Sensitization to airborne allergens among adults and its impact on allergic symptoms: a population survey in northern Vietnam.

BACKGROUND: The knowledge about allergic sensitization and its relationship with clinical symptoms and diseases among adults in South-East Asia is poor. The aim of this study was to investigate the prevalence and pattern of allergic sensitization and the association with asthma and allergic rhinitis in adults in urban and rural Vietnam. METHODS: Among 5,782 responders to a questionnaire survey in northern Vietnam, a random sample was invited to a clinical follow-up and 684 (46%) participated. The methods included a structured interview using a modified GA2LEN study questionnaire on symptoms and possible determinants for diseases. Skin prick test (SPT) with ten common airborne indoor and outdoor allergens, lung function test, and methacholine test was performed among subjects ≤60 years of age. RESULTS: In total, one third of subjects had a positive SPT reaction to at least one allergen, 36.9% of men and 31.0% of women (n.s.). The most common sensitizer was the storage mite B. tropicalis (men 27.7%; women 18.7%) followed by house dust mite D. pteronyssinus (men 16.5%; women 10.6%), and D. farinae (men 15.3%; women 6.3%), and cockroach (men 16.5%; women 10.2%). Sensitization to all major allergens were significantly more common among men and among subjects ≤45 years compared with women and subjects >45 years, respectively. The prevalence of sensitization to animals, pollen and molds were low. The majority of cockroach-sensitized subjects were also sensitized to mites. Sensitization to any allergen and all major allergens were significantly associated with rhinitis, but not with asthma. However, bronchial hyper-reactivity was significantly associated with increasing number of positive SPTs (p = 0.047). CONCLUSIONS: Among adults in northern Vietnam sensitization to mite and cockroach most common in both rural and urban areas. The dominant sensitizer was the storage mite B. tropicalis, which should be included in future studies and also in clinical practice, owing to its association with clinical symptoms. As in the Western world allergic sensitization was associated with rhinitis and bronchial hyper-reactivity. The lack of association with asthma in South-East Asia needs to be studied further.

Increase in asthma and a high prevalence of bronchitis: results from a population study among adults in urban and rural Vietnam.

BACKGROUND: While a large amount of data about the epidemiology of asthma, COPD, chronic bronchitis and respiratory symptoms are available from developed countries, the information about these diseases in developing countries in south-east Asia are scarce. AIM: Assess the prevalence of respiratory diseases and symptoms and their relation with demographic data including smoking habits among adults in rural and urban Vietnam. METHODS: A random sample of subjects aged 21-70 years were invited; 3008 subjects living in an inner city area of Hanoi and 4000 in a rural area of Bavi in northern Vietnam. An internationally used questionnaire was delivered by field workers to the study subjects. The questionnaire was completed by the subjects, or when necessary, by the field workers after reading the questions for the study participants. RESULTS: The response rate was 92% in Bavi and 70% in Hanoi. Of men in Bavi 67.8% (Hanoi 49.7%; p < 0.001) were smokers, while of women 4.2% were smokers in Hanoi (Bavi 1.2%; p < 0.001). The prevalence of ever asthma was in Hanoi 5.6% (Bavi 3.9%; p = 0.003) with no major gender difference. The most common symptom was longstanding cough (Hanoi 18.1%, Bavi 12.0%; p < 0.001) followed by sputum production, while the prevalence of symptoms common in asthma was considerably lower. Although the large difference in smoking habits, respiratory symptoms tended to be only slightly more common in men than women. Family history of asthma and chronic bronchitis, respectively, were strongly associated with both diseases. CONCLUSIONS: The prevalence of asthma in adults may have increased in both urban and rural Vietnam, as the few previous estimates have found 2% of adults having asthma. Half of men in Hanoi and two-thirds in Bavi were smokers versus a few percent of women in both areas. Bronchitic symptoms were common in both men and women.

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

BACKGROUND: Little is known about prevalence and risk factors of allergic rhinitis and chronic nasal symptoms among adults in Vietnam. We aimed to estimate the prevalence, risk factor patterns and co-morbidities of allergic rhinitis and chronic nasal symptoms in one urban and one rural area in northern Vietnam. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.