Table S1.

Summary of key study design information from cohort studies detailing COPD exacerbation rates in Japan^1–9

Study	Study design	Study center(s), recruitment period	Inclusion criteria	Definitions of COPD exacerbation
Kyoto cohort (Takahashi et al, 2012)1	Prospective cohort study	• Kyoto University Hospital • September 2006–August 2008	• Male patients with COPD • No exacerbation history criteria	Prospectively identified using diary cards, based on an increase in any two major symptoms (dyspnea, sputum purulence, and sputum quantity) or an increase in one major and one minor symptom (wheeze, sore throat, cough, and nasal congestion/discharge) for at least 2 consecutive days
Nippon cohort (Motegi et al, 2013)2	Prospective cohort study	• Nippon Medical School Respiratory Care Clinic • April–October 2007	• Patients with COPD (GOLD) • ≥40 years of age • Current or ex-smokers (≥20 pack-years) • No exacerbation history criteria	Onset or worsening of more than two symptoms (dyspnea, sputum purulence or volume, cough, or wheeze) for more than 2 consecutive days
Kitano cohort (Takemura et al, 2013)3	Prospective, pre–post, nonequivalent group study	• Kitano Hospital Medical Research Institute • November 2006–December 2010	• Patients with COPD (GOLD) • Current or ex-smokers (≥10 pack-years) • No change in medication for 3 months before study • No exacerbation history criteria	Symptomatic deterioration (dyspnea, cough, sputum purulence/volume, or wheeze) that required treatment with oral corticosteroids and/or antibiotics or hospitalization
Hokkaido cohort (Suzuki et al, 2014)4	Prospective, 5-year follow-up, observational study	• Hokkaido University Hospital • May 2003–May 2005	• Patients with COPD (GOLD) • ≥40 years of age • Current or ex-smokers (≥10 pack-years) • No exacerbation 1 month prior to study	Symptom definition: worsening or new onset of either two major symptoms or one major and one minor symptom
Saitama cohort (Kurashima et al, 2015)5	Observational study conducted to evaluate airway structure and exacerbation	• Saitama Cardiovascular and Respiratory Center • March–October 2013	• Male patients with COPD • No exacerbation history criteria	Respiratory exacerbations requiring treatment with antibiotics and/or steroid
CAP study (Matsunaga et al, 2015)6	Cross-sectional study	• Multicenter study in 15 primary or secondary care facilities in Japan	• Clinical diagnosis of COPD • 40–95 years of age • No exacerbation in the 4 weeks prior to the survey	An acute event characterized by a worsening of respiratory symptoms that was beyond normal day-to-day variations and led to a change in medication (identified using medical records)
Kurume cohort (Natori et al, 2016)7	A 52-week prospective observational study	• Kurume University and Chikugo City Hospital	• Patients with COPD (GOLD) • No exacerbation 4 weeks prior to study entry	Increased cough and sputum production, a change in sputum color, and worsening of dyspnea from a stable state and beyond normal day-to-day variations
Keio cohort (Sato et al, 2016)8	Prospective observational cohort study	• Keio University and affiliated Hospitals • April 2010–December 2012	• Patients with COPD (spirometry) • No exacerbation for ≥1 month prior to enrollment	Moderate COPD: requirement for treatment with systemic corticosteroids/antibiotics/both. Severe COPD: requiring hospitalization and emergency admission for >24 hours
Chiba cohort (Takayanagi et al, 2017)9	Prospective, 2-year, observational study	• Chiba University Hospital • May 2012–July 2014	• Patients with COPD (ATS/ERS) • Current or ex-smokers • No exacerbation history criteria	Deterioration of COPD that requires antibiotics and/or systemic steroid use

Note: All data reported as mean±SD unless otherwise stated.

Abbreviations: ATS/ERS, American Thoracic Society/European Respiratory Society recommendations; GOLD, Global initiative for chronic Obstructive Lung Disease.