Prevalence and determinants of human papillomavirus infection in men attending vasectomy clinics in Mexico
Article first published online: 17 MAY 2006
Copyright © 2006 Wiley-Liss, Inc.
International Journal of Cancer
Volume 119, Issue 8, pages 1934–1939, 15 October 2006
How to Cite
Vaccarella, S., Lazcano-Ponce, E., Castro-Garduño, J. A., Cruz-Valdez, A., Díaz, V., Schiavon, R., Hernández, P., Kornegay, J. R., Hernández-Avila, M. and Franceschi, S. (2006), Prevalence and determinants of human papillomavirus infection in men attending vasectomy clinics in Mexico. Int. J. Cancer, 119: 1934–1939. doi: 10.1002/ijc.21992
- Issue published online: 11 AUG 2006
- Article first published online: 17 MAY 2006
- Manuscript Accepted: 1 MAR 2006
- Manuscript Received: 13 JAN 2006
- Mexican National Science and Technology Council (Consejo Nacional de Ciencia y Tecnología, CONACYT). Grant Numbers: SALUD-2002-C01-7800, 34468-M
- International Agency for Research on Cancer. Grant Numbers: FI/92/3-5 MEX-4, FIS/03/02
- Instituto Nacional de Salud Pública
- human papillomavirus;
- sexual habits;
- condom use
Large studies of genital human papillomavirus (HPV) infection in men are few and mainly include high-risk groups. We interviewed 779 men who requested a vasectomy in 27 public clinics in 14 states of Mexico. Exfoliated cells were obtained from the scrotum, the shaft of the penis, the top of the penis including the coronal sulcus, the glans and the opening of the meatus. HPV testing was performed using biotinylated L1 consensus primers and reverse line blot. Unconditional logistic regression was used to estimate odds ratios (ORs) of being HPV-positive and corresponding 95% confidence intervals (CIs). The prevalence of any type of HPV was 8.7%. HPV positivity was highest among men below age 25 (13.6%), and lowest among men aged 40 years or older (6.0%). The most commonly found HPV types were, in decreasing order, HPV59, 51, 6, 16 and 58. Lifetime number of sexual partners was associated with HPV positivity (OR for ≥4 vs. 1 partner = 3.7, 95% CI: 2.0–6.8), mainly on account of the strong association with number of occasional and sex-worker partners. Condom use with both regular (OR = 0.4, 95% CI: 0.1–1.0) and sex-worker (OR = 0.1, 95% CI: 0.0–0.3) partners and circumcision (OR = 0.2, 95% CI: 0.1–0.4) were inversely associated with HPV positivity. HPV prevalence in Mexican men was similar to the prevalence found in Mexican women of the same age groups. The association between HPV positivity and lifetime number of sexual partners in the present low-risk male population is one of the strongest ever reported in studies in men. Condom use and circumcision were associated with a strong reduction in HPV prevalence. © 2006 Wiley-Liss, Inc.
Human papillomavirus (HPV) infection, the necessary cause of invasive cervical cancer and its precursor lesions,1 is a very common sexually transmitted disease in women in many populations.2 HPV infection in men causes genital warts,3 and is associated with HPV infection4, 5 and cervical cancer6, 7 in female partners.
Previous studies on genital HPV infection in men showed an approximately equal prevalence of HPV infection in any population in the 2 genders,8 and the existence of a direct, though moderate, association between HPV positivity among men and lifetime number of sexual partners.9, 10 However, contrary to the relatively large amount of information on genital HPV infection in women,2,11 large studies on HPV prevalence in the general male population are few. Furthermore, the majority of studies in men have focused on young individuals12 or high-risk populations [e.g., men attending sexually transmitted disease (STD) clinics9, 13, 14 or enrolled in military service15, 16, 17].
Two previous reports from Mexico12, 17 showed that more than one-third of the young men studied were infected with genital HPV. To further elucidate the characteristics of HPV infection in the general male population, we assessed the prevalence and determinants of infection with 35 HPV types among 779 Mexican men who attended public clinics to undergo vasectomy.
Material and methods
The present study was carried out between January 2003 and September 2004 among men who requested a vasectomy in 27 public clinics in 14 states of Mexico: Baja California Norte, Chihuahua, Nuevo Leon, Sonora, Tamaulipas, Mexico City, Morelos, Mexico State, Jalisco, Michoacan, Campeche, Chiapas, Guerrero and Tabasco.
