title: Psoriasis and Sleep Apnea: A Danish Nationwide Cohort Study.
abstract: Psoriasis and sleep apnea are associated with significant morbidity and mortality. Although both diseases have been linked with systemic inflammation, studies on their potential bidirectional association are lacking. We investigate the potential association between psoriasis and sleep apnea.
  
  
  
  All Danish citizens age 18 y or older between January 1, 1997 and December 31, 2011 (n = 5,522,190) were linked at individual level in nationwide registries. Incidence rates (IRs) per 10,000 person-years were calculated and incidence rate ratios (IRRs) adjusted for age, sex, socioeconomic status, smoking history, alcohol abuse, medication, and comorbidity were estimated by Poisson regression.
  
  
  
  There were 53,290, 6,885, 6,348, and 39,908 incident cases of mild psoriasis, severe psoriasis, psoriatic arthritis, and sleep apnea, respectively. IRRs (95% confidence interval) for sleep apnea were 1.30 (1.17-1.44), 1.65 (1.23-2.22), and 1.75 (1.35-2.26) in subjects with mild and severe psoriasis, and psoriatic arthritis, and IRRs for mild and severe psoriasis, and psoriatic arthritis in sleep apnea without continuous positive airway pressure (CPAP) therapy were 1.62 (1.41-1.86), 2.04 (1.47-2.82), and 1.94 (1.34-2.79), respectively. In patients with sleep apnea and CPAP therapy (i.e., severe sleep apnea) the IRRs were 1.82 (1.43-2.33), 3.27 (2.03-5.27), and 5.59 (3.74-8.37), respectively.
  
  
  
  Psoriasis was associated with increased risk of sleep apnea, and sleep apnea was associated with increased risk of psoriasis. The clinical significance of this bidirectional relationship warrants further study.
authors.affiliation: Department of Cardiology, Herlev and Gentofte Hospital, University of Copenhagen, DK-2900 Hellerup.|Department of Dermato-Allergology, Herlev and Gentofte Hospital, University of Copenhagen, DK-2900 Hellerup.
authors.forename: Alexander
authors.initials: A
authors.lastname: Egeberg
authors.affiliation: Department of Cardiology, Herlev and Gentofte Hospital, University of Copenhagen, DK-2900 Hellerup.
authors.forename: Usman
authors.initials: U
authors.lastname: Khalid
authors.affiliation: Department of Cardiology, Herlev and Gentofte Hospital, University of Copenhagen, DK-2900 Hellerup.
authors.forename: Gunnar Hilmar
authors.initials: GH
authors.lastname: Gislason
authors.affiliation: Unit of Dermatology and Venereology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Lotus
authors.initials: L
authors.lastname: Mallbris
authors.affiliation: Department of Dermato-Allergology, Herlev and Gentofte Hospital, University of Copenhagen, DK-2900 Hellerup.
authors.forename: Lone
authors.initials: L
authors.lastname: Skov
authors.affiliation: Department of Cardiology, Herlev and Gentofte Hospital, University of Copenhagen, DK-2900 Hellerup.
authors.forename: Peter Riis
authors.initials: PR
authors.lastname: Hansen
mesh_terms: D000328:Adult; D015331:Cohort Studies; D015897:Comorbidity; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D011565:Psoriasis / Q000453:epidemiology*; D012042:Registries; D012307:Risk Factors; D012720:Severity of Illness Index; D012891:Sleep Apnea Syndromes / Q000453:epidemiology*
keywords: epidemiology; inflammation; psoriasis; risk; sleep apnea