Lung function and ethnicity
People are allocated to different ethnic groups on the basis of differences in skin colour, physical characteristics and geographical location. In Europe one deals mostly with Caucasians, Negroid, Mongoloid and Polynesian people, and those from the Indian subcontinent. Ethnic differences in lung function are in part due to differences in body build. The lungs are contained in the thorax, so that it would be logical to predict lung volumes from the dimensions of the chest cage or trunk. In practice predictions are based on total standing height, i.e. including the skull, neck, thoracic and lumbar spine, and legs. For the same length Negroid people usually have shorter trunks than Caucasians, whilst Mongoloid people have a longer trunk (ref. 1). Therefore prediction equations for Caucasians are not necessarily valid for other ethnic groups. One should keep in mind that even among black people there are important differences in body build. There are differences between white and black people in the relationship between sitting and standing height. Similar differences have been noted between Ethiopians and Japanese.
There is no evidence for differences in lung function among Caucasians in Europe. In general, in people of mixed ethnic descent lung volumes are intermediate between that of the parents’ ethnic groups (ref. 2).
Differences in lung function between inhabitants of the northern and southern part of the Indian subcontinent are attributed to diet and ethnic admixture. A protein rich diet leads to an increased body size, and there is some evidence that with the adoption of a western lifestyle differences in lung function with Caucasians diminish. Ethnic admixture similarly causes differences to become smaller.
The Global Lung Function Initiative addressed ethnicity by expanding the equation on the previous page as follows:
log(Y) = a + b•log(height) + c•log(age) + ethnic group + spline
where ethnic group takes a value of either 0 or 1 for Caucasian, African American, North East Asian or South East Asian.
FEV1%FVC is by and large independent of ethnic group; as shown for females in the graph, same finding in males. The practical implication is that differences in FEV1 and FVC between ethnic groups are proportional, underlining that the design of the lung is the same, but that there are just some scale differences. Thus, compared to white females, differences in FEV1 are as follows:
|North East Asia||- 1.5%|
|South East Asia||-11.4%|
|Ref. 1 - Leg length and sitting height|
|Negroid subjects in general have longer legs for trunk height:|
|1||Verghese KP, Scott RB, Teixeirea G, Ferguson AD. Studies in growth and development. XII. Physical growth of northern American Negro children. Paediatrics 1966; 44: 243-247.|
|2||Van de Wal BW, Erasmus LD, Hechter R. Stem and standing heights in Bantu and white South Africans: their significance in relation to pulmonary function values. S Afr J Lab Clin Med 1971; 45 (suppl.): 568-570.|
|3||Rossiter CE, Weill H. Ethnic differences in lung function: evidence for proportional difference. Intern J Epidem 1974; 3: 55-61.|
|4||Quanjer PH, Stocks J, Cole TJ, Hall GL, Stanojevic S. Influence of secular trends and sample size on reference equations for lung function tests, Eur Respir J 2011; 37: 658–664.|
|5||Bibi H, Goldsmith JR, Vardi H. Racial or ethnic variation in spirometric lung function norms. Recommendations based on study of Ethiopian Jews. Chest 1988; 93: 1026-1030.|
|6||Massey DG, Fournier-Massey G. Japanese-Americans pulmonary reference values: influence of environment on anthropology and physiology. Env Res 1986; 39: 418-433.|
|Ref. 2 - Genetic and ethnic factors|
|1||Reed TE. Caucasian genes in American Negroes. Science 1969: 165: 762-768.|
|2||Kumar R, Seibold MA, Aldrich MC, et al. Genetic ancestry in lung-function predictions. N Engl J Med 2010; 363: 321-330.|