Individuals were invited to participate by the medical staff and were informed of the purpose of the study and the genital-cell sampling procedure. Only approximately 5% of men invited refused to participate, and thus, a total of 1,043 men were included. Participation was similar in all 14 states. All participants signed an informed consent form, as recommended by the ethics committees of the Instituto Nacional de Salud Pública (INSP) and the International Agency for Research on Cancer (IARC), which approved the study.
Trained interviewers questioned study participants face-to-face using a questionnaire that included information on sociodemographic characteristics, smoking habits, genital hygienic practice and condom use. Information on sexual behavior was also collected and included age at sexual debut and the number and type of female sexual partners (i.e., regular, occasional or sex-worker), and history of sexual intercourse with other men.
Medical examination and specimen collection
Study participants were asked not to wash their genitals for at least 12 hr before the genital examination, which was conducted by specially trained primary care physicians before vasectomy. Circumcision status and the presence of urinary tract symptoms and penile lesions were also assessed by study physicians. Samples were collected using a cytobrush (Cytobrush®Plus Sterile, Medscand Medical Inc., Hollywood, FL) moistened in phosphate-buffered saline (PBS). The penis was brushed in a continuous rotational movement, from bottom to top, starting at the middle third of the scrotum. After retraction of the prepuce (for uncircumcised men), the coronal sulcus, the glans and the opening of the meatus were also brushed with the same device. The cytobrush was then placed in a bar-coded 20-ml Falcon tube and sent to the INSP for HPV testing. The cells were centrifuged, and the cell pellets suspended in 2 aliquots of 2.5 ml of PBS, and then frozen at −70°C until tested.
HPV DNA detection techniques
HPV testing was performed on exfoliated cells at the INSP (Cuernavaca, Mexico). A first screening was performed to determine the overall presence of HPV DNA by strip assay, using the reverse line blot format as described by Gravitt et al.18,19 Briefly, HPV DNA was amplified using the biotinylated L1 consensus primers. For HPV typing, PCR products were hybridized to probes immobilized on nylon strips. Each strip contained 37 probe lines, i.e., 35 type-specific probe lines (HPV6, 11, 16, 18, 26, 31, 33, 35, 39, 40, 42, 45, 51–56, 58, 59, 61, 62, 64, 66–73, 81–84) and 2 for high and low concentrations of β-globin genes. Hybridization signals were detected by color development, and strip interpretation was performed using an acetate overlay indicating the position of each type-specific probe. Hybridization results were read independently by 2 reviewers. Each reviewer classified the specimen as positive or negative. Discrepancies in classification between the 2 reviewers were resolved by a joint review. All reagents were provided by Roche Molecular Systems, Inc. (Alameda, CA).
Overall, 264 (25.3%) men tested negative for β-globin and were excluded from the present analysis, leaving a total of 779 subjects. HPV types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 68, 73 and 82 were considered high-risk types, by analogy with the corresponding classification of HPV types in women.20 Other types, including HPV 26, 53, 66, which were considered as “probably high-risk” in the HPV classification,20 were included in the analyses as low-risk types.
Regular sexual partners were defined as lifetime female partners with whom the sexual relationship had lasted for at least 6 months. Occasional sexual partners were defined as lifetime female partners with whom the sexual relationship had lasted less than 6 months. The lifetime number of sexual partners was calculated using the information on regular, occasional and sex-worker partners. A socioeconomic index was computed using housing standards and ownership of different household appliances, and was classified in 3 levels (low, medium and high).
Unconditional logistic regression was used to estimate odds ratios (ORs) of being HPV-positive and corresponding 95% confidence intervals (CIs), according to several characteristics. All ORs were adjusted for age group (<25, 25–29, 30–34, 35–39, 40–44, ≥45) and, when specified, for lifetime number of sexual partners. Tests for linear trend were performed, giving an increasing score for each level of the categorized variable and fitting them into the model as continuous variables.
