Lung Function among Black and White Children'-· RALPH E. BINDER, CHARLES A. MITCHELL, JANET B. SCHOENBERG, and AREND BOUHUYS
SUMMARY ________________________________________________________ Racial differences in ventilatory lung function were evaluated in a community study of 393 children (158 blacks, 235 whites). Mean forced vital capacity was 18 per cent larger in nonsmoking white males than in nonsmoking black males, and Il per cent larger in nonsmoking white females than in nonsmoking black females. Similar differences were observed for the l·sec forced expiratory volume and for the maximal expiratory flow at 50 per cent of the forced vital capacity. However, when adjusted for lung size (on the basis of forced vital capacity), 1-sec forced expiratory volume and maximal expiratory flow at 50 per cent of the forced vital capacity were larger in the black children compared to the white children. Lung function prediction equations based on race, sex, age, height and weight are presented for healthy nonsmoking children; these allow for an evaluation of normal lung function in both black and white children.
Introduction Several investigators have described differences in ventilatory lung function between the black and white races (l-6). Most studies have concentrated on adult populations, showing that (1) whites have a larger forced vital capacity (FVC) and l-sec forced expiratory volume (FEV1 ) than blacks (l-3); (2) blacks have a FEV 1 j:FVC ratio equal to or larger than that of whites (1-3). In the 1920s it was shown that the vital capacity of white children was larger than that of black children of similar age, height, and weight (46). Since then one study has reported ventilatory lung function among healthy black children (7). To clarify racial differences in lung function and in the natural history of chronic lung disease, it is advantageous to use children as sub(Received in original form june 1, 1976 and in revised form August 11, 1976) 1 From the Yale University Lung Research Center, 333 Cedar St., New Haven, Conn. 06510. 2 This research was partially supported by Contract NOl-HR-4-2912 and by SCOR grant HL14179 from the National Heart and Lung Institute. 3 Requests for reprints should be addressed to Dr. Arend Bouhuys at the above address.
jects because most have never smoked cigarettes regularly, they usually have lived only in the area of study, and any racial differences observed have not been influenced by occupational exposures. In the present study we examined racial differences in ventilatory lung function in nonsmoking healthy children living in a defined community. In addition, we present lung function prediction equations for healthy black children and white children.
Materials and Methods From April through June 1973, 393 children 9 to 17 years of age were examined at a mobile laboratory as part of a community respiratory disease survey in the fourth ward of Ansonia, Connecticut, an industrial community. All data were collected with an on-line digital computer system. A standardized questionnaire was administered to all subjects by trained interviewers to collect information on respiratory symptoms and smoking hab· its. Children were classified as asymptomatic if they did not report usual cough, usual sputum produc· tion, or frequent wheeze. The term nonsmoker is used to describe children who have never smoked cigarettes regular! y. Ventilatory function was assessed by recording the relation between flow and volume during a maximal
AMERICAN REVIEW OF RESPIRATORY DISEASE, VOLUME 114, 1976
955
956
BINDER, MITCHELL, SCHOENBERG, AND BOUHUYS
20
TABLE 1
!210
~
MEAN HEIGHT, WEIGHT, AND AGE OF THE NONSMOKING ASYMPTOMATIC CHILDREN
1l
:E
BY RACE AND SEX
3:
*
d'~
10
fl)
Subjects
n
Black Males Females
46 49
153 ± 16 155 ± 11
44 ± 15 51 ± 17
12 ± 2.4 12 ± 2.3
White Males Females
73 87
151 ±17 152 ± 11
45 ± 16 48 ± 15
12 ± 2.5 13 ± 2.7
Weight (kg) ±SD
x ±SD
x
·e" c
Height (em) x ±SD
Age
(years)
t
0
..>C
u
0
iii .; u
forced expiration. Flow rate was measured with a pneumotachygraph and expired volume was obtained by digital integration of flow. Interviewers determined if a forced expiration was acceptable by viewing the flow-volume curve on a computer-terminal screen. Of 5 acceptable efforts, the 2 with the highest FEV1 were averaged and stored for analysis. If the percentage difference between the 2 highest FEV 1 values was ~ 10.0 per cent, the lung function data for that subject were not used in the analysis. Three subjects were excluded for that reason. Numerical data from the flow-volume curve included FVC, FEV1 , and instantaneous maximal expiratory flow at 50 per cent of the FVC (Vmax 50).
f-10
£
0
-20
FVC
*
FEV1.0
FEV1.o FVC
MEF50%
MEF50%
FVC"
Fig. 1. Per cent difference in mean lung function indices between black and white children 9 to I 7 years of age. Bars above the line indicate larger values in blacks; bars below the line indicate larger values in whites. Symbols indicate significant black-white differences (*P < 0.05, tP < 0.01, :j:p < 0.001). FVC = forced vital capacity; FEV 1•0 = 1-sec forced expiratory volume; MEF 50% (Vmax 50 ) = maximal expiratory flow at 50 per cent of forced vital capacity.
