Incidence of influenza-like illness, measured by a general practitioner sentinel system, is associated with day-to-day variations in respiratory health in panel studies

Abstract

During three consecutive winters beginning in 1992-1993, the association between the incidence of influenza and influenza-like illness (ILI), measured by a general practitioner sentinel system, and respiratory health was investigated in an air pollution panel study. Data from 22 panels of children (7-11 years old) and adults (50-70 years old) in the Netherlands were used. ILI incidence was associated with peak expiratory flow, respiratory symptoms, and bronchodilator use. Peak ILI incidence of 122 cases/10,000 subjects was associated with a decrement in peak expiratory flow of 6% and a 3- to 4.5- fold increase in symptom reporting and bronchodilator use. In panel studies, ILI incidence might be used to adjust for confounding by acute respiratory infections.