CHLAMYDIA TRACHOMATIS (CT) IS THE MOST prevalent bacterial sexually transmitted disease in Norway as well as in other European countries1 and in the United States.2,3 CT infections are easily cured by a single dose of oral antibiotics, but detection is complicated by their often asymptomatic nature in both men and women. Although long-term consequences for female reproductive health are well documented,4 it remains controversial whether CT infections affect male fertility.5
After urine-based nucleic acid amplification assays became available for CT screening, research in CT infections among males has proliferated.6–10 In Norway, however, knowledge on CT infections among men is sparse. A study based on routine laboratory data showed that CT prevalence among young Norwegian male first-time testers is considerably higher than among female first-time testers, whereas male testing rates are low.11 Low testing rates among men compared with women have also been reported from Denmark12 and the United Kingdom.13 Surveys among health personnel indicate that health personnel often consider CT as a women's health issue.14 However, both sexes need to be tested, and Norwegian health authorities recommend that people of both sexes younger than 25 years old with a new sexual partner should be tested for CT.
The present cross-sectional study was conducted to assess CT prevalence, risk factors for infection, and genitourinary symptoms among young sexually active men in 2 Norwegian cities.
Materials and Methods
The study was approved by the Regional Committees for Medical Research Ethics and the Norwegian Data Inspectorate. Each participant gave written informed consent to merge questionnaire data on sexual behavior with the CT test result.
During the period April through October 2005, we recruited men 18 to 30 years old in the cities of Oslo and Trondheim, Norway. These cities have 530,000 and 160,000 inhabitants, respectively, both with large student populations. At the student health centers, male patients were consecutively informed about the study and invited to participate. We invited men to participate in the study at stands on the university campuses, where we also informed about CT infections and men's responsibility for preventing reproductive sequelae among females (13 occasions). Participants completed a questionnaire on sexual behavior and delivered a sample of first-void urine for CT testing.
First-void urine samples were collected in polypropylene containers according to the instructions of the manufacturer. The containers were labeled with the participant's allocation number and the 11-digit personal identifier unique to each Norwegian citizen. Urine samples were analyzed within 3 days by strand displacement amplification (BD ProbeTec ET; Becton Dickinson) at the Ullevål University Hospital, Oslo, or by polymerase chain reaction (PCR; Amplicor; Roche Molecular Systems) at the Trondheim University Hospital. All weak positive tests were confirmed by repeat analysis (same test).
Follow Up of Men With Positive Tests
In each city, the laboratories sent test results by personal identifier to the student health centers. Men with positive tests were contacted by mobile phone, e-mail, or a mailed letter and were rapidly given an appointment with a physician for treatment.
A list of test results by allocation number was sent by each laboratory to the study coordinator. Allocation numbers were used for merging test result data with questionnaire data. Data were analyzed using SPSS for Windows, version 13.0 (SPSS, Chicago, IL).
We handled missing data in key variables in the questionnaire as described subsequently. Missing data on age were complemented by using year of birth from laboratory data. Twenty-four men who did not report marital status were assigned status as single. Because this was a young population, we chose to enter the reported number of partners in the previous 12 months as the number of lifetime partners when this information was missing (10 cases). Eleven men reported having had sexual intercourse during the prior 6 months and no male partners, but provided no answer to the question on the number of female partners during the previous 6 months. In these cases, we chose to enter the number of female partners during the previous 12 months divided by 2 (rounded up). Twelve men who did not answer whether they used a condom during their last intercourse were categorized as nonusers. Finally, 7 men who did not answer any questions on previous CT tests were categorized as having no prior test.
We used log-likelihood tests for univariable and multivariable analyses. Predictors of CT infection were identified using multivariable logistic regression analyses. Variables with a P ≤0.10 in univariable analysis were used as input to the model. Final variable selection was based on the forward-stepwise method.15
A total of 1,119 men consented to participate in the study and handed in urine samples and a questionnaire. We excluded 26 men who handed in blank questionnaires, 2 men below 18 years of age, 25 men above 30 years of age, and one man who had been told to participate in the project by his girlfriend who recently had tested positive for CT. After further exclusion of 33 men who answered that they had never had sexual intercourse, data from 1,032 men were eligible for analyses.
The mean age of the participants in this study was 23.6 years (standard deviation ± 2.5 years). Geographically, more participants were recruited in Oslo than in Trondheim (Table 1). Most men in the study population were single (59%), and nearly 90% were students.
The mean age at first intercourse was 17.5 years (standard deviation ± 2.2 years). Forty-five men (4.4%) answered that they had ever had sexual intercourse with a male partner. The median total number of lifetime partners was 7 (25th and 75th percentiles: 3 and 13, respectively). The major proportion of study participants answered that they had been engaged in sexual intercourse during the previous 12 months (95%). The median number of female partners during the previous 12 months was 2 (25th and 75th percentiles: 1 and 4, respectively). Most participants answered that they had been engaged in sexual intercourse during the previous 6 months (92%). The median number of female partners during the previous 6 months was one (25th and 75th percentiles: 1 and 3, respectively).
Table 1 displays demographic and sexual behavior characteristics among participants. The major proportion of study participants (76%) reported not using a condom at last intercourse, and most men (57%) had not been tested for CT previously. Approximately one in 5 men reported having had genitourinary symptoms during the previous 30 days.
There were only minor differences between men recruited in Trondheim and Oslo regarding age, sexual behavioral characteristics, and prior CT tests (data not shown). More men in Oslo than in Trondheim reported being married or cohabitating (18% vs. 8%).
Prevalence of Chlamydia trachomatis Infection
Overall, 7.8% (81 of 1,032) of the study participants were CT-positive. Prevalence was higher among the 21 to 25 year olds (9.0%) compared with younger (5.3%) and older age groups (5.1%), albeit not significantly. Among the 45 men who reported having ever had a male sexual partner, only one had a positive test. This man also reported having had female sexual partners.
