title: Associations Between Sildenafil Use and Changes in Days of Hospitalization in a Population With Pulmonary Arterial Hypertension Associated With Connective Tissue Disease.
abstract: OBJECTIVE
  Pulmonary arterial hypertension (PAH) can be a complication in patients with connective tissue disease (CTD). Although the phosphodiesterase-5 inhibitor sildenafil shows evidence of efficacy and tolerability among patients with PAH associated with CTD in clinical trials, no studies have examined the association between its use and health care resource utilization in clinical practice. The objective of this study was to assess the associations between the use of sildenafil and health care resource utilization, specifically days of hospitalization, in a population with PAH associated with CTD.
  
  
  METHODS
  A retrospective, matched, case-control analysis was conducted using data from a commercial claims database. Patients with a claim dated between 2003 and 2009 were selected. Cases and controls were matched on age, sex, and baseline total days of hospitalization. A longitudinal, zero-inflated, negative binomial model was used for analyzing the data after control for age, sex, region, Charlson comorbidity score, and use of PAH-specific medication other than sildenafil.
  
  
  RESULTS
  A total of 420 individuals, 210 cases and 210 controls, were included in the sample. The sample was 85.71% women, and the mean age was 57.6 years. Estimates for variances of an intercept random effect (5.08 × 10(-13)) and for a time-variable random effect (2.84 × 10(-16)) were both essentially zero. Thus a zero-inflated negative binomial model without random effects was used. When individuals were not using sildenafil, each 1-month interval was associated with a 2.8% increase in the mean number of days of hospitalization. In contrast, when individuals were using sildenafil, each 1-month interval was associated with a decrease of 3.3% in days of hospitalization.
  
  
  CONCLUSIONS
  In this data analysis of the association between sildenafil use and days of hospitalization among individuals with PAH associated with CTD in a large-scale population, sildenafil use in the treatment of PAH associated with CTD was associated with reduced days of hospitalization during the year after the initiation of treatment.
authors.affiliation: Regenstrief Center for Healthcare Engineering and the Center for Health Outcomes Research and Policy, College of Pharmacy, Purdue University, West Lafayette, Indiana.
authors.forename: Xiaoqin
authors.initials: X
authors.lastname: Yang
authors.affiliation: Outcomes and Evidence Group, Global Health and Value Platform, Pfizer Inc, New York, New York.
authors.forename: Kafi N
authors.initials: KN
authors.lastname: Sanders
authors.affiliation: Global Innovative Pharma - Statistics, Pfizer Inc, New York, New York.
authors.forename: Jack
authors.initials: J
authors.lastname: Mardekian
authors.affiliation: Outcomes and Evidence Group, Global Health and Value Platform, Pfizer Inc, New York, New York.
authors.forename: Marko A
authors.initials: MA
authors.lastname: Mychaskiw
authors.affiliation: Regenstrief Center for Healthcare Engineering and the Center for Health Outcomes Research and Policy, College of Pharmacy, Purdue University, West Lafayette, Indiana. Electronic address: jt3@purdue.edu.
authors.forename: Joseph
authors.initials: J
authors.lastname: Thomas
mesh_terms: D000328:Adult; D000368:Aged; D003240:Connective Tissue Diseases / Q000150:complications*; D005260:Female; D006295:Health Resources / Q000706:statistics & numerical data; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D006976:Hypertension, Pulmonary / Q000188:drug therapy* / Q000209:etiology; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D058986:Phosphodiesterase 5 Inhibitors / Q000627:therapeutic use*; D012189:Retrospective Studies; D000068677:Sildenafil Citrate / Q000627:therapeutic use*; D014481:United States; D014665:Vasodilator Agents / Q000627:therapeutic use*
chemical_list: D058986:Phosphodiesterase 5 Inhibitors; D014665:Vasodilator Agents; D000068677:Sildenafil Citrate
keywords: connective tissue disease; days of hospitalization; health care utilization; pulmonary hypertension