Incidence of Nongonococcal Urethritis in Men Who Have Sex With Women and Associated Risk Factors

Abstract

BACKGROUND: Incidence and risk factors for nongonococcal urethritis (NGU) remain poorly defined. We conducted a cohort study to estimate the incidence of NGU and identify risk factors in men who have sex with women. METHODS: We enrolled cisgender male STD clinic attendees age ≥16 who reported exclusively female partners. At enrollment and six monthly follow-up visits, men underwent a clinical exam, provided urethral swab and urine specimens, completed a sexual behavior survey and bi-weekly diaries, and were tested for Chlamydia trachomatis (CT) and Mycoplasma genitalium (MG) using Aptima assays (Hologic, Inc.). NGU was defined as ≥5 polymorphonuclear leukocytes per high-power field plus either urethral symptoms or visible discharge. We estimated incidence of NGU overall, asymptomatic and symptomatic NGU, non-CT/non-MG NGU and CT/MG-associated NGU using Poisson regression for clustered outcomes. We performed relative risk binomial regression for clustered data to identify characteristics associated with incident NGU. RESULTS: From 08/2014–07/2018, 307 participants contributed 109.4 person-years at risk of NGU. Median age was 32 years and 52% were White. At enrollment, 107 men had NGU; of these 88% were symptomatic, 27% had CT and 22% had MG. Fifty men had 60 cases of incident NGU (incidence rate (IR)=56 per 100 person-years [95% confidence interval (CI)=43–74]). Unlike prevalent NGU at enrollment, CT/MG-associated incident NGU was rare (IR=7 [95% CI 4–15]) and most (78%) incident NGU was asymptomatic. Risk factors for incident NGU were ≤high school education (adjusted rate ratio (ARR)=2.45; 1.19–5.00), history of CT (ARR=2.15; 1.08–4.27), history of NGU (ARR=2.67; 1.27–5.62), and NGU at enrollment (ARR=2.03; 1.04–3.98). Neither condom use nor having a new partner were associated with incident NGU; Black race was only associated with incident symptomatic and non-CT/non-MG NGU. CONCLUSION: Incidence of NGU was high, predominantly non-CT/non-MG and asymptomatic. Future studies should investigate the etiology and clinical significance of asymptomatic NGU