capacity, suggesting racial differences in participants' efforts in response to the NHANES I protocol. These NHANES I data were based on results from reproducible best trials for which overall response rates and numbers of participants in age strata were low for blacks. The data must be viewed with caution because 394
.....
30
40
50
60
70
Age
Figure 2. Mean forced expiratory volume at I second (FEV1) of black and white adults who never smoked ages 25 to 74 years, reproducible best trial only, by sex and age: United States, 1971-75.6 Note: Means for black men ages 35 to 44 and 45 to 54 have standard errors greater than 25% and should be interpreted with caution.
of potential bias, similar to most other published spirometric data. The effects of controlling height, weight, body mass index, education, income, region, and other variables on racial differences have not yet been published for NHANES I. Although no thorough analysis has been published on NHANES I data, examination of published tables indicates that unadjusted differences between smokers and nonsmokers in mean FEV1 were consistently greater for whites than for blacks and the decline in mean FEV1 with age in smokers was greater for whites than blacks whether expressed as mL/year or as percent of FEVy for ages 25 to 34 years.6 The NCHS also has published spirometric data for children aged 6 to 11 years who were surveyed from 1963 to 1965.7 In the Health Examination Survey Cycle II (HES II), black boys aged 6 to 11 had lower FVC than white boys the same ages. Differences were greatest at 9 to 11 years. Black girls had consistently lower FVC than white girls. Sex differences were less consistent in blacks than whites. The average black-white difference was about 10% to 15%. The average difference was 236 mL for boys, 186 mL for girls, and 226 mL for both sexes. Black-white differences were most consistent when examined by height rather than age, curves being more nearly parallel for each group.7 However, when sitting height was used, the racial difference was decreased by approximately half. This presumably JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 83, NO. 5
CHRONIC OBSTRUCTIVE PULMONARY DISEASE
TABLE 1. MEAN (SE) LUNG FIELD AREAS* FROM POSTERIOR-ANTERIOR (PA) AND LATERAL CHEST X-RAYS IN A NATIONAL SAMPLE OF WHITES AND BLACKS PA Lateral Age White Black White Black Men 25 to 34 479.22 443.31 405.24 386.95 4.34 8.93 3.22 6.88 35 to 44 472.59 422.27 416.28 374.81 4.69 15.56 3.54 10.44 45 to 54 464.94 439.44 431.18 384.09 4.27 7.56 3.36 8.17 55 to 64 467.23 447.63 451.79 410.94 4.20 10.41 3.81 9.29 65 to 74 461.89 463.59 455.80 397.39 3.84 7.38 3.83 8.50 Women 25 to 34 409.90 366.71 318.27 296.23 2.94 6.08 3.08 3.67 35 to 44 418.18 364.84 336.55 306.56 2.69 6.97 2.20 5.68 45 to 54 408.72 357.17 349.57 322.18 3.13 5.66 2.25 7.06 55 to 64 379.15 339.50 356.41 324.96 3.06 7.21 2.50 7.13 65 to 74 362.74 332.83 359.67 336.02 3.11 7.11 2.97 6.50
*From planimetry,
Cm2.
