Prevalence of, and risk factors for, adult onset wheeze : a thirty year follow-up study
A thirty year follow-up survey was carried out to determine the prevalence of adult onset wheeze in a randomly selected community cohort of 2,056 adults who had had no childhood respiratory symptoms when they were originally studied in 1964. New onset wheezing symptoms developed at a steady rate of 0.5 per 100 person years between age 15 and 14; 11.5% of subjects reported having had an attack of wheezing for the first time during this period of their lives. Adult onset disease accounted for a greater proportion (62.9%) of current wheezing in middle age than child onset disease (37.1%). The risk of adult onset wheeze among all cases who had ever wheezed since age 15 increased with low socioeconomic status, current smoking, positive atopic status and positive family history of atopic disease. Gender was not related to risk of wheeze. Vitamin C and E consumption were inversely related to the risk of current wheeze (i.e. wheeze in the previous 12 months); analyses stratified by social class and smoking habit suggested that these inverse associations were stronger in the manual compared to the nonmanual class, and among smokers compared to nonsmokers. Childhood factors, including father's social class, sibship structure and common childhood infections were not related to adult onset wheeze. The pattern of significant independent risk factors differed between three distinct subgroups of cases who reported doctor-diagnosed asthma (n=24), chronic cough and phlegm (n=31) or other wheeze (n=47). Manual social class was associated with cough and phlegm and other wheeze. Smoking was only related to cough and phlegm. Atopy was associated with doctor-diagnosed asthma and with cough and phlegm. Family history of atopic disease was related to all subgroups, suggesting that despite apparent heterogeneity in diagnostic labelling, concurrent symptoms and other risk factors, the different forms of adult onset wheeze may share a common allergic basis.