There are many reports of differences in lung function between people of different ethnic origins. In most of these, white people have been shown to be able to blow out more air, and with more speed, than other people of the same sex, height and age. This is important because predicted values of lung function are usually based on measurements made in white people, which means that when we assess a person from a different ethnic group we run the risk of categorising them as having reduced lung function when, in fact, their measurements are normal for their ethnicity.
Using measurements from children and young people in the cohorts, we set out to see if we also found differences between white and south Asians and, if so, whether we could explain such differences to socioeconomic, environmental or cultural factors, or to differences in asthma, wheezing, or anything relating to birth.
We studied 1088 white and 275 UK-born south Asian children aged 9-14 years. From their lung function measurements we showed that the white children could blow out more than their south Asian counterparts (i.e. their lungs are about 10% bigger), but that the flows were very similar. This is in line with findings of other groups. Our study was able to show that the differences did not appear to be due to any environmental, social, or cultural factors, nor to differences in the amount of asthma or wheezing. We conclude that the differences are likely to be genetic, and that south Asian children should have their own set of predicted values for lung function. This contrasts with a general move towards ‘multi-ethnic’ predicted values, and we are continuing to explore this topic in detail.
Strippoli MP, Kuehni CE, Dogaru CM, Spycher BD, McNally T, Silverman M, Beardsmore CS. Etiology of ethnic differences in childhood spirometry. Pediatrics. 2013; doi: 10.1542/ peds. 2012-3003.