Spirometry of healthy adult South African men. Part II. Interrelationship between socio-environmental factors and 'race' as determinants of spirometry.

AIM

To examine the interaction of socio-environmental background, 'race' and anthropometry on spirometry.

METHODS

A study population of white and black bank workers with broadly comparable current socio-economic circumstances was identified. Detailed questionnaires regarding a number of indicators of socio-environmental status (SES) were administered in addition to anthropometric and spirometric measurements. Multiple linear regression analyses were performed. The Kappa statistic was used to determine the best predictors of SES.

RESULTS

'Race' was found to be the best predictor of SES. Within the black group a sub-classification of high and low SES was possible. In all respects the white SES indicators were higher than those of the black high SES group. Multiple regression analysis showed that sitting height was a better anthropometric predictor of spirometry than standing height. Replacing 'race' with other indicators of SES gave similar measures of prediction (by Mallow's CP statistic) of spirometry in the over-30-year age group.

CONCLUSION

The impact of 'race' on spirometry can be reduced substantially by incorporating sitting height and indicators of SES in the regression equations. This observation lends support to the hypothesis that 'race' is not a direct genetic predictor of lung size, but may have an influence because of SES and anthropometric features associated with 'race'.