title: Identification of five clusters of comorbidities in a longitudinal Japanese chronic obstructive pulmonary disease cohort.
abstract: Patients with chronic obstructive pulmonary disease (COPD) frequently suffer from various comorbidities. Recently, cluster analysis has been proposed to examine the phenotypic heterogeneity in COPD. In order to comprehensively understand the comorbidities of COPD in Japan, we conducted multicenter, longitudinal cohort study, called the Keio COPD Comorbidity Research (K-CCR). In this cohort, comorbid diagnoses were established by both objective examination and review of clinical records, in addition to self-report. We aimed to investigate the clustering of nineteen clinically relevant comorbidities and the meaningful outcomes of the clusters over a two-year follow-up period.
  
  
  
  The present study analyzed data from COPD patients whose data of comorbidities were completed (n = 311). Cluster analysis was performed using Ward's minimum-variance method.
  
  
  
  Five comorbidity clusters were identified: less comorbidity; malignancy; metabolic and cardiovascular; gastroesophageal reflux disease (GERD) and psychological; and underweight and anemic. FEV1 did not differ among the clusters. GERD and psychological cluster had worse COPD assessment test (CAT) and Saint George's respiratory questionnaire (SGRQ) at baseline compared to the other clusters (CAT: p = 0.0003 and SGRQ: p = 0.00046). The rate of change in these scores did not differ within 2 years. The underweight and anemic cluster included subjects with lower baseline ratio of predicted diffusing capacity (DLco/VA) compared to the malignancy cluster (p = 0.036).
  
  
  
  Five clusters of comorbidities were identified in Japanese COPD patients. The clinical characteristics and health-related quality of life were different among these clusters during a follow-up of two years.
authors: Division of Pulmonary Medicine, Department of Medicine, Keio University School of Medicine, Japan. Electronic address: bachibachi472000@live.jp.
authors: Shotaro
authors: S
authors: Chubachi
authors: Division of Pulmonary Medicine, Department of Medicine, Keio University School of Medicine, Japan.
authors: Minako
authors: M
authors: Sato
authors: Division of Pulmonary Medicine, Department of Medicine, Keio University School of Medicine, Japan.
authors: Naofumi
authors: N
authors: Kameyama
authors: Division of Pulmonary Medicine, Department of Medicine, Keio University School of Medicine, Japan.
authors: Akihiro
authors: A
authors: Tsutsumi
authors: Division of Pulmonary Medicine, Department of Medicine, Keio University School of Medicine, Japan.
authors: Mamoru
authors: M
authors: Sasaki
authors: Division of Pulmonary Medicine, Department of Medicine, Keio University School of Medicine, Japan.
authors: Hiroki
authors: H
authors: Tateno
authors: Division of Pulmonary Medicine, Department of Medicine, Keio University School of Medicine, Japan; Department of Respiratory Medicine, Saitama Medical University, Japan.
authors: Hidetoshi
authors: H
authors: Nakamura
authors: Division of Pulmonary Medicine, Department of Medicine, Tokai University School of Medicine, Japan.
authors: Koichiro
authors: K
authors: Asano
authors: Division of Pulmonary Medicine, Department of Medicine, Keio University School of Medicine, Japan.
authors: Tomoko
authors: T
authors: Betsuyaku
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000740:Anemia / Q000453:epidemiology; D002318:Cardiovascular Diseases / Q000453:epidemiology; D016000:Cluster Analysis; D015331:Cohort Studies; D015897:Comorbidity / Q000639:trends*; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume / Q000502:physiology; D005764:Gastroesophageal Reflux / Q000453:epidemiology; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008137:Longitudinal Studies; D008297:Male; D009369:Neoplasms / Q000453:epidemiology; D010641:Phenotype; D011446:Prospective Studies; D011653:Pulmonary Diffusing Capacity / Q000379:methods; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000503:physiopathology*; D011788:Quality of Life; D057566:Self Report; D012907:Smoking / Q000453:epidemiology; D013851:Thinness / Q000453:epidemiology; D014057:Tomography, X-Ray Computed
keywords: Chronic obstructive pulmonary disease; Cluster analysis; Comorbidity; Phenotype; Quality of life