Among the 779 men included in the present analysis, the mean age was 34.0 years. As expected, the majority (75.1%) of men who requested a vasectomy was married. The prevalence of any type of HPV was 8.7% (Table I), and the corresponding prevalence, age-standardized to the world standard population21 was 9.5%. In total, 52 men had single-type and 16 had multiple-type infection (10 double, 5 triple and 1 quadruple infections). High-risk HPV types were more frequent (6.0% of all men) than low-risk types (4.2%). The most commonly found high-risk types in either single- or multiple-type infections were HPV59 (1.5%), 51 (1.3%), 16 (0.8%) and 58 (0.8%). HPV6 was the most commonly found low-risk type (0.9%). Total HPV positivity among men whose genital cell sample was β-globin-negative was 7.6% (data not shown).
|HPV status||Single||Multiple||Total||Percent of total population|
HPV positivity was highest among men under age 25 (13.6%), and lowest among men aged 40 years or above (6.0%, Fig. 1). High-risk HPV types were more frequently detected, than low-risk types, in all age groups, but the difference was more marked in younger age groups (Fig. 1).
Table II shows the relationship between HPV positivity and age, and major indicators of sexual behavior after adjustment for age. Cohabitation or other marital status was not significantly related to HPV positivity. Age at first sexual intercourse and number of sexual relationships before 20 years of age did not show significant tests for linear trend. The median number of lifetime sexual partners was 2. Lifetime number of sexual partners was directly associated with HPV positivity (OR for ≥4 vs. 1 partner = 3.7, 95% CI: 2.0–6.8). The OR for 3 or more regular partners (1.4, 95% CI: 0.8–2.6) was increased, though not significantly, when compared to 1 regular partner. Sixteen percent of study men reported intercourse with occasional partners and 27% with sex-worker partners. Men who had 3 or more sexual contacts with occasional (OR = 3.4, 95% CI: 1.7–7.0) or sex-worker partners (OR = 2.6, 95% CI: 1.3–5.4) had a significantly increased risk when compared to men who did not have any occasional or sex-worker partner. Twenty-five percent of the study population declared to have used condom. Condom use with regular (OR = 0.4, 95% CI: 0.1–1.0) and sex-worker (OR = 0.1, 95% CI: 0.0–0.3) partners was associated with a reduction of the risk of being HPV-positive. Washing genitals always or often after sexual intercourse was associated with an increased OR for HPV positivity of borderline statistical significance (OR = 1.7, 95% CI: 1.0–2.9). Thirty men reported to have had sexual intercourse with other men, and none were found to be HPV-positive (data not shown).
|Characteristics||N||HPV-positive (%)||OR (95% CI)1|
|Linear trend test||χ2 (1 df) = 3.6; p = 0.06|
|Age at first sexual intercourse|
|Linear trend test||χ2 (1 df) = 0.6; p = 0.42|
|Number of sexual partners before 20 years|
|Linear trend test||χ2 (1 df) = 1.8; p = 0.18|
|Lifetime number of sexual partners|
|Linear trend test||χ2 (1 df) = 17.4; p < 0.0001|
|Number of regular partners|
|Linear trend test||χ2 (1 df) = 1.3; p = 0.25|
|Number of occasional partners|
|Linear trend test||χ2 (1 df) = 24.0; p < 0.0001|
|Number of sex-worker partners|
|Linear trend test||χ2 (1 df) = 16.9; p < 0.0001|
|Condom use with regular partners3|
|Condom use with sex-worker partners3,4|
|Washing genitals after intercourse3|
|Always or often||430||10.7||1.7 (1.0–2.9)|
The combined effects of having had regular, occasional and sex-worker partners are shown in Table III. Men who, in addition to 1 regular partner, had occasional (OR = 2.7, 95% CI: 0.9–7.9) or sex-worker partners (OR = 3.8, 95% CI: 1.8–8.0) showed increased risks of being HPV-positive. HPV positivity was not increased (OR = 0.7, 95% CI: 0.3–1.8) among men who reported 2 regular partners or more, but no occasional or sex-worker partners. However, the ORs for having had 2 regular partners or more, in addition to occasional or sex-worker partners, were 4.3 (95% CI: 1.4–13.0) and 5.6 (95% CI: 2.7–11.2), respectively, when compared to having had 1 regular partner and no occasional or sex-worker partners (Table III).
