CMAJ • November 18, 2008; 179 (11). doi:10.1503/cmaj.071797.
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Research

Prevalence of asthma among Chinese adolescents living in Canada and in China

Hong-Yu Wang, MD PhD, Gary W.K. Wong, MD, Yu-Zhi Chen, MD, Alexander C. Ferguson, MB ChB, Justina M. Greene, Yu Ma, MD, Nan-Shan Zhong, MD, Christopher K.W. Lai, DM and Malcolm R. Sears, MB ChB

From the Guangzhou Institute of Respiratory Diseases (Wang, Zhong), First Affiliated Hospital of Guangzhou Medical College, Guangzhou, China; the Firestone Institute for Respiratory Health (Wang, Greene, Sears), St. Joseph's Healthcare, Hamilton, Ont.; the Department of Medicine (Wang, Greene, Sears), McMaster University, Hamilton, Ont.; the Department of Paediatrics (Wong), The Chinese University of Hong Kong, Shatin, Hong Kong, China; the Clinical and Education Centre for Asthma (Chen, Ma), Capital Institute of Paediatrics, Beijing, China; the Department of Pediatrics (Ferguson), University of British Columbia, Vancouver, BC; and the Department of Medicine and Therapeutics (Lai), The Chinese University of Hong Kong, Shatin, Hong Kong, China

Correspondence to: Malcolm R. Sears, Firestone Institute for Respiratory Health, St. Joseph's Healthcare, 50 Charlton Ave. E., Hamilton ON L8N 4A6; fax: 905 521-6132; searsm{at}mcmaster.ca

Background: Studies of the prevalence of asthma among migrating populations may help in identifying environmental risk factors.

Methods: We analyzed data from Vancouver, Canada, and from Guangzhou, Beijing and Hong Kong, China, collected during phase 3 of the International Study of Asthma and Allergies in Childhood. We subdivided the Vancouver adolescents according to whether they were Chinese immigrants to Canada, Canadian-born Chinese or Canadian-born non-Chinese. We compared the prevalence of asthma and wheezing among Chinese adolescents born in Canada, Chinese adolescents who had immigrated to Canada and Chinese adolescents living in China.

Results: Of 7794 Chinese adolescents who met the inclusion criteria, 3058 were from Guangzhou, 2824 were from Beijing, and 1912 were from Hong Kong. Of 2235 adolescents in Vancouver, Canada, 475 were Chinese immigrants, 617 were Canadian-born Chinese, and 1143 were Canadian-born non-Chinese. The prevalence of current wheezing among boys ranged from 5.9% in Guangzhou to 11.2% in Canadian-born Chinese adolescents. For girls, the range was 4.3% in Guangzhou to 9.8% in Canadian-born Chinese adolescents. The prevalence of ever having had asthma ranged from 6.6% to 16.6% for boys and from 2.9% to 15.0% for girls. Prevalence gradients persisted after adjustment for other environmental variables (odds ratios for ever having had asthma among Canadian-born Chinese compared with native Chinese in Guangzhou: 2.72 [95% confidence interval 1.75–4.23] for boys and 5.50 [95% confidence interval 3.21–9.44] for girls; p < 0.001 for both). Among Chinese adolescents living in Vancouver, the prevalence of ever wheezing increased with duration of residence, from 14.5% among those living in Canada for less than 7 years to 20.9% among those living their entire life in Canada. The same pattern was observed for the prevalence of ever having had asthma, from 7.7% to 15.9%.

Interpretation: Asthma symptoms in Chinese adolescents were lowest among residents of mainland China, were greater for those in Hong Kong and those who had immigrated to Canada, and were highest among those born in Canada. These findings suggest that environmental factors and duration of exposure influence asthma prevalence.




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Paracetamol and suppressing fever are not mentioned by the authors.
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CMAJ, 12 Dec 2008 [Full text]