Results
Data were collected on 393 (85 per cent) of the 462 children, 9 to 17 years of age, living in the fourth ward of Ansonia at the time of the study. Lung function data from nonsmoking asymp-
TABLE 2 LUNG FUNCTION PREDICTION EQUATIONS FOR NONSMOKING, ASYMPTOMATIC CHILDREN 9 TO 17 YEARS OF AGE BY RACE AND SEX Regression Coefficients" Subjects Black Males
Females
White Males
n
Index
b Height
c Weight
d Age
SEE
R2t
46
FVC, liter FEVt. liter Vmax 5 o. liter/sec
2.33 2.11 3.18
-2.10 -2.43 -6.56
0.013 0.017 0.051
0.026 0.008 -0.024
0.108 0.133 0.247
0.356 0.286 0.761
0.85 0.86 0.69
49
FVC, liter ~EV 1• liter Vmax 5 o. liter/sec
2.37 2.10 3.19
-3.30 -2.93 -3.43
0.032 0.029 0.036
0.011 0.006 0.004
0.016 0.014 0.064
0.385 0.272 0.744
0.69 0.74 0.40
FVC, liter
2.86 2.48 3.26
-3.89 -3.35 -2.76
0.036 0.030 0.025
0.018 0.009 0.008
0.046 0.076 0.158
0.399 0.291 0.563
0.86 0.89 0.73
2.67 2.39 3.38
-3.38 -3.52 -5.68
0.031 0.033 0.052
0.010 -0.001 -0.020
0.065 0.076 0.169
0.368 0.296 0.607
0.75 0.78 0.64
73
~EV 1 ,.1iter
Females
Mean
a Intercept
87
Vmax 5 o. liter/sec FVC, liter ~EV1,Iiter
Vmax 50 , liter/sec
Definition of abbreviations: SEE = standard error of the estimate; FVC =forced vital capacity; FEV 1 = 1-sec
forced expiratory volume; Vmax 50 =maximal expiratory flo~ at 50 per cent of the forced vital capacity. *Intercept and coefficient in equations: FVC, FEV1.0• or Vmaxso =a+ b X height (em)+ c X weight (kg)+ d X age (years). t R 2 = proportion of the variance in FVC, FEVt. or Vmax 50 that is explained by the regression line. P < 0.01 for all R2 displayed.
957
RACIAL DIFFERENCES IN LUNG FUNCTION
tomatic children were analyzed both by comparison of means, using the "Student's" t test, in sex and rate subgroups, and by multiple regression analysis. :Vfean height, weight, and age of the children whose data were used in this analvsis are presented in table 1. \\'ithin each sex group there were no significant racial differences in mean age, height, or weight. :VIean FVC and mean FEV1 were significantly larger in whites than in blacks among both sexes (figure 1). In contrast, when FEV1 was adjusted for lung size and expressed as FEVIfFVC, the racial difference almost disappeared among the females and reversed among the males. Mean Vmax 50 was larger in the white than in the black children in both sexes. On the other hand, the volume-adjusted flow measurement (Vmax 50 jFVC) was larger in the blacks, particularly in the males. ?vlultiple regression analysis confirmed the racial differences in mean lung function. Lung function prediction equations for nonsmoking, asymptomatic children by sex and race subgroup are shown in table 2. All regressions on height, weight, and age were highly significant. Among the males, more than 80 per cent of the variance in FVC and FEV 1 and approximately 70 per cent of the variance in Vmax 50 were explained by the regression equations. In contrast, among the females smaller proportions of the variance were explained by the regressions. To compare the regression lines over the range of age, height, and weight included, each lung function index was plotted as a function of one independent variable and standardized for the 2 remaining variables. A sample of these comparisons is shown in figure 2 for FVC and Vmax 50 in relation to height. Overall, this analysis supports the statement that white children had larger FVC and FEV1 than black children of equivalent height, weight, and age. Of note is that the males had an increasing difference in FVC (and FEV1 ) over the height range studied, whereas the females had a more fixed difference. Among the females, Vmax 50 was larger in whites than in blacks, except for the youngest shortest children, whereas among the males this trend was reversed in the older taller children where Vmax 50 was larger in the blacks. Multiple linear regression analysis of data from all the children showed that race was a significant predictor of FVC, FEV 1 , and Vmax 50 independent of age, height, weight, sex, and smoking status.
