Epidemiological study of the relations between asthma and occupation: pilot study of a postal questionnaire

In the context of a proposed study of asthma and occupation we have tested the response to a postal self-administered questionnaire designed to investigate respiratory symptoms compatible with a diagnosis of asthma. Thirteen hundred adults over the age of sixteen, selected by stratified random sampling, from the electoral register of three communities in East Central Scotland, were invited to complete a two page questionnaire, based on that described by Burney and Chinn (Chest Supplement 1987; 91:79s). Non-responders were sent reminders and a further questionnaire during the subsequent two months and the response rate at each stage was recorded. In total, one thousand and twenty seven people returned completed questionnaires, corresponding to seventy nine per cent of those invited. If those who had died or who had moved away were excluded from the total number invited, this would have given a response rate of nearly eighty three per cent. The prevalence of symptoms during the last year was examined within strata. Twenty two per cent reported wheezing whilst thirteen per cent reported having woken up with tightness in their chest. Ten per cent reported having an attack of shortness of breath whilst five per cent reported being woken at night by such an attack. Prevalence of these symptoms was generally greater in men than in women, and men reported shortness of breath increasingly more frequently with age. Wheeze and chest tightness were more frequently reported among smokers and residents of districts with a greater proportion of council housing. Overall six per cent reported ever having had asthma. Residents of one town reported ever having had asthma more frequently (8.3%) than the other two locations (4.8% and 5.7%).Unidentifiable information about recent consultation rates for respiratory illnesses was provided by GPs on a small sample of responders. The consultation rate of 33% was not very different from the rate (38%) of a random selection of patients from the same practices. In conclusion, this postal survey has provided data on respiratory symptoms for use in an epidemiological study, from about eighty percent of those individuals to whom questionnaires were sent.This work is supported by the Asthma Research Council.