|Number of regular partners||Occasional = no, sex-worker = no||Occasional = yes, sex-worker = no||Sex-worker = yes|
|OR (95% CI)||12||2.7 (0.9–7.9)||3.8 (1.8–8.0)|
|OR (95% CI)||0.7 (0.3–1.8)||4.3 (1.4–13.0)||5.6 (2.7–11.2)|
Table IV shows the ORs for HPV positivity by selected characteristics in a model adjusted for age and lifetime number of sexual partners. Geographical area of residence in Mexico, educational level, socioeconomic index and religion were not associated with HPV positivity in our study. Ever smokers represented 57.3% of the study population. Current (OR = 2.3, 95% CI: 1.1–4.6) and former (OR = 2.3, 95% CI: 1.2–4.3) smokers had a significantly higher risk of being HPV-positive than never-smokers. Circumcised men made up 31.7% of our study population. A strong and significant inverse association was found between HPV positivity and being circumcised (OR = 0.2, 95% CI: 0.1–0.4).
|Characteristics||N||HPV positive (%)||OR (95% CI)1|
|Years of education|
|Linear trend test||χ2 (1 df) = 0.7; p = 0.39|
|Linear trend test||χ2 (1 df) = 0.1; p = 0.73|
No substantial differences in relation to the major risk factors were found when we considered the positivity for high-risk and low-risk HPV types separately (data not shown).
Penile lesions were found in 128 (16.4%) men, of whom 40 (5.1%) had condyloma acuminata, and 14 (1.8%) had penile ulcer. HPV prevalence among men with condyloma acuminata (7.5%) was not higher than that among men with no penile lesions (8.9%). Among the 3 HPV-positive men with condyloma acuminata, 2 of them had a single infection with HPV52 and 26, respectively, and 1 had a double infection with HPV59 and 84.
Our present study of HPV infection among men attending vasectomy clinics in Mexico is one of the largest studies ever conducted, and one of the few not to be restricted to young men12, 16, 17 or STD patients.13 The overall prevalence of HPV positivity was 8.7%, and the prevalence among the most sexually active men (≥4 sexual partners) was 14.9%. The age-standardized HPV prevalence based on the world standard population was 9.5%, similar to the age-standardized prevalence (10.8%) found among cytologically normal women of the same age group (i.e., <55 years) in the state of Morelos, Mexico.22 In addition, the age-specific prevalence pattern of the infection in men, with a peak (13.6%) in HPV positivity among men under 25 years of age, and a subsequent steady decline until 40 years or more (6.0%), was also similar to the distribution found in women.22 The presence of a peak in HPV prevalence at a younger ages is also in agreement with the high HPV positivity reported previously in Mexico among men12, 17 who, however, were more sexually active and, hence, more often HPV-positive (43–45%) than the present group of men attending vasectomy clinics.
The spectrum of HPV types found in the present study was similar to that found in Mexican soldiers17: HPV59 was the most prevalent type in both studies, and HPV51, 16 and 58 were also frequently detected. As already noted,17 the type-specific distribution of HPV in men seems different from the one observed in Mexican women22, 23 where HPV59 was relatively rarely found, and HPV16 was by far the most common type. Also among female Mexican sex-workers23 HPV 16, not 59, was the most common HPV type.
We did not detect any significant trend with number of sexual relationships before 20 years of age, contrary to findings among young Mexican soldiers.17 This difference suggests that the number of sexual partners before 20 years could be a good predictor of HPV prevalence, but only among young people.
Conversely, the association between HPV positivity and lifetime number of sexual partners in our report is one of the strongest ever reported in studies in men.9,13,14,17 In the study of Mexican soldiers, for instance, the OR for HPV positivity among men who reported a number of lifetime sexual partners over 5 vs. 1 was only 1.3 (nonsignificant).17 As already noted,24 the apparent association of HPV positivity with sexual behavior tends to weaken in studies of high-risk populations or subpopulations where the background prevalence of HPV is very high.
We specifically tried to disentangle the influence of different types of female sexual partners, a difficult task on account of the positive correlation between high-risk sexual behaviors. As expected, we found that multiple occasional and sex-worker partners were more strongly associated with HPV positivity than multiple regular partners. However, the association of HPV positivity with the number of regular partners seemed to be increased by the concurrent report of occasional and sex-worker partners. This suggests that among the most sexually active men the distinction between regular and occasional partners is blurred.
