Article Text

The association of dental plaque with cancer mortality in Sweden. A longitudinal study
  1. Birgitta Söder1,
  2. Maha Yakob1,
  3. Jukka H Meurman2,
  4. Leif C Andersson3,
  5. Per-Östen Söder1
  1. 1Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden
  2. 2Department of Oral and Maxillofacial Diseases, Institute of Dentistry, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland
  3. 3Department of Pathology, Haartman Institute, University of Helsinki, Helsinki, Finland
  1. Correspondence to Dr Birgitta Söder; birgitta.soder{at}


Objectives To study whether the amount of dental plaque, which indicates poor oral hygiene and is potential source of oral infections, associates with premature death from cancer.

Design Prospective cohort study.

Participants 1390 randomly selected healthy young Swedes followed up from 1985 to 2009. All subjects underwent oral clinical examination and answered a questionnaire assessing background variables such as socioeconomic status and smoking.

Outcome measures Causes of death were recorded from national statistics and classified according to the WHO International Classification of Diseases. Unpaired t test, χ2 tests and multiple logistic regressions were used.

Results Of the 1390 participants, 4.2% had died during the follow-up. Women had died at a mean age of 61.0 (±2.6 SD) years and men at the age of 60.2 (±2.9 SD) years. The amount of dental plaque between those who had died versus survived was statistically significant (p<0.001). In multiple logistic regression analysis, dental plaque appeared to be a significant independent predictor associated with 1.79 times the OR of death (p<0.05). Age increased the risk with an OR of 1.98 (p<0.05) and gender (men) with an OR of 1.91 (p<0.05). The malignancies were more widely scattered in men, while breast cancer was the most frequent cause of death in women.

Conclusions This study hypothesis was confirmed by showing that poor oral hygiene, as reflected in the amount of dental plaque, was associated with increased cancer mortality.

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: and

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  • To cite: Söder B, Yakob M, Meurman JH, et al. The association of dental plaque with cancer mortality in Sweden. A longitudinal study. BMJ Open 2012;2:e001083. doi:10.1136/bmjopen-2012-001083

  • Contributors All authors fulfil all three of the ICMJE guidelines for authorship that are (1) substantial contributions to conception and design, acquisition of data or analysis and interpretation of data; (2) drafting the article or revising it critically for important intellectual content and (3) final approval of the version to be published. Dr BS is the corresponding author. She had full access to all data in the study and had final decision to submit the manuscript for publication.

  • Funding This study was supported by Ministry of Health and Social Affairs (grants F84/189) and Karolinska Institutet, Stockholm, Sweden, The Finnish Medical Society, Helsinki, and by grant TI020Y0003 by the Helsinki University Central Hospital, Finland.

  • Competing interests None.

  • Patient consent Obtained.

  • Ethics approval Ethics approval was provided by the Ethics Committee of the Karolinska Institute and Huddinge University Hospital, Sweden, had approved the study protocol (permit 2007/1669-31). The study is in accordance with the Declaration of Helsinki as revised in 1983.

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

  • Data sharing statement No unpublihed data are available.