Prevalence and predictors of atopy among young Danish adults

Background The prevalence of atopic diseases is increasing in western countries, and environmental exposures in childhood may influence development of atopic sensitization. Objective To investigate the prevalence and predictors of atopy among young Danish adults. Methods Of 940 invited subjects, aged 19-29 years, complete data were obtained from 525 (56%) subjects. All completed a questionnaire concerning asthma, rhinitis, preschool nursery care, smoking habits, family size, education and employment. A skin prick test was performed, and pulmonary function was measured using standard techniques. Atopy was defined as a positive skin prick test. Results The frequency of atopy was 32% (males 43% vs. females 23%, P < 0.001). We found a positive association between atopy and atopic dermatitis (P < 0.05), rhinitis (P < 0.001), itching when eating nuts (P < 0.001) and cur-rent asthma (P < 0.001). There was an inverse relation between atopy and having furred pets in childhood (P < 0,05), passive smoking in childhood (P < 0.01) and current passive smoking (P < 0.05). An increasing number of siblings was inversely related to atopy to grass (P < 0.05); however, only an increasing number of older siblings seemed to protect from atopy to grass (P < 0.05). Subjects who had never attended a day-care centre had significantly more atopy to grass (P < 0.05). No significant association was found between atopy and airway infections requiring hospitalization before the age of 5 years, or between atopy and bedroom sharing in childhood. Conclusion Atopy is common among young Danish adults, especially in males. Participants were less likely to be atopic, especially to grass allergen, if they came from large families, had kept fur-red pets as children, and had been exposed to tobacco smoke.