Discussion
\Ve observed significant racial differences in ventilatory lung function among nonsmoking, asymptomatic children. Larger vital capacities in white children compared to black were first observed in the 1920s (4-6); a recent study showed this to be true in females but not in males (7). Racial differences in FEV 1 and Vmax 50 in children have not previously been reported. Our findings in FVC and FEV1 are similar in direction and magnitude to those consistently found in adults from several geographic areas (2, 8, 9). It seems unlikely that differences in socioeconomic status would explain such consistent observations from all locations. It is also unlikely that socioeconomic factors affecting growth influenced the data because there were no significant differences in height or weight between the black and white children (table 1). In part, the racial differences in lung size may be explained by the smaller ratio of sitting height to standing height in blacks compared to whites (10). If there were significant differences in the ratio of residual volume (R V) to total lung capacity (TLC) between black and white children it would partially explain the differences in lung
Females
Males
5 ~4
2!
63 u
>
LL.
2
]5 ~
~
§ ~ 0
0
ll)
LL.
I.LJ ~
4 3
2 I
"7 ------W: -2.5 + 0.036(H)
w:-0.5+0.025(Hl 8 :-4.7+0.051 (H)/
/ /
/
130 150 170 190
W:-2.1+0.031 (H) 8:-2.6+0.032(H)
/' /
/
//
W:-4.5+0.052(H) 8 :-2.4+0.036(H)
130 150 170 190
Height (em)
Fig. 2. The relationships between forced vital capacity (FVC) and height and maximal expiratory flow at 50 per cent of forced vital capacity (MEF 50%) and height, for black(---) and white(--) children 9 to 17 years of age. Equations are standardized with the weighted mean for age and weight using weight = 44.58 kg and age = 11.96 years for males, and weight = 48.78 kg and age =12.65 years for females.
958
BINDER, MITCHELL, SCHOENBERG, AND BOUHUYS
TABLE 3 COMPARISON OF PREDICTED LUNG FUNCTION INDICES FOR WHITE CHILDREN, BY SEX AND AGE, USING DIFFERENT PREDICTIONS EQUATIONS* Dickman Subjects Males 9-12 years
Study
( 11) t
( 12) ••
FVC, liter
2.34
2.21
2.42
FEV 1 , liter
2.02 2.72
1.89 2.63
1.93 3.11
FVC, liter
4.11
4.29
4.37
FEV 1 , liter
3.51 4.41
3.63 4.53
3.48 4.75
~EV 1• liter Vmax 50 , liter/sec
2.10 1.95 2.76
1.97 1.67 2.51
2.30 2.17 3.04
FVC, liter FEV1, liter Vmax 5 o. liter/sec
3.11 2.83 4.02
3.00 2.61 3.58
3.02 2.76 3.76
Vmax 50 , liter/sec Females 9-12 years
13-17years
eta/.
eta/.
Vmax 50 , liter/sec 13-17 years
Zap leta I
Present
Lung Function Indices
FVC, liter
*Average values of height, weight, and age for the white children seen in this survey were used to obtain the indices. tPrediction equations were based on 950 healthy, normal children (482 boys, 468
girls) 5 to· 18 years of age. **Prediction equations were based on 65 healthy children (39 boys, 26 girls) 6 to 18 years of age.
function we observed and make the use of FVC to adjust for lung size less reliable. Rossiter and Weill (9) compared RV, TLC, and RVJTLC in black and white adults. They found that although the RV fTLC ratio was slightly larger among black adults, the difference was not significant (P < 0.05). The racial differences in lung volumes and flow rates described may also be explained if the elastic recoil of the lungs of black children is greater than that of white children. Increased recoil would result in decreased TLC and vital capacity. It would also result in increased airway support and, hence, larger airway caliber at any given lung volume. This might explain the larger FVC and FEV1 of whites as well as the larger FEV 1 JFVC and Vmax 50 jFVC observed in blacks. However, no comparable data on lung elastic recoil in blacks and whites are available to substantiate this explanation. Our equations relating lung function indices to age, height, and weight for healthy nonsmoking children of both races explain a major proportion of the variance of these indices. The prediction equations for lung function of white children obtained in previous investigations (11. 12) are similar to ours (table 3).
