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Association between smoking and genital warts: longitudinal analysis
  1. Bo Terning Hansen1,
  2. Maria Hagerup-Jenssen1,
  3. Susanne Krüger Kjær2,3,
  4. Christian Munk2,
  5. Laufey Tryggvadottir4,
  6. Pär Sparén5,
  7. Kai-Li Liaw6,
  8. Mari Nygård1
  1. 1Department of Screening-based Research, Cancer Registry of Norway, Oslo, Norway
  2. 2Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark
  3. 3Department of Obstetrics and Gynaecology, Rigshospitalet, University of Copenhagen, Denmark
  4. 4Icelandic Cancer Society, Reykjavik, Iceland
  5. 5Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm, Sweden
  6. 6Merck Research Laboratories, Merck & Co, Inc, Upper Gwynedd, Pennsylvania, USA
  1. Correspondence to Dr Bo Terning Hansen, Cancer Registry of Norway, PO Box 5313 Majorstuen, N-0304 Oslo, Norway; bo.terning.hansen{at}


Objectives To assess the association between smoking and the reported clinical diagnosis of genital warts.

Methods A sample of 58 094 women (aged 18–45) randomly drawn from the general female population of Denmark, Iceland, Norway and Sweden answered a questionnaire on lifestyle and health. Longitudinal data were reconstructed based on self report of age-specific events. In a Cox regression model, women who reported having been clinically diagnosed with genital warts were followed up until the age at first diagnosis, while women who reported never having been diagnosed with genital warts were censored at the age of interview. Age-specific smoking doses and ages at onset of smoking, sexual intercourse, condom use, hormonal contraceptive use, first pregnancy and alcohol drinking were included in the model as time-dependent covariates. The model also included lifetime number of coital partners and country of origin as fixed covariates.

Results Ever-smokers reported a lower age at first intercourse and more coital partners than never-smokers. The adjusted model showed that sexual behaviour strongly influenced the risk of being diagnosed with genital warts, and that smokers in addition had an increased risk compared with non-smokers (adjusted HR=1.27, 95% CI 1.17 to 1.37). There was also a modest additional dose–response effect of smoking, with smokers experiencing a 0.6% increased risk of being diagnosed with genital warts for each additional cigarette smoked daily (adjusted HR=1.006, 95% CI 1.001 to 1.012).

Conclusions Smokers experienced a moderately increased risk of being diagnosed with genital warts. This finding could be explained by the immunosuppressive effects of nicotine, or by confounding not accounted for in the adjusted model.

  • Condyloma acuminata
  • epidemiology
  • human papillomavirus
  • HPV
  • STI
  • risk factors
  • STD

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  • Funding Merck & Co Inc (grant number: EPO 8014.016).

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the national data protection boards and ethics committees in Denmark, Iceland, Norway and Sweden.

  • Provenance and peer review Not commissioned; externally peer reviewed.