Associated Factors and Comorbidities of Airflow Limitation in Subjects Undergoing Comprehensive Health Examination in Japan - Survey of Chronic Obstructive Pulmonary Disease Patients Epidemiology in Japan (SCOPE- J).

PURPOSE: To identify associated factors of having at least one of the airflow limitation, chronic cough/phlegm, and currently treated respiratory diseases in health examinees, and to describe the characteristics of each subgroup classified by comorbidities.

SUBJECTS AND

METHODS

This was an observational cross-sectional survey carried out in multiple regions of Japan. Subjects aged 40 years older, undergoing comprehensive health examination, were recruited. Airflow limitation was defined as having forced expiratory volume in 1 s/forced vital capacity lower than 70%. Associated factors of having at least one of the airflow limitation, chronic cough/phlegm, and currently treated respiratory diseases were examined by logistic regression analysis. Subgroup classification by comorbidity patterns was conducted by hierarchical cluster analysis.

RESULTS

In a total of 22,293 subjects, 1520 (6.8%) had at least one of the airflow limitation, chronic cough/phlegm, and currently treated respiratory diseases. With this objective variable, the following explanatory variables were significantly associated: older age, higher total score in the chronic obstructive pulmonary disease assessment test (CAT) and coexistence of lung cancer (common in ever-smokers and never-smokers), higher pack-years, lower body mass index, higher C-reactive protein, without coexistence of diabetes mellitus (specific in ever-smokers), male sex, coexistence of anxiety, and sleep disorder (specific in never-smokers). Among the 1520 subjects, 1512 subjects with smoking history data were classified by comorbidity patterns into subgroups of "no comorbidities," "mixed comorbidities," "inflammatory comorbidities," "overweight," "underweight," and "chronic kidney disease." "Inflammatory comorbidities" were specific in ever-smokers, and "underweight" was specific in never-smokers.

CONCLUSION

Several factors were identified as associated factors of having at least one of airflow limitation, chronic cough/phlegm, and currently treated respiratory diseases and they were different between ever-smokers and never-smokers. Different comorbidity patterns were observed by smoking history. These findings could provide information to assist the management of subjects with COPD or at risk for COPD in the general population.