W'e observed an increasing racial difference in FVC and FEV 1 with height among males, whereas the females showed a more fixed difference. Perhaps growth among white males is marked hy an increased ratio of sitting to standing height compared to black males. If this is true, the lack of a similar pattern in females is unexplained. \\'hen ventilatory lung function tests are used in the assessment of childhood lung disease, it is essential that "normal" values be standardized for race. The prediction equations for black children presented in this paper can be used for this purpose in conjunction with those from this or previous studies of white children. Acknowledgment
We are indebted to Peter Snyder, Jim Virgulto, Lynn Newman, and the residents of Ansonia's fourth ward for their help with this survey.
References I. Abramowitz, S., Leiner, G. C., Lewis, W. A., and Small, M. J.: Vital capacity in the Negro, Am Rev Respir Dis, !965, 92,287. 2. Lapp, N. L.. Amandus, H. E., Hall, R., and Morgan, W. K. C.: Lung volumes and flow rates in black and white subjects, Thorax, 1974, 29, 185. 3. Oscherwitz, M., Edlavitch, S. A., Baker, T. R.,
RACIAL DIFFERENCES IN LUNG FUNCTION
4.
5. 6.
7.
8.
and Jarboe, T.: Differences in pulmonary functions in various racial groups, Am J Epidemiol, 1972,96,319. Roberts, F. L., and Crabtree, J. A.: The vital capacity of the Negro child, JAMA, 1927, 88, 1950. Smillie, W. G., and Augustine, D. L.: Vital capacity of the Negro race, JAMA, 1926, 87, 2055. Wilson, M. G., and Edwards, D. J.: Diagnostic value of determining vital capacity of lungs of children, JAMA, 1922,78, II07. Chehreh, M. N., Young, R. C., Viaene, H., Ross, C. W., and Scott, R. B.: Spirometric standards for healthy inner-city black children, Am J Dis Child, 1973, 126, 159. Femi-Pearse, D., and E!ebute, E. A.: Ventilatory
9.
10. II.
12.
959
function in healthy adult Nigerians, Clin Sci, 1971,41,203. Rossiter, C. E., and Weill, H.: Ethnic differences in lung function: Evidence for proportional differences, Int J Epidemiol, 1974,3, 55. Damon, A.: l\egro-white differences in pulmonary function, Hum Bioi, 1966,38, 380. Dickman, M. L., Schmidt, C. D., and Gardner, R. M.: Spirometric standards for normal children and adolescents (ages 5 years through 18 years), Am Rev Respir Dis, 1971,104, 680. Zapletal, A., Motoyama, E. F., Van de Woestijne, Hunt, V. R., and Bouhuys, A.: Maximum expiratory flow volume curves and airway conductance in children and adolescents, J Appl Physiol, 1969, 26,308.
SUMMARY ________________________________________________________ Racial differences in ventilatory lung function were evaluated in a community study of 393 children (158 blacks, 235 whites). Mean forced vital capacity was 18 per cent larger in nonsmoking white males than in nonsmoking black males, and Il per cent larger in nonsmoking white females than in nonsmoking black females. Similar differences were observed for the l·sec forced expiratory volume and for the maximal expiratory flow at 50 per cent of the forced vital capacity. However, when adjusted for lung size (on the basis of forced vital capacity), 1-sec forced expiratory volume and maximal expiratory flow at 50 per cent of the forced vital capacity were larger in the black children compared to the white children. Lung function prediction equations based on race, sex, age, height and weight are presented for healthy nonsmoking children; these allow for an evaluation of normal lung function in both black and white children.