relates to the lower sitting heights in blacks compared to whites and to the relationship of lung volume to the size and shape of the thorax. However, in individual children, sitting height was not more highly correlated with FVC than with standing height.7 Limitations of these data discussed elsewhere include the exclusion of 1129 of 6932 (16%) spirograms as technically unsatisfactory, differential exclusion rates by race, and unavailability of FEV1 and maximal mid-expiratory flow rate due to technical difficulties.7'8 However, racial differences in FVC were probably estimated fairly accurately. Unfortunately, spirometry data were not available from HES Cycle III in 12 to 17 year olds.7-9 When analyzed and published, data from NHANES II will provide spirometry data for 6 to 24 year olds examined between 1976 and 1980. 10 In NHANES I, internal chest measurements from x-rays of a subsample of adults and a number of anthropometric measurements were available that might have shed light on racial lung volume differences from this national sample.4"'1 Tables 1 and 2 show mean lung field areas by planimetry'2 for 5608 whites and 840 blacks, and thoracic diameters in 2937 whites and 575 blacks by race, age, and sex. In these weighted analyses, blacks in the sample had smaller lung field JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 83, NO. 5
areas and thoracic diameters than whites. Greater racial differences in diameters were obtained in a comparison of European and African miners due to the small overall size of the Africans.13 Total lung capacity (TLC), residual volume (RV), and RV/TLC calculated from NHANES I x-ray data have been published previously.'4 Blacks had a lower mean TLC than whites in all age and sex subgroups. Consistent racial differences were not observed for RV or RV/TLC. Prediction equations were presented for blacks and whites. As in children, the ratio of sitting to standing height was lower in black adults than in white adults.7"15'18 Sitting heights were consistently lower in blacks than in whites with little difference in standing height. In NHANES I, chest circumference at full expiration was not consistently different in black men compared to white men but was greater in black women than in white women, perhaps due to greater obesity in black women. At full inspiration, chest circumference was slightly smaller in black men than in white men but remained greater in black women than in white women. Available data suggest that at least some of the black-white difference in lung volume in adults is associated with a similar difference in thoracic capacity. Numerous other published reports spanning more 395
CHRONIC OBSTRUCTIVE PULMONARY DISEASE
TABLE 2. MEAN (SE) THORACIC DIAMETERS* FROM POSTERIOR-ANTERIOR AND LATERAL CHEST X-RAYS IN A NATIONAL SAMPLE OF WHITES AND BLACKS Lateral 2* Lateral It Transverse White Black Black White White Black Age Men 17.96 30.55 18.75 17.97 18.81 25 to 34 31.52 0.71 0.16 0.38 0.34 0.15 0.16 31.27 19.25 17.90 19.37 17.95 31.67 35 to 44 0.46 0.16 0.45 0.16 0.48 0.16 30.05 19.67 18.10 19.81 18.10 31.66 45 to 54 0.38 0.13 0.34 0.15 0.39 0.15 18.50 31.72 20.21 18.55 20.31 30.54 55 to 64 0.17 0.17 0.33 0.14 0.37 0.32 31.21 30.67 20.02 17.54 20.07 17.55 . 65 to 74 0.43 0.37 0.17 0.41 0.16 0.11 Women 14.87 27.20 26.56 15.21 14.82 15.10 25 to 34 0.11 0.27 0.12 0.30 0.28 0.15 15.35 27.65 27.00 15.89 15.41 15.79 35 to 44 0.12 0.39 0.36 0.13 0.38 0.12 27.08 16.54 16.49 16.46 16.40 27.29 45 to 54
Chronic obstructive pulmonary disease (COPD) and asthma are significant causes of illness and death in blacks. Racial differences in normal values of pulmonary function tests must be considered in both patient care and research. Assessment of risk factors is an important part of COPD management and prevention. An extensive review of data from the National Center for Health Statistics and from other population-based studies confirmed lower lung volumes in blacks compared to whites. However, the ratio of forced expiratory volume in 1 second to forced vital capacity was not lower in blacks; racial differences in flow rates were inconsistently reported. Thoracic dimensions were smaller in blacks than in whites in healthy populations. The cause and the physiologic and pathophysiologic significance of these racial differences are unknown. Population-based studies in blacks have firmly established only age and cigarette smoking as risk factors for COPD other than asthma. In 1987, 43% of black men aged 45 and older smoked cigarettes compared to only 30% of white men. Further research is needed on racial From the Office of Analysis and Epidemiology, National Center for Health Statistics, Hyattsville, Maryland. Requests for reprints should be addressed to Dr Richard F. Gillum, Office of Analysis and Epidemiology, National Center for Health Statistics, Presidential Bldg, Rm 1000, 6725 Belerest Road, 3700 East West Hwy, Hyattsville, MD 20782. JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 83, NO. 5
differences in pulmonary function and the effects of multiple risk factors to enhance understanding of COPD etiology and prevention. More vigorous smoking prevention and cessation efforts should be targeted for blacks by physicians and public health organizations. (J Nati Med Assoc. 1991;83:393-401.) Key words * spirometry * Lung volume measurements * Smoking
Chronic obstructive pulmonary disease (COPD) and asthma are significant causes of morbidity and mortality in blacks." 2 Pulmonary function testing is essential in managing and investigating these conditions, and assessing risk factors is essential in managing, preventing, and investigating COPD. Smoking prevention or cessation is all the more urgent in individuals with abnormal pulmonary function, COPD symptoms, or nonmodifiable risk factors for COPD. Many published studies have reported lower lung volumes in blacks compared to whites at all ages."2 These racial differences and their relationship to racial differences in COPD have been inadequately studied. A further unresolved question is whether racial differences in known or suspected risk factors in COPD can explain racial differences in disease occurrence. This article examines racial differences in pulmonary function and risk factors for COPD in blacks that may explain racial differences in COPD using national data from the National Center for Health Statistics (NCHS) 393
CHRONIC OBSTRUCTIVE PULMONARY DISEASE
Milliliters 6000_
6000iliters
----
. ...
