Testing the Relationship Between Respiratory Diseases and Viral Infections in Various Age Groups

Abstract

The objective of this project was to investigate and determine the association between hospitalizations of respiratory diseases with one another and with isolations of viral infections in five age groups. Weekly data on all hospitalizations in Ontario, Canada, from week 14 of 2001 to week 13 of 2003 were obtained for 5 age groups (under 2 years, 2 to 4 years, 5 to 15 years, 16 to 49 years and over 50 years inclusive) for respiratory diseases including, asthma, respiratory tract infection (RTI) and chronic obstructive pulmonary disease (COPD)1. Furthermore, data for viral infections including influenza virus type A and type B (Flu AB) and respiratory syncytial virus (RSV) isolations were also obtained from Health Canada for the same weekly time periods. In order to test for independence and determine a relationship, if any, between hospitalizations of respiratory diseases with one another and with isolations of viral infections, structural time series models were developed for all age groups of the respiratory diseases and explanatory variables were modeled accordingly against the hospital admission counts for the respiratory diseases. These explanatory variables include, other respiratory diseases, viral infections, and lagged values of the dependent variable. Neither FLU AB nor RSV showed a significant relationship with asthma patients of all ages. Weekly RSV peaks coincided with RTI patients under 2 years and RTI peaks in patients 5 to 15 years preceded FLU AB peaks. A relationship between all three respiratory diseases, asthma RTI and COPD, was discovered for all age groups. Peaks of asthma coincided with various transformations of RTI peaks for the five age groups and peaks of COPD coincided with both the untransformed asthma and RTI peaks in patients over 50. For all other relationships, the null hypothesis of independence was accepted. These findings suggest that there is a strong association between respiratory diseases and that children and adults with respiratory diseases respond differently to viral infections. 1 Only data for patients over 50 years was obtained for COPD.