THE RELATIONSHIP BETWEEN UPPER RESPIRATORY-INFECTIONS AND HOSPITAL ADMISSIONS FOR ASTHMA - A TIME-TREND ANALYSIS

We have shown that viruses are associated with 80 to 85% of asthma exa cerbations in school-age children in the community. We hypothesize tha t viral infections are also associated with severe attacks of asthma p recipitating hospital admissions. To investigate this, we conducted a time-trend analysis, comparing the seasonal patterns of respiratory in fections and hospital admissions for asthma in adults and children. Du ring a 1-yr study in the Southampton area of the United Kingdom, 108 s chool-age children monitored upper and lower respiratory symptoms and took peak expiratory flow rate (PEFR) recordings. from children report ing a symptomatic episode or a decrease in PEFR, samples were taken fo r detection of viruses and atypical bacteria. A total of 232 respirato ry viruses and four atypical bacteria were detected. The half-monthly rates of upper respiratory infection were compared with the half-month ly rates for hospital admissions for asthma (International Classificat ion of Diseases [ICD] code 493) for the same time period for the hospi tals serving the areas from which the cohort of schoolchildren was dra wn. The relationships of upper respiratory infections and hospital adm issions for asthma with school attendance were studied. Strong correla tions were found between the seasonal patterns of upper respiratory in fections and hospital admissions for asthma (r = 0.72; p < 0.0001). Th is relationship was stronger for pediatric (r = 0.68; p < 0.0001) than for adult admissions (r = 0.53; p < 0.01). Upper respiratory infectio ns and admissions for asthma were more frequent during periods of scho ol attendance (87% of pediatric and 84% of total admissions), than dur ing school holiday periods (p < 0.001). These relationships remained s ignificant when allowance was made for linear trend and seasonal varia tion using multiple regression analysis (p < 0.01). Not surprisingly, school attendance, because it is a major factor in respiratory virus t ransmission, was found to be a major confounding variable in children. This study demonstrates that upper respiratory viral infections are s trongly associated in time with hospital admissions for asthma in chil dren and adults. Rhinoviruses were the major pathogen implicated, and the majority of viral infections and asthma admissions occurred during school attendance.