Allergic rhinitis in northern vietnam: increased risk of urban living according to a large population survey

A cross-sectional questionnaire survey was conducted from August 2007 to January 2008 in urban Hoankiem and rural Bavi in Hanoi among adults aged 21-70 years. Of 7008 randomly selected subjects, 91.7% participated in Bavi and 70.3% in Hoankiem.Allergic rhinitis ever or chronic nasal symptoms were reported by 50.2%. The prevalence of allergic rhinitis ever was considerably higher in Hoankiem compared to Bavi, 29.6% vs 10.0% (p < 0.001). Allergic rhinitis ever and chronic nasal symptoms were both significantly associated with asthma and respiratory symptoms, respectively (p < 0.001). Exposure to gas, dust or fumes at work was significantly associated with allergic rhinitis ever, OR 1.57 (95% CI 1.34 - 1.84), nasal blocking, OR 1.90 (95% CI 1.68 - 2.15) and runny nose, OR 1.32 (95% CI 1.17 - 1.49), while somewhat surprisingly no association with smoking was found. Female sex was a significant risk factor for both nasal blocking and runny nose.Allergic rhinitis ever was considerably more common in the urban area. Nasal blocking and runny nose was each reported by about one third of the studied sample with no major urban-rural difference. Further, exposure to air pollution at work was significantly associated with allergic rhinitis ever, nasal blocking and runny nose.The prevalence of allergic diseases including allergic rhinitis has been increasing all over the world since about the middle of the past century [1]. The prevalence of allergic rhinitis differs between countries and even between areas within countries [2]. These differences may partly be due to different definitions and methods used [3]. Recent epidemiological studies suggest that urban living and exposure to air pollution at home and at work place are risk factors for allergic rhinitis [4], while rural living [5], particularly living on a farm the first year of life may have a protective effect on allergic rhinitis [6]. The most common cause of allergic rhinitis is allergic sensitization to airborne allerg