Introduction Several investigators have described differences in ventilatory lung function between the black and white races (l-6). Most studies have concentrated on adult populations, showing that (1) whites have a larger forced vital capacity (FVC) and l-sec forced expiratory volume (FEV1 ) than blacks (l-3); (2) blacks have a FEV 1 j:FVC ratio equal to or larger than that of whites (1-3). In the 1920s it was shown that the vital capacity of white children was larger than that of black children of similar age, height, and weight (46). Since then one study has reported ventilatory lung function among healthy black children (7). To clarify racial differences in lung function and in the natural history of chronic lung disease, it is advantageous to use children as sub(Received in original form june 1, 1976 and in revised form August 11, 1976) 1 From the Yale University Lung Research Center, 333 Cedar St., New Haven, Conn. 06510. 2 This research was partially supported by Contract NOl-HR-4-2912 and by SCOR grant HL14179 from the National Heart and Lung Institute. 3 Requests for reprints should be addressed to Dr. Arend Bouhuys at the above address.
jects because most have never smoked cigarettes regularly, they usually have lived only in the area of study, and any racial differences observed have not been influenced by occupational exposures. In the present study we examined racial differences in ventilatory lung function in nonsmoking healthy children living in a defined community. In addition, we present lung function prediction equations for healthy black children and white children.
Materials and Methods From April through June 1973, 393 children 9 to 17 years of age were examined at a mobile laboratory as part of a community respiratory disease survey in the fourth ward of Ansonia, Connecticut, an industrial community. All data were collected with an on-line digital computer system. A standardized questionnaire was administered to all subjects by trained interviewers to collect information on respiratory symptoms and smoking hab· its. Children were classified as asymptomatic if they did not report usual cough, usual sputum produc· tion, or frequent wheeze. The term nonsmoker is used to describe children who have never smoked cigarettes regular! y. Ventilatory function was assessed by recording the relation between flow and volume during a maximal
AMERICAN REVIEW OF RESPIRATORY DISEASE, VOLUME 114, 1976
955
956
BINDER, MITCHELL, SCHOENBERG, AND BOUHUYS
20
TABLE 1
!210
~
MEAN HEIGHT, WEIGHT, AND AGE OF THE NONSMOKING ASYMPTOMATIC CHILDREN
1l
:E
BY RACE AND SEX
3:
*
d'~
10
fl)
Subjects
n
Black Males Females
46 49
153 ± 16 155 ± 11
44 ± 15 51 ± 17
12 ± 2.4 12 ± 2.3
White Males Females
73 87
151 ±17 152 ± 11
45 ± 16 48 ± 15
12 ± 2.5 13 ± 2.7
Weight (kg) ±SD
x ±SD
x
·e" c
Height (em) x ±SD
Age
(years)
t
0
..>C
u
0
iii .; u
forced expiration. Flow rate was measured with a pneumotachygraph and expired volume was obtained by digital integration of flow. Interviewers determined if a forced expiration was acceptable by viewing the flow-volume curve on a computer-terminal screen. Of 5 acceptable efforts, the 2 with the highest FEV1 were averaged and stored for analysis. If the percentage difference between the 2 highest FEV 1 values was ~ 10.0 per cent, the lung function data for that subject were not used in the analysis. Three subjects were excluded for that reason. Numerical data from the flow-volume curve included FVC, FEV1 , and instantaneous maximal expiratory flow at 50 per cent of the FVC (Vmax 50).
f-10
£
0
-20
FVC
*
FEV1.0
FEV1.o FVC
MEF50%
MEF50%
FVC"
Fig. 1. Per cent difference in mean lung function indices between black and white children 9 to I 7 years of age. Bars above the line indicate larger values in blacks; bars below the line indicate larger values in whites. Symbols indicate significant black-white differences (*P < 0.05, tP < 0.01, :j:p < 0.001). FVC = forced vital capacity; FEV 1•0 = 1-sec forced expiratory volume; MEF 50% (Vmax 50 ) = maximal expiratory flow at 50 per cent of forced vital capacity.
