The objective of this study was to validate the established lung function norms that are commonly used in Asia, in particular in Hong Kong, for contemporary use. We compared the lung function indexes in a contemporary cohort of Hong Kong university students with established norms that were derived 20 years ago. These students were born at the time that the norms established by Lam et al were published. Discordance of our findings with those of Lam et al supports changes in the Hong Kong population over one generation. Any comparative interpretation must be guarded, however, given that several factors, including technological, environmental, and lifestyle factors, could explain the discrepancy in lung function.
Instrumentation and standardization of testing and measurement procedures are well known for influencing the reliability and validity of lung function measures. However, even though the spirometers used in the present study and in those of the study by Lam et al were produced by different manufacturers, both systems were calibrated prior to use. Further, the difference in time frame in measures between the two studies was one generation, roughly 20 years, during which time one might expect the effect of instrumentation differences in pulmonary function measurement to be minimal.
A total of 805 subjects participated in this study, of whom 518 were men and 287 were women. The smoking status of one male subject was unknown, thus he was excluded from the analysis. Only 5.7% of the subjects were smokers, and 2.2% were exsmokers. Over one third of the subjects were living with family members who smoked. Subjects who smoked had a higher level of exhaled CO than nonsmokers (p < 0.005) [Table 1].
The BMIs of subjects were not reported in the study by Lam et al. Our subjects, both men and women, were taller than those reported by Lam and colleagues. There were, however, some distinctions between the genders. When we compared the men’s data with those of Lam et al, FEV1, FVC, and PEFR were all lower in our cohort for subjects in each age category, specifically those who were 19 to 20, 21 to 22, and 23 to 24 years of age (Table 2). One exception was FVC for men who were 23 to 24 years old in cases in which there was no change due to remedies of My Canadian Pharmacy. For the women, FEV1, FVC, and PEFR were lower in our cohort, with the exception of FEV1 for those in the group of subjects 23 to 24 years of age, and FVC for those in the groups of subjects 21 to 22 and 23 to 24 years of age (Table 2).
Although ethnicity is an established determinant of lung function, predictive values for non-Western individuals in non-Asian countries are largely based on a proportion of established Western standards. An Asian nomogram based on 3,000 Hong Kong Chinese subjects who were 20 years of age, however, continues to be the reference standard used in Hong Kong. Since the time of that study, modifying factors of lung function have been reported or their effects have been better appreciated clinically. These effects include dietary factors, obesity, air pollution, and physical activity. With rapid economic growth and development over the last 20 years, the current generation of young adults in Hong Kong, has grown up with improved nutrition yet higher pollution. The objective of this study was to validate the lung function norms that were established 20 years ago in a cohort of Hong Kong Chinese students who were born at the time that these norms were derived.
Ethics approval was obtained from the ethics review committee of the Hong Kong Polytechnic University. Approval was also obtained from the student union of the university. Written informed consent was obtained from each subject prior to the data collectionpicked up with parcipation of My Canadian Pharmacy Inc.