5000 _
---
*vs
White men Black men White women
Black women
40003000
Milliliters 5000
----
.
4000
3000
.
...
White men Black men White women Black women
..........
f
*..~~~~~~~I 3000.
2000
..
2000
1000
01~
0 30
40
50
60
70
Age
Figure 1. Mean forced vital capacity (FVC) of black and white adults who never smoked ages 25 to 74 years, reproducible best trial only, by sex and age: United States, 1971.75.6 Note: Mean for black men ages 35 to 44 has a standard error greater than 15% and should be interpreted with caution.
and other previously published reports, with emphasis given to population-based studies.3
PULMONARY FUNCTION Estimates of spirometric function for US adults were obtained in the first National Health and Nutrition Examination Survey (NHANES 1).4-6 However, satisfactory data were obtained in only 25% to 67% of blacks in the sample, with the lowest rates occurring in black women aged 55 to 74 years.6 Satisfactory data were obtained in 48% to 88% of whites. Forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) were lower in blacks than in whites in NHANES I both in smokers and in nonsmokers in almost all age and sex groups (Figures 1 and 2). There were no consistent racial differences in FEV,/FVC.6 The highly effort-dependent measures, peak flow rate and maximal expiratory flow rate were consistently lower in blacks than in whites in smokers and nonsmokers in every age and sex group. However, flow rates were not adjusted for initial volumes. Differences were much less for the effort-independent forced expiratory flow rate at 75% of forced vital capacity, suggesting racial differences in participants' efforts in response to the NHANES I protocol. These NHANES I data were based on results from reproducible best trials for which overall response rates and numbers of participants in age strata were low for blacks. The data must be viewed with caution because 394
.....
30
40
50
60
70
Age
Figure 2. Mean forced expiratory volume at I second (FEV1) of black and white adults who never smoked ages 25 to 74 years, reproducible best trial only, by sex and age: United States, 1971-75.6 Note: Means for black men ages 35 to 44 and 45 to 54 have standard errors greater than 25% and should be interpreted with caution.
of potential bias, similar to most other published spirometric data. The effects of controlling height, weight, body mass index, education, income, region, and other variables on racial differences have not yet been published for NHANES I. Although no thorough analysis has been published on NHANES I data, examination of published tables indicates that unadjusted differences between smokers and nonsmokers in mean FEV1 were consistently greater for whites than for blacks and the decline in mean FEV1 with age in smokers was greater for whites than blacks whether expressed as mL/year or as percent of FEVy for ages 25 to 34 years.6 The NCHS also has published spirometric data for children aged 6 to 11 years who were surveyed from 1963 to 1965.7 In the Health Examination Survey Cycle II (HES II), black boys aged 6 to 11 had lower FVC than white boys the same ages. Differences were greatest at 9 to 11 years. Black girls had consistently lower FVC than white girls. Sex differences were less consistent in blacks than whites. The average black-white difference was about 10% to 15%. The average difference was 236 mL for boys, 186 mL for girls, and 226 mL for both sexes. Black-white differences were most consistent when examined by height rather than age, curves being more nearly parallel for each group.7 However, when sitting height was used, the racial difference was decreased by approximately half. This presumably JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 83, NO. 5
CHRONIC OBSTRUCTIVE PULMONARY DISEASE
TABLE 1. MEAN (SE) LUNG FIELD AREAS* FROM POSTERIOR-ANTERIOR (PA) AND LATERAL CHEST X-RAYS IN A NATIONAL SAMPLE OF WHITES AND BLACKS PA Lateral Age White Black White Black Men 25 to 34 479.22 443.31 405.24 386.95 4.34 8.93 3.22 6.88 35 to 44 472.59 422.27 416.28 374.81 4.69 15.56 3.54 10.44 45 to 54 464.94 439.44 431.18 384.09 4.27 7.56 3.36 8.17 55 to 64 467.23 447.63 451.79 410.94 4.20 10.41 3.81 9.29 65 to 74 461.89 463.59 455.80 397.39 3.84 7.38 3.83 8.50 Women 25 to 34 409.90 366.71 318.27 296.23 2.94 6.08 3.08 3.67 35 to 44 418.18 364.84 336.55 306.56 2.69 6.97 2.20 5.68 45 to 54 408.72 357.17 349.57 322.18 3.13 5.66 2.25 7.06 55 to 64 379.15 339.50 356.41 324.96 3.06 7.21 2.50 7.13 65 to 74 362.74 332.83 359.67 336.02 3.11 7.11 2.97 6.50
*From planimetry,
Cm2.
