title: The risk of asthma in patients with ankylosing spondylitis: a population-based cohort study.
abstract: BACKGROUND
  The relationship between asthma and ankylosing spondylitis (AS) is controversial. We examined the risk of asthma among AS patients in a nationwide population.
  
  
  METHODS
  We conducted a retrospective cohort study using data from the National Health Insurance (NHI) system of Taiwan. The cohort included 5,974 patients newly diagnosed with AS from 2000 to 2010. The date of diagnosis was defined as the index date. A 4-fold of general population without AS was randomly selected frequency matched by age, gender and the index year. The occurrence and hazard ratio (HR) of asthma were estimated by the end of 2011.
  
  
  RESULTS
  The overall incidence of asthma was 1.74 folds greater in the AS cohort than in the non-AS cohort (8.26 versus 4.74 per 1000 person-years) with a multivariable Cox method measured adjusted HR of 1.54 (95% confidence interval (CI), 1.34-1.76). The adjusted HR of asthma associated with AS was higher in women (1.59; 95% CI, 1.33-1.90), those aged 50-64 years (1.66; 95% CI, 1.31-2.09), or those without comorbidities (1.82; 95% CI, 1.54-2.13).
  
  
  CONCLUSIONS
  Patients with AS are at a higher risk of developing asthma than the general population, regardless of gender and age. The pathophysiology needs further investigation.
authors: Graduate Institute of Clinical Medicine Science, College of Medicine, China Medical University, Taichung, Taiwan; Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, China Medical University Hospital, China Medical University, Taichung, Taiwan.
authors: Te-Chun
authors: TC
authors: Shen
authors: Management Office for Health Data, China Medical University Hospital, China Medical University, Taichung, Taiwan.
authors: Cheng-Li
authors: CL
authors: Lin
authors: Division of Nephrology, Department of Pediatrics, China Medical University Hospital, China Medical University, Taichung, Taiwan.
authors: Chang-Ching
authors: CC
authors: Wei
authors: Graduate Institute of Clinical Medicine Science, College of Medicine, China Medical University, Taichung, Taiwan; Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, China Medical University Hospital, China Medical University, Taichung, Taiwan.
authors: Chia-Hung
authors: CH
authors: Chen
authors: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, China Medical University Hospital, China Medical University, Taichung, Taiwan.
authors: Chih-Yen
authors: CY
authors: Tu
authors: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, China Medical University Hospital, China Medical University, Taichung, Taiwan.
authors: Te-Chun
authors: TC
authors: Hsia
authors: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, China Medical University Hospital, China Medical University, Taichung, Taiwan.
authors: Chuen-Ming
authors: CM
authors: Shih
authors: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, China Medical University Hospital, China Medical University, Taichung, Taiwan.
authors: Wu-Huei
authors: WH
authors: Hsu
authors: Graduate Institute of Clinical Medicine Science, College of Medicine, China Medical University, Taichung, Taiwan; Management Office for Health Data, China Medical University Hospital, China Medical University, Taichung, Taiwan.
authors: Fung-Chang
authors: FC
authors: Sung
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D001249:Asthma / Q000453:epidemiology* / Q000209:etiology*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D018570:Risk Assessment; D017678:Sex Distribution; D013167:Spondylitis, Ankylosing / Q000150:complications* / Q000453:epidemiology; D013624:Taiwan / Q000453:epidemiology; D055815:Young Adult