Results
Data were collected on 393 (85 per cent) of the 462 children, 9 to 17 years of age, living in the fourth ward of Ansonia at the time of the study. Lung function data from nonsmoking asymp-
TABLE 2 LUNG FUNCTION PREDICTION EQUATIONS FOR NONSMOKING, ASYMPTOMATIC CHILDREN 9 TO 17 YEARS OF AGE BY RACE AND SEX Regression Coefficients" Subjects Black Males
Females
White Males
n
Index
b Height
c Weight
d Age
SEE
R2t
46
FVC, liter FEVt. liter Vmax 5 o. liter/sec
2.33 2.11 3.18
-2.10 -2.43 -6.56
0.013 0.017 0.051
0.026 0.008 -0.024
0.108 0.133 0.247
0.356 0.286 0.761
0.85 0.86 0.69
49
FVC, liter ~EV 1• liter Vmax 5 o. liter/sec
2.37 2.10 3.19
-3.30 -2.93 -3.43
0.032 0.029 0.036
0.011 0.006 0.004
0.016 0.014 0.064
0.385 0.272 0.744
0.69 0.74 0.40
FVC, liter
2.86 2.48 3.26
-3.89 -3.35 -2.76
0.036 0.030 0.025
0.018 0.009 0.008
0.046 0.076 0.158
0.399 0.291 0.563
0.86 0.89 0.73
2.67 2.39 3.38
-3.38 -3.52 -5.68
0.031 0.033 0.052
0.010 -0.001 -0.020
0.065 0.076 0.169
0.368 0.296 0.607
0.75 0.78 0.64
73
~EV 1 ,.1iter
Females
Mean
a Intercept
87
Vmax 5 o. liter/sec FVC, liter ~EV1,Iiter
Vmax 50 , liter/sec
Definition of abbreviations: SEE = standard error of the estimate; FVC =forced vital capacity; FEV 1 = 1-sec
forced expiratory volume; Vmax 50 =maximal expiratory flo~ at 50 per cent of the forced vital capacity. *Intercept and coefficient in equations: FVC, FEV1.0• or Vmaxso =a+ b X height (em)+ c X weight (kg)+ d X age (years). t R 2 = proportion of the variance in FVC, FEVt. or Vmax 50 that is explained by the regression line. P < 0.01 for all R2 displayed.
957
RACIAL DIFFERENCES IN LUNG FUNCTION
tomatic children were analyzed both by comparison of means, using the "Student's" t test, in sex and rate subgroups, and by multiple regression analysis. :Vfean height, weight, and age of the children whose data were used in this analvsis are presented in table 1. \\'ithin each sex group there were no significant racial differences in mean age, height, or weight. :VIean FVC and mean FEV1 were significantly larger in whites than in blacks among both sexes (figure 1). In contrast, when FEV1 was adjusted for lung size and expressed as FEVIfFVC, the racial difference almost disappeared among the females and reversed among the males. Mean Vmax 50 was larger in the white than in the black children in both sexes. On the other hand, the volume-adjusted flow measurement (Vmax 50 jFVC) was larger in the blacks, particularly in the males. ?vlultiple regression analysis confirmed the racial differences in mean lung function. Lung function prediction equations for nonsmoking, asymptomatic children by sex and race subgroup are shown in table 2. All regressions on height, weight, and age were highly significant. Among the males, more than 80 per cent of the variance in FVC and FEV 1 and approximately 70 per cent of the variance in Vmax 50 were explained by the regression equations. In contrast, among the females smaller proportions of the variance were explained by the regressions. To compare the regression lines over the range of age, height, and weight included, each lung function index was plotted as a function of one independent variable and standardized for the 2 remaining variables. A sample of these comparisons is shown in figure 2 for FVC and Vmax 50 in relation to height. Overall, this analysis supports the statement that white children had larger FVC and FEV1 than black children of equivalent height, weight, and age. Of note is that the males had an increasing difference in FVC (and FEV1 ) over the height range studied, whereas the females had a more fixed difference. Among the females, Vmax 50 was larger in whites than in blacks, except for the youngest shortest children, whereas among the males this trend was reversed in the older taller children where Vmax 50 was larger in the blacks. Multiple linear regression analysis of data from all the children showed that race was a significant predictor of FVC, FEV 1 , and Vmax 50 independent of age, height, weight, sex, and smoking status.
Discussion
\Ve observed significant racial differences in ventilatory lung function among nonsmoking, asymptomatic children. Larger vital capacities in white children compared to black were first observed in the 1920s (4-6); a recent study showed this to be true in females but not in males (7). Racial differences in FEV 1 and Vmax 50 in children have not previously been reported. Our findings in FVC and FEV1 are similar in direction and magnitude to those consistently found in adults from several geographic areas (2, 8, 9). It seems unlikely that differences in socioeconomic status would explain such consistent observations from all locations. It is also unlikely that socioeconomic factors affecting growth influenced the data because there were no significant differences in height or weight between the black and white children (table 1). In part, the racial differences in lung size may be explained by the smaller ratio of sitting height to standing height in blacks compared to whites (10). If there were significant differences in the ratio of residual volume (R V) to total lung capacity (TLC) between black and white children it would partially explain the differences in lung
Females
Males
5 ~4
2!
