Prevalence of and risk factors for syphilis in Brazilian armed forces conscripts
- Denis Ribeiro1,2,
- Erika Fazito Rezende1,
- Valdir Monteiro Pinto1,2,
- Gerson Fernando Mendes Pereira1,
- Angélica Espinosa Miranda2
- 1STD/AIDS and Viral Hepatitis Department, Ministry of Health, Brasília, Brazil
- 2Infectious Diseases Unit, Federal University of Espírito Santo, Vitória, Brazil
- Correspondence to Dr Angélica Espinosa Miranda, Av. Marechal Campos, 1468 – Vitoria – ES – 29100-240, Brazil;
Contributors DR was in charge of the conception and text development and composition of results. EFR was the coordinator of the field study and participated in the development of the methodology. VMP participated in the text conception and was responsible for the composition of results and development of tables. GFMP coordinated the survey and participated in the development of the methodology. AEM was in charge of the conception and text development and participated in the development of the methodology and composition of results.
- Accepted 9 October 2011
- Published Online First 28 October 2011
Objective The aim of this study was to describe the prevalence of syphilis by geographical region and the frequency of behaviours and symptoms related to sexually transmitted diseases (STD).
Methods A cross-sectional study was performed with Brazilian conscripts in 2007. They answered a self-administered questionnaire on demographic issues, sexual practices, condom use and STD symptoms. They had a blood sample collected for a syphilis test.
Results A total of 35 460 conscripts answered the questionnaire and 75.5% reported previous sexual intercourse. Overall syphilis prevalence was 0.53% (95% CI 0.45% to 0.61%). By geographical region: northern (0.85%), northeast (0.82%), midwest (0.49%), southeast (0.34%) and southern region (0.26%). The final logistic regression model showed an association among having had syphilis and being 17 years old (OR 1.3; 95% CI 1.05 to 1.73), having up to 8 years of schooling (OR 1.5; 95% CI 1.03 to 2.22), living in the northern/northeast region (OR 1.2; 95% CI 1.04 to 1.36), being men who have sex with men (OR 4.5; 95% CI 2.59 to 7.81), reporting a previous history of STD (OR 2.7; 95% CI 1.03 to 6.99) and genital ulcers (OR 2.6; 95% CI 1.59 to 4.26).
Conclusions Addressing young people at the time of military enlistment may be a good time to consider new strategies for accessing and counselling this population, thus allowing the implementation of a more appropriate healthcare policy.
Monitoring disease prevalence is an important component of the epidemiological surveillance of sexually transmitted diseases (STD).1 The Brazilian programme for STD/AIDS has developed a programme that is a pioneer in Latin America for monitoring HIV and syphilis. Based on the analysis of tendencies shown by these data on the AIDS epidemic and syphilis infection, prevention and control strategies are defined.2
Young men are a population group in which it is very important to follow sexual behaviours that represent a risk for STD. The conscripts are an easy population to reach, covering all social classes and the entire national territory.3 Military service is mandatory for 1 year for men from 17 to 20 years old in Brazil and annually they must go to a military entrance processing station (MEPS) for enlistment. The objectives of this study were to determine the prevalence of syphilis by geographical region and to identify correlated factors and clinical symptoms associated with syphilis in conscripts.
A cross-sectional study was performed among young men at enlistment in military service in 2007. The sampling was prepared in two stages. MEPS were chosen in the first stage and the conscripts in the second stage. The cluster strata were defined in proportion to the geographical region (northern, northeast, southeast, southern and midwest), the size of the municipality in which the MEPS were located (<50 000 inhabitants; between 50 000 and 200 000 inhabitants and >200 000 inhabitants) and the number of young men in each region.
Each conscript answered a self-administered questionnaire containing information on demographic characteristics, sexual practices, regular condom use and the occurrence of STD signs/symptoms. A blood sample also was collected for syphilis using the ELISA method (enzyme immunoassay IgG and IgM-Trepanostika TP; bioMérieux, Lyon, France).
The sample size was calculated to estimate the national and regional prevalence in conscripts, with a 95% CI for 1.5% bilateral size. A prevalence of 0.1 was taken as the basis.3 The calculated sample size was 34 263 and, considering a 20% loss and a sampling design effect of 1.3, a final sample size of approximately 39 000 conscripts. It represents approximately 6% of the Brazilian conscript population.
Syphilis prevalence was estimated based on positive treponemal tests. The corresponding 95% CI was calculated. The clustered character of the data was taken into account. Possible associations between syphilis and correlated factors were tested using χ2 tests and OR with respective CI. All variables significant at p<0.15 were included in the multivariate logistic regression.
The Brazilian National Research Ethics Committee approved this project (no 589/2006). Participation in the study was voluntary. Participants received counselling about further testing and treatment in the case of positive test results.