Our study found that current and former smokers had a more than 2-fold higher risk of being infected with HPV than nonsmokers, whereas Lajous et al.17 did not report any association among Mexican soldiers. Although the association with smoking was not eliminated by adjustment for lifetime number of sexual partners, we cannot exclude some residual confounding from high-risk sexual behavior.
Only 13% of our study population reported condom use with regular partners, while among the 208 subjects who had had sex-worker partners the percentage of condom use was 52%. In both circumstances, condom use was associated with a strongly decreased risk of HPV positivity. Previous studies on the effect of condom use on genital infection in men14, 16, 17 and in women25, 26, 27 and on HPV transmission within couples28 showed less clear evidence of protection. Inconsistency in the apparent influence of condom use is not surprising on account of the differences in the way condom use was practiced and assessed in different studies.
The strongly reduced risk of HPV positivity that we found for circumcised men confirms previous reports by Castellsagué et al.10 and Lajous et al.17 Our results, which are unlikely to be confounded by other factors, are based on the assessment of the circumcision status made by study physicians. A possible explanation for our findings is that circumcision substantially improves genital hygiene and decreases the risk of acquisition or persistence of HPV infection.
Among the limitations of this study, the relatively high percentage (25%) of β-globin-negative samples is worth mentioning. As already reported for genital Chlamydia trachomatis,29 β-globin-negative samples can cause misleading HPV findings. Therefore, we excluded men with a β-globin-negative sample from our present analyses. It is reassuring, however, that the subjects excluded from the analyses because of their inadequate genital cell specimen did not substantially differ, with respect to age and lifetime number of sexual partners, from the subjects with a valid HPV result (data not shown). Cell sampling from the urethra was not performed in the present study, but we have previously shown that the availability of a sample from the urethra only slightly increases HPV detection from the male genital tract.30 As usual, inaccuracies in the report of lifetime number of sexual partners and, in particular, occasional and sex-worker partners, cannot be excluded. The study setting (vasectomy clinics) and the relative lack of stigma that exists in Mexico concerning male sexual behavior should have reduced under-reporting of sexual partners.
The large study size, country-wide sampling, high participation and use of validated methods for genital cell collection30 and HPV testing19 are important strengths of our present study. Furthermore, as vasectomy is an increasingly common contraceptive method in Mexico,31 our study population can probably be considered representative of married young and middle-aged adults in the country.
The authors are grateful for the invaluable collaboration of the patients and staff of the following vasectomy clinics: Baja California Norte (Tijuana, Mexicali, Ensenada); Nuevo León (Monterrey); Sonora (Hermosillo, Puerto Peñasco); Tamaulipas (Nuevo Laredo); Aguascalientes (Aguascalientes); Mexico City (Gustavo Madero, Alvaro Obregón); Jalisco (Guadalajara); Mexico State (Ciudad Nezahualcoyotl, Naucalpan, Texcoco, Chiconcuac); Michoacan (Morelia); Campeche (Campeche); Chiapas (San Cristóbal de las Casas, Tapachula); Morelos (Cuernavaca, Yautepec); Guerrero (Acapulco) and Puebla (Puebla).
Janet R. Kornegay is employed by Roche Molecular Systems, which produces the HPV test for primary cervical cancer screening and triage of women as well as for research use. All other authors have no conflict of interest to declare.
- 11IARC. Human papillomavirus. Monographs on the evaluation of carcinogenic risks to humans, vol. 64. Lyon: International Agency for Research on Cancer, 1995.
- 21ParkinDM, WhelanSL, FerlayJ, ThomasDB, TeppoL, eds. Cancer incidence in five continents, vol. VIII. Lyon: IARC, 2002. IARC Scientific Publications No: 155.
- 29An important proportion of genital samples submitted for Chlamydia trachomatis detection by PCR contain small amounts of cellular DNA as measured by β-globin gene amplification. J Clin Microbiol 2000; 38: 2512–15., , , , , .
- 311995. Available at: www.engenderhealth.org/pubs/workpap/wp8/wp_8.html, , , , . A successful national program for expanding vasectomy services: the experience of the Instituto Mexicano del Seguro Social. AVSC Working Paper No. 8. June