relates to the lower sitting heights in blacks compared to whites and to the relationship of lung volume to the size and shape of the thorax. However, in individual children, sitting height was not more highly correlated with FVC than with standing height.7 Limitations of these data discussed elsewhere include the exclusion of 1129 of 6932 (16%) spirograms as technically unsatisfactory, differential exclusion rates by race, and unavailability of FEV1 and maximal mid-expiratory flow rate due to technical difficulties.7'8 However, racial differences in FVC were probably estimated fairly accurately. Unfortunately, spirometry data were not available from HES Cycle III in 12 to 17 year olds.7-9 When analyzed and published, data from NHANES II will provide spirometry data for 6 to 24 year olds examined between 1976 and 1980. 10 In NHANES I, internal chest measurements from x-rays of a subsample of adults and a number of anthropometric measurements were available that might have shed light on racial lung volume differences from this national sample.4"'1 Tables 1 and 2 show mean lung field areas by planimetry'2 for 5608 whites and 840 blacks, and thoracic diameters in 2937 whites and 575 blacks by race, age, and sex. In these weighted analyses, blacks in the sample had smaller lung field JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 83, NO. 5
areas and thoracic diameters than whites. Greater racial differences in diameters were obtained in a comparison of European and African miners due to the small overall size of the Africans.13 Total lung capacity (TLC), residual volume (RV), and RV/TLC calculated from NHANES I x-ray data have been published previously.'4 Blacks had a lower mean TLC than whites in all age and sex subgroups. Consistent racial differences were not observed for RV or RV/TLC. Prediction equations were presented for blacks and whites. As in children, the ratio of sitting to standing height was lower in black adults than in white adults.7"15'18 Sitting heights were consistently lower in blacks than in whites with little difference in standing height. In NHANES I, chest circumference at full expiration was not consistently different in black men compared to white men but was greater in black women than in white women, perhaps due to greater obesity in black women. At full inspiration, chest circumference was slightly smaller in black men than in white men but remained greater in black women than in white women. Available data suggest that at least some of the black-white difference in lung volume in adults is associated with a similar difference in thoracic capacity. Numerous other published reports spanning more 395
CHRONIC OBSTRUCTIVE PULMONARY DISEASE
TABLE 2. MEAN (SE) THORACIC DIAMETERS* FROM POSTERIOR-ANTERIOR AND LATERAL CHEST X-RAYS IN A NATIONAL SAMPLE OF WHITES AND BLACKS Lateral 2* Lateral It Transverse White Black Black White White Black Age Men 17.96 30.55 18.75 17.97 18.81 25 to 34 31.52 0.71 0.16 0.38 0.34 0.15 0.16 31.27 19.25 17.90 19.37 17.95 31.67 35 to 44 0.46 0.16 0.45 0.16 0.48 0.16 30.05 19.67 18.10 19.81 18.10 31.66 45 to 54 0.38 0.13 0.34 0.15 0.39 0.15 18.50 31.72 20.21 18.55 20.31 30.54 55 to 64 0.17 0.17 0.33 0.14 0.37 0.32 31.21 30.67 20.02 17.54 20.07 17.55 . 65 to 74 0.43 0.37 0.17 0.41 0.16 0.11 Women 14.87 27.20 26.56 15.21 14.82 15.10 25 to 34 0.11 0.27 0.12 0.30 0.28 0.15 15.35 27.65 27.00 15.89 15.41 15.79 35 to 44 0.12 0.39 0.36 0.13 0.38 0.12 27.08 16.54 16.49 16.46 16.40 27.29 45 to 54