63 u
>
LL.
2
]5 ~
~
§ ~ 0
0
ll)
LL.
I.LJ ~
4 3
2 I
"7 ------W: -2.5 + 0.036(H)
w:-0.5+0.025(Hl 8 :-4.7+0.051 (H)/
/ /
/
130 150 170 190
W:-2.1+0.031 (H) 8:-2.6+0.032(H)
/' /
/
//
W:-4.5+0.052(H) 8 :-2.4+0.036(H)
130 150 170 190
Height (em)
Fig. 2. The relationships between forced vital capacity (FVC) and height and maximal expiratory flow at 50 per cent of forced vital capacity (MEF 50%) and height, for black(---) and white(--) children 9 to 17 years of age. Equations are standardized with the weighted mean for age and weight using weight = 44.58 kg and age = 11.96 years for males, and weight = 48.78 kg and age =12.65 years for females.
958
BINDER, MITCHELL, SCHOENBERG, AND BOUHUYS
TABLE 3 COMPARISON OF PREDICTED LUNG FUNCTION INDICES FOR WHITE CHILDREN, BY SEX AND AGE, USING DIFFERENT PREDICTIONS EQUATIONS* Dickman Subjects Males 9-12 years
Study
( 11) t
( 12) ••
FVC, liter
2.34
2.21
2.42
FEV 1 , liter
2.02 2.72
1.89 2.63
1.93 3.11
FVC, liter
4.11
4.29
4.37
FEV 1 , liter
3.51 4.41
3.63 4.53
3.48 4.75
~EV 1• liter Vmax 50 , liter/sec
2.10 1.95 2.76
1.97 1.67 2.51
2.30 2.17 3.04
FVC, liter FEV1, liter Vmax 5 o. liter/sec
3.11 2.83 4.02
3.00 2.61 3.58
3.02 2.76 3.76
Vmax 50 , liter/sec Females 9-12 years
13-17years
eta/.
eta/.
Vmax 50 , liter/sec 13-17 years
Zap leta I
Present
Lung Function Indices
FVC, liter
*Average values of height, weight, and age for the white children seen in this survey were used to obtain the indices. tPrediction equations were based on 950 healthy, normal children (482 boys, 468
girls) 5 to· 18 years of age. **Prediction equations were based on 65 healthy children (39 boys, 26 girls) 6 to 18 years of age.
function we observed and make the use of FVC to adjust for lung size less reliable. Rossiter and Weill (9) compared RV, TLC, and RVJTLC in black and white adults. They found that although the RV fTLC ratio was slightly larger among black adults, the difference was not significant (P < 0.05). The racial differences in lung volumes and flow rates described may also be explained if the elastic recoil of the lungs of black children is greater than that of white children. Increased recoil would result in decreased TLC and vital capacity. It would also result in increased airway support and, hence, larger airway caliber at any given lung volume. This might explain the larger FVC and FEV1 of whites as well as the larger FEV 1 JFVC and Vmax 50 jFVC observed in blacks. However, no comparable data on lung elastic recoil in blacks and whites are available to substantiate this explanation. Our equations relating lung function indices to age, height, and weight for healthy nonsmoking children of both races explain a major proportion of the variance of these indices. The prediction equations for lung function of white children obtained in previous investigations (11. 12) are similar to ours (table 3).
W'e observed an increasing racial difference in FVC and FEV 1 with height among males, whereas the females showed a more fixed difference. Perhaps growth among white males is marked hy an increased ratio of sitting to standing height compared to black males. If this is true, the lack of a similar pattern in females is unexplained. \\'hen ventilatory lung function tests are used in the assessment of childhood lung disease, it is essential that "normal" values be standardized for race. The prediction equations for black children presented in this paper can be used for this purpose in conjunction with those from this or previous studies of white children. Acknowledgment
We are indebted to Peter Snyder, Jim Virgulto, Lynn Newman, and the residents of Ansonia's fourth ward for their help with this survey.
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