Study data points to periodontal disease as psoriasis risk factor

Key Points

Phoenix - Analyses of prospectively collected data from the Nurses' Health Study (NHS) suggest periodontal disease (PD) may be a risk factor for psoriasis, reported Sarah Nakib, M.D., M.P.H., at the 2011 meeting of the Society for Investigative Dermatology.

Dr. Nakib is a resident, department of dermatology and internal medicine, University of Minnesota, Minneapolis. She worked on the study under the mentorship of Abrar A. Qureshi, M.D., M.P.H., Channing Laboratory, Harvard Medical School, through a Medical Dermatology Society Mentorship award.

Dr. Nakib, Dr. Qureshi, Jiali Han, Ph.D., and members of their lab investigated an association between PD and the development of psoriasis using self-reported dental history information collected in questionnaires administered to participants in the longitudinal NHS between 1992 and 2000. Self-reported data on periodontal bone loss available from more than 60,000 women was used as a proxy for diagnosis of PD and represented the primary exposure analyzed as a risk factor for psoriasis. In addition, associations were examined between incident psoriasis and self-reported history of periodontal surgery in the past two years, root canal work, tooth loss in the past two years and number of natural teeth.

In Cox proportional hazards analyses adjusting for age, smoking, body mass index, alcohol intake and physical activity, women reporting either mild periodontal bone loss or moderate-to-severe periodontal bone loss were at significantly increased risk of psoriasis compared with a reference group having no history of periodontal bone loss (relative risk 1.36 and 1.54, respectively). A history of periodontal surgery and history of three or more root canals were also significant predictors of incident psoriasis risk (relative risk 1.29 and 1.24, respectively). No significant associations were found between risk for development of psoriasis and number of natural teeth or history of tooth loss.

"The findings from our study are consistent with other published literature that provides evidence of an association between PD and psoriasis. However, this is the first large study using longitudinally collected data to evaluate PD as a risk factor for psoriasis," Dr. Nakib says. "Despite its strengths, our study has some limitations, and further research on this topic is needed. Nevertheless, based on the available evidence, we believe it would be reasonable for providers to address modifiable risk factors for maintaining dental health in their patients at risk for psoriasis."

Study limitations

Discussing the limitations of the study, Dr. Nakib says the NHS participants represent a somewhat homogeneous population of predominantly white, well-educated women. Therefore, the results cannot be generalized to men, other racial groups or more indigent populations. In addition, because the study has an observational design, there is the possibility for confounding of the results from unmeasured factors.

"While the dental history data are based on self-reports, in a previous study of health professionals, self-reported periodontal bone loss was validated as a good marker for PD using findings on alveolar bone loss (Joshipura KJ, Douglass CW, Garcia RI, et al. J Public Health Dent. 1996;56(4):205-212). Furthermore, the association found in our primary outcome measure was corroborated by several of our secondary analyses investigating other possible surrogates of PD," she says.

Dr. Qureshi's group is currently working to confirm self-reported psoriasis with a more detailed, validated questionnaire with good results.

"Hopefully, other investigators will evaluate these associations in other studies," Dr. Nakib says.

There is a recently published case-control study (Acta Odontol Scand. 2010 Feb 8. Epub ahead of print) that found patients with psoriasis had significantly lower radiographic bone level and significantly more missing teeth than an age- and gender-matched control population without psoriasis. In addition, there are case reports describing exacerbation of palmoplantar pustulosis, a type of psoriasis, accompanying increased periodontitis (J Periodontol. 1992;63:854-857) and regression of palmoplantar pustulosis after various treatments for periodontitis (Akazawa Hiroshi, Nishimura F, Maeda H, et al. Int J Dermatol. 2006;45(12):1420-1422; Sakiyama H, Kobayashi S, Dianzani U. J Dermatol Sci. 2008;50(3):197-207).

"PD involves infection with a range of gram-negative bacteria that invade the superficial and deep gingival tissues. It is biologically plausible that chronic low-grade periodontal inflammation may stimulate the psoriasis pathway directly or via induction of a systemic inflammatory response," Dr. Nakib says.