RESULTS
death, asthma, COPD, shortness of breath
EVENT, DISEASE, CHRONIC OBSTRUCTIVE PULMONARY DISEASE, COPD, ASTHMA
The difference in smoking habits, symptoms mortality, and education among the combined effects groups is shown in Table Demographic Data, Smoking Habits, and Symptom Prevalence in Relation to Combined EffectsData are presented as COPD, chronic obstructive pulmonary disease; shortness of breath defined as having shortness of breath when walking on a flat ground with own age group; IQR, interquartile range; cig., cigarette.At baseline, the most of the combined high exposure groups included more men, were older, had more current smokers, were more symptomatic, had lower education, and had higher all-cause mortality. Coexisting groups had the highest number of years in their principal occupation. The notable difference in this was the asthma alone groups, which had similar age and symptom tendencies among the different occupational exposures.Table Exposure and Diagnosis in Association to All-Cause Mortality Hazards RatiosThe models are adjusted for age, education, sex, and smoking status.No diagnosis is defined as not having asthma or COPD, and event is defined as a reported by a death certificate.Statistically significant results are bolded.The COPD, chronic obstructive pulmonary disease; CI, confidence interval.Combined effects all-cause mortality survival functions.In the separate effects model, high exposure group had a significant HR for all-cause mortality varying from 1.34 (1.11–1.62) to 1.38 (1.14–1.66) depending on the model. Only coexisting asthma and COPD had a significant HR (1.58; 95% confidence interval, 1.10–2.27).In the combined model, only coexisting asthma and COPD showed significant results out of the disease groups, combined with either intermediate or high exposure, having HRs of 2.20 (1.18–4.09) and 1.94 (1.10–3.42), respectively.For further analysis, we also computed a competing risks model for all respiratory causes using both the underlying and contributing causes of death. The results can be seen in Table Exposure and Diagnose in Association to All-Cause Mortality Hazards RatiosThe models are adjusted for age, education, sex, and smoking status.No diagnosis is defined as not having asthma or COPD, and event is defined as a reported by a death certificate.Statistically significant results are bolded.COPD, chronic obstructive pulmonary disease: coexisting, self-reported physician made diagnosis of both asthma and COPD; CI, confidence interval.These models were computed with the Fine-Gray model for competing risks. The results for the respiratory-related mortality are similar to all-cause mortality, although exposure alone does not give a significant sub-hazard. The result for coexisting asthma and COPD is significant both in the separate model as well as the combined effects model.The Kaplan-Meier survival model was used to compare the restricted mean survival times for participants who were at least 50 years old in 1996, using the combined effects variable. The results of this comparison can be seen in Supplementary Table 5, Survival curves in participants restricted to only those of 50 years and older.