External companies administered the questionnaires with cover letters and prepaid envelopes for returning the completed questionnaires, as well as the computerisation of collected data. Non-responders received three reminders. The invited individuals were also given the option to respond over the internet.
The questionnaire included three parts. The first part was a modified version [29 (link)] of the Swedish OLIN study questionnaire [23 (link)] that has been used in several studies in northern Europe [24 -27 (link)] and contained questions about asthma, rhinitis, chronic bronchitis/COPD/emphysema, respiratory symptoms, use of asthma medication and possible determinants of disease, such as smoking habits and family history of airway diseases. The second part included questions about occupation, airborne occupational and environmental exposures, socio-economic status and health status. The third part consisted of the Swedish version of the GA2LEN questionnaire, which added detailed questions about rhinitis and eczema.
The questionnaire included three parts. The first part was a modified version [29 (link)] of the Swedish OLIN study questionnaire [23 (link)] that has been used in several studies in northern Europe [24 -27 (link)] and contained questions about asthma, rhinitis, chronic bronchitis/COPD/emphysema, respiratory symptoms, use of asthma medication and possible determinants of disease, such as smoking habits and family history of airway diseases. The second part included questions about occupation, airborne occupational and environmental exposures, socio-economic status and health status. The third part consisted of the Swedish version of the GA2LEN questionnaire, which added detailed questions about rhinitis and eczema.
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