In univariable analysis, recruitment site, marital status, number of lifetime partners, number of female partners in the last 6 months, number of new female partners in the last 6 months, and genitourinary symptoms during the last 30 days were all significant risk factors for CT infection, whereas condom use at last intercourse was a preventive factor (Table 1). Young age (≤17 years) at first intercourse was not significantly associated with a higher risk for CT infection.
Overall, 22% (226 of 1,032) of men included to the study reported genitourinary symptoms during the previous 30 days. The proportion reporting symptoms was considerably higher among men recruited at the health centers (29% [153 of 525]) than among men recruited at the campuses (14% [73 of 507]).
Among men testing positive for CT, 46% (37 of 81) reported having had genitourinary symptoms in the previous 30 days, whereas 20% (189 of 951) of men testing negative for CT reported such symptoms. The CT prevalence among men without and with self-reported symptoms during the previous 30 days was 5.5% and 16.4%, respectively (Table 1).
Table 2 shows a more detailed analysis of self-reported symptoms. A burning sensation on urination and penile discharge were the symptoms distinguishing men with CT the most from men without CT. One in 3 men reporting either of these symptoms was CT-positive.
All variables with a P value <0.10 from Tables 1 and 2 were included in a multivariable regression model. Based on the data in Table 1, we recoded missing data in age at first intercourse to “≤17 years.” In multivariable analysis including the full study population, ≥5 lifetime sexual partners, burning sensation on urination, and penile discharge were significant risk factors for infection, whereas condom use at last intercourse was a preventive factor (Table 3). There were no significant interactions between the variables included in this model.
In multivariable modeling including only men without symptoms (prevalence 5.5%, N = 806), we achieved similar risk estimates for ≥5 lifetime partners (adjusted odds ratio [aOR]: 2.4, 95% confidence interval [CI]: 1.1–5.2) and condom use at last intercourse (aOR: 0.3, 95% CI: 0.1–0.9) as in the full model.
When restricting the analysis to the 507 participants not seeking care at the health centers (prevalence 5.5%), a burning sensation on urination (aOR: 6.7, 95% CI: 2.2–20.3) and a high number of lifetime partners (aOR: 3.4, 95% CI: 1.1–10.0) were identified as risk factors.
In this cross-sectional study among Norwegian men 18 to 30 years old, we found a CT prevalence of 7.8% in the total study population and 5.5% among asymptomatic men. Our findings are consistent with those of other studies on CT prevalence involving young men outside sexually transmitted disease clinic settings. For instance, in a large cross-sectional study from the United States (random population sample), a CT prevalence of 3.7% was found among men aged 18 to 26 years,16 whereas a study among male Brazilian military conscripts aged 17 to 24 years showed a prevalence of 5.0%.6 Furthermore, a prevalence of 5.9% was reported from an Irish study among men 17 to 35 years old recruited at sports venues and at an orthopedic outpatient clinic.9 In a random British population sample, however, the prevalence among men aged 18 to 24 years was lower than in our study (2.7%).7
Several studies have shown a peak in CT prevalence among men in the age group 20 to 24 years,6,17 whereas such an age effect has not been revealed in other studies.8,9,16 In the current study, we observed that CT prevalence peaked at age 21 to 25, however not significantly different from the younger or older age groups.
A sexual behavior with frequent sexual encounters with new partners has repeatedly been identified as a risk factor for CT infection among males.6–8 In the current study, multivariable analyses showed that the total number of lifetime partners was a stronger predictor for CT infection than the number of female partners during the previous 6 months or the number of new female partners during the previous 6 months. However, CT prevalence among men reporting one or none female partners in the previous 6 months or no new partners in this time period was the same as in the total population of asymptomatic men. Natural history studies of CT infection among women have shown that more than half the infections are persistent after 12 months.18 We have not been able to identify CT natural history studies among men. Provided a similar natural history in men, it seems reasonable that the sexual history extending the previous 6 months is important for predicting CT status.
We observed that condom use at last intercourse was a preventive factor for CT infection. There were no differences in the number of partners in the previous 6 months between men who answered that they used a condom at their last intercourse and men who answered that they did not (data not shown). Condom use has in several studies been identified as a factor associated with reduced risk of CT transmission in both men and women.19 We observed lower CT prevalence among men answering that they always used condoms (1.5% [N = 67]) and also among men who answered that they consistently used a condom when they had a new sexual partner (3.2% [N = 220]). However, men answering “yes” to the questions on consistent condom use/consistent condom use with new partner had a lower sexual activity measured as the number of sexual partners during the previous 6 months compared with men answering “no” to these questions.
We finally identified self-reported genitourinary symptoms as a factor predicting CT positivity, as also found by others.8 In our data, penile discharge and a burning sensation at urination were the most prominent symptoms of CT infection. Although the majority of CT-positive men in our study had no symptoms, the asymptomatic proportion was lower in our study compared with previous reports.8,10,20 Nearly one third of men seeking care at the health centers reported symptoms compared with one in 6 men recruited at the campuses. It therefore seems probable that a relatively large proportion of men recruited at the health centers were seeking care for genitourinary symptoms. We found a 16.4% CT prevalence among men with symptoms. In a recent Norwegian study based on routinely collected laboratory data, CT prevalence ranged from 15% to 20% for male first-time testers aged 15 to 24 years, whereas testing rates were low.11 Together with the findings in the current study, these data indicate that Norwegian men are not likely to be tested in routine settings unless they have genitourinary symptoms.
In summary, this study shows that the CT prevalence among Norwegian men is relatively high. Screening strategies targeting increased male testing should be implemented.
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