Etiology of asthma: a continuing review (8071 cases seen from 1970--1980)

8071 cases of asthma seen during the years 1970--1980 were reviewed with regard to dominant causes of the disease in various age groups; findings were compared with a similar survey of 11,551 cases of asthma seen during the period 1958--1968. Patients were divided into two main groups--extrinsic, with dominant causes such as pollen, house dust mites, epidermals, foods, fungal spores etc. and intrinsic or cryptogenic where such allergic causes could not be incriminated. Findings confirmed those of the 1958--1968 survey with a high incidence of the cryptogenic type of disease in infants and small children and also older adults and a very high incidence of the extrinsic or allergic type of disease occurring in younger adults, particularly in the 15--29 year old age group. This latter survey also showed an increase over-all in the extrinsic type of disease (6.8%), particularly in older children with house dust and house dust mite sensitivities. It is postulated that these increases in the extrinsic type of disease may have resulted from additional methods of investigation such as RAST testing in patients who may previously have been classified as suffering from the cryptogenic type of disease without obvious allergic causes. These findings underline the need for a thorough allergic investigation of all asthmatics and the very high incidence of the extrinsic or allergic type of disease seen in young adults also poses the possibility that the high death rates seen from time to time in this group could perhaps be related to massive allergic, perhaps aerobiological, insults.