A Systematic Review of Kissing as a Risk Factor for Oropharyngeal Gonorrhea or Chlamydia

Background Tongue kissing is a poorly studied risk factor for sexually transmitted infections (STIs). We undertook the first systematic review to assess whether kissing is a risk factor for gonorrhea or chlamydia of the oropharynx. Methods Online databases (MEDLINE, EMBASE, CINAHL, Web of Science, Cochrane) and reference lists were searched until September 30, 2022. The eligibility criteria for studies included: any peer-reviewed study design in the English language; gonorrhea or chlamydia diagnosed by nucleic acid amplification test, or an infection self-reported by a patient; tongue kissing or its equivalent measured as an exposure. Studies were appraised using a quality scoring tool and qualitatively synthesized. Results Of 8248 studies screened, 6 were eligible for review. All were conducted among men who have sex with men in Australia, including 3 prospective cohort studies, 2 cross-sectional studies, and 1 age-matched case-control study. In summary, all 5 studies examining gonorrhea found an unadjusted association between kissing and oropharyngeal gonorrhea. Two cross-sectional studies found that tongue kissing was an independent risk factor for oropharyngeal gonorrhea after adjusting for other confounders, such as participant demographic characteristics and other sexual practices. In contrast, a single eligible prospective cohort study found no association between kissing and oropharyngeal chlamydia. Conclusions This systematic review summarized the existing evidence that suggests that tongue kissing may be a risk factor for oropharyngeal gonorrhea but not chlamydia. Reinforcing the message that oropharyngeal gonorrhea could be transmitted through kissing may inform the development of novel approaches to prevent and treat gonorrhea.