In line with the hygiene hypothesis for the development of allergic conditions, German researchers have identified an inverse association between periodontitis and respiratory allergies.

Periodontitis is a local oral infection that has systemic effects. Nele Friedrich (Ernst Moritz Arndt University, Greifswald) and colleagues proposed that, in the framework of the hygiene hypothesis, such systemic effects could protect against the development of allergic diseases.

To explore this possibility, the researchers studied a total of 2837 individuals, aged 20 to 59 years, who participated in the Study of Health in Pomerania.

Dentists assessed the dental status of each participant, measuring periodontitis by cumulative attachment loss (AL) – the distance from the cemento-enamel junction to the bottom of the periodontal pocket.

The percentage of surfaces exceeding 3 mm AL was determined in each person, and then the group was divided into quartiles according thedegree of AL, with 0%-7.7% considered healthy periodontal conditions, 7.8%-28.6% as low periodontitis, 28.7%-63.9% AL as moderate periodontitis, and >63.9% AL as severe periodontitis.

Collecting medical histories by interview, the researchers identified 326, 111, and 114 individuals as suffering from hayfever, house dust mite (HDM) allergy, and asthma, respectively.

After adjustment for confounding factors, inverse associations were found between AL and hayfever and HDM allergy.

For hayfever, odds ratios (ORs) of 0.87, 0.80, and 0.53 were observed for low, moderate, and severe AL compared with healthy periodontal status, respectively, representing a trend towards decreasing risk with increasing severity of periodontitis.

Similarly, a trend towards decreasing risk of house dust mite allergy was seen, with ORs of 0.80, 0.64, and 0.39, respectively with each increase in severity of periodontitis.

A slight inverse association was also seen for periodontitis and asthma, with ORs of 1.10, 0.96, and 0.48, for low, moderate, and severe AL relative to healthy periodontal status, respectively.

"In conclusion, there is an inverse association between periodontitis and respiratory allergies," Friedrich and team conclude in the journal Clinical and Experimental Allergy.

They add: "The present findings might support the hygiene hypothesis."

Free abstract