A total of 35 460 (88.7%) from 39 000 conscripts selected answered the questionnaire and was included in the study. One hundred and forty-seven cases had positive treponemal syphilis test results, the prevalence was 0.55% (95% CI 0.45% to 0.61%). The prevalence of syphilis by geographical region was: northern (0.85%; 95% CI 0.54 to 1.16); northeast (0.82%; 95% CI 0.65 to 0.99); southeast (0.34%; 95% CI 0.24 to 0.44); southern (0.26%; 95% CI 0.12 to 1.76) and midwest (0.49%; 95% CI 0.22 to 0.76). There were no positive test results among conscripts who did not report sexual intercourse.
The mean age was 18 years (SD 0.7). Having up to 8 years of schooling (51.9% vs 34.8%, p=0.001) and having left school (34.6% vs 26.3%, p=0.002) were correlated factors for positive treponemal test results under the bivariate analysis.
A total of 26 417 (74.5%) young men had already had sexual intercourse involving penetration and were therefore considered to be sexually active. Table 1 shows the behavioural and clinical characteristics of sexually active conscripts. A previous history of syphilis (3.4% vs 0.3%, p=0.001) and condylomatosis (3.4% vs 0.6%, p=0.001) were more frequent in conscripts with syphilis. Genital ulcers (19.0% vs 6.3%, p=0.001) and urethral discharge (7.5% vs 2.4%, p=0.021) were also more frequent among conscripts with syphilis.
Reporting of STD-related symptoms was not associated with the size of the municipality in which the conscripts lived, but there was a statistically significant association between the reporting of previous STD symptoms and the region in which the conscripts lived. Conscripts living in the northern region were those who most often reported at least one STD-related sign or symptom (18.5%).
The final logistic regression model showed an association between having had syphilis and being 17 years old (OR 1.3; 95% CI 1.05 to 1.73), p=0.018; having 8 years or less of schooling (OR 1.5; 95% CI 1.03 to 2.22), p=0.035; living in the northern/northeast regions (OR 1.2; 95% CI 1.04 to 1.36), p=0.011; being men who have sex with men (MSM) (OR 4.5; 95% CI 2.59 to 7.81), p=001; reporting a previous history of STD (OR 2.7; 95% CI 1.03 to 6.99), p=0.043; and genital ulcers (OR 2.6; 95% CI 1.59 to 4.26), p=0.001.
Our results show a low prevalence of syphilis among conscripts in Brazil. The prevalence was higher in the northern and northeast regions, where rates were more than double that found in the midwest, southeast and southern regions. A previous study in Brazil found a ratio of 0.85% in conscripts.3 Even though a reduction has been observed in this population, the presence of syphilis needs to be monitored.
Variables associated with syphilis in this study were: being 17 years old, having elementary education, living in the northern/northeast regions, being MSM, reporting a previous history of STD, and reporting genital ulcers. The youngest age being associated with syphilis could be explained by spontaneity or unplanned sexual intercourse and difficulties in negotiating condoms when they had just started sexual life. The other variables corroborate other studies that demonstrated that young people with low levels of schooling and living in precarious socioeconomic situations are more susceptible to STD.4 The elevated prevalence of irregular condom use among adolescents of both sexes and how such behaviour exposes young people to STD are described in other studies.4–6 A previous study in Brazilian conscripts showed an association between HIV infection and STD-related problems, especially syphilis. A higher frequency of STD-related problems was also observed in the northern region.3
The possibility of response bias having occurred cannot be discounted because of the tendency for socially acceptable answers to be given. We also believe that the bias caused by using a treponemal test to diagnose syphilis has been minimised in this study, given that the population is young and has begun its sex life more recently. As such, it has less chance of having had previous exposure to Treponema pallidum and, therefore, it may be appropriate to consider the result as being a proxy of active syphilis.
Young people of both sexes are normally more susceptible to STD, both because of the need to have new experiences that lead them to having a higher risk sexual activities, and also because of the greater difficulty in negotiating safer sex. Rates of condom use have increased among young people. However, inconsistent condom use and high rates of partner acquisition contribute to a higher risk of STD.7 8 The 15–24 years age group has the highest rates of STD in the majority of countries.5 6 Other authors have associated starting one's sex life at an earlier age, low education levels and low income with an increased risk of STD and AIDS.4 9
These data highlight the need for education, prevention and treatment measures. Addressing the young at the time of military enlistment may be a good time to consider new strategies for accessing and counselling this population, thus allowing the implementation of more appropriate healthcare policy.
Syphilis was associated with being younger, less educated, living in the northern/northeast regions, being MSM, reporting previous STD and genital ulcers.
Military service is a good time for accessing and counselling young men.
It is an opportunity for STD education programmes to youths and for planning appropriate healthcare policy.
Offering benefits with early diagnosis and treatment is a strategy to control STD in young men.
Funding The Brazilian Ministry of Health provided funding for this study.
Competing interests None.
Patient consent Obtained.
Ethics approval Ethics approval was received from the Brazilian National Research Ethics Committee (report no 589/2006).
Provenance and peer review Not commissioned; externally peer reviewed.