The prevalence of any type of oral HPV infection among men participating in this study was 20.0% (95% CI = 14.8%-26.1%). After multivariate regression analysis, any type of oral HPV prevalence was significantly higher among men with a higher mean number of lifetime sexual partners. A series of studies on oral HPV prevalence
[31–35] have recently sampled specific populations (e.g. MSM or HIV + men) from which results of oral HPV prevalence have varied. For example, in Melbourne, Australia the prevalence of oral HPV among MSM’s attending a sexual health center was 13.0%
. This prevalence resulted slightly lower than that reported in similar study settings among MSM’s in Amsterdam (24.4%)
 and among HIV-infected MSM’s in Italy (21.3%)
. Although comparisons with other studies are not possible due to differences in the sample, the prevalence of oral HPV among MSM in our study was 19.3%.
In our study, although a higher prevalence of oral HPV infection was observed among HIV positive men (22.3% in HIV-positive vs. 17.8% in HIV-negative), this association was not significant. Also, neither sexual behavior nor oral sexual practices were significantly associated with any type of oral HPV detection. This may be explained by the selection of a high sexual risk group of men attending a public STI clinic, which lacked enough heterogeneity with regards to some risk factors.
Prevalence of oral HPV significantly increased within increasing age categories. The peak prevalence was found among men aged 55–81 years of age (34.5%). This increasing trend could be explained by an increased oral HPV incidence with age
, persistent and/or reactivated oral HPV infections
 due to loss of immunity as age increases
[17, 37], and/or increased persistence among older individuals
[17, 38]. However, it is important to clarify that although a trend was found between oral HPV and age, the association between these variables did not remain statistically significant after adjusting for lifetime sex partners and lifetime smoking in the multivariate logistic regression model.
The multivariate logistic regression model for any type of oral HPV infection demonstrated an independent significant association with lifetime number of sex partners and a marginal independent association with lifetime smoking, after adjusting for differences in age categories. Increased odds of any type of oral HPV infection among men with increased number of sex partners is supported by the literature
, indicating that oral HPV infection is higher among sexually experienced individuals than by nonsexual contact. The association with lifetime smoking, though marginal, may confirm the biological plausibility associated with oral HPV infection
. Cigarette smoking inhibits a variety of immune responses in the oral cavity
, which may allow for increased HPV persistence
. The oral epithelial abrasion due to the direct exposure to the carcinogens in tobacco may also represent the pathway for increased HPV detection among smokers
The findings of this study need to be interpreted with caution because of its inherent limitations. We acknowledge that perhaps the sample size of 205 men was not sufficient for this type of study. Though this number can be considered fair in other types of research, we found it to be insufficient for this type of setting, especially when creating categories for certain outcome variables and in analyses for associations with clinical characteristics.
Oral HPV infection was measured once, so it was not possible to differentiate between newly acquired, persistent, or reactivated infections
. Site of infection, such as the oral cavity or the oropharynx, was also not possible to differentiate, due to the oral rinse sampling technique used
. We recognize additional limitations in the way some of the behavioral and clinical variables were measured. This study relied upon self-reported data for HIV status, which could lead to misclassification and residual confounding. Among HIV positive men, CD4 T-cell count, viral load and highly active antiretroviral therapy (HAART) use, was not available. Also, the lack of frequency measures for alcohol, tobacco, and marihuana use limited the interpretation of the results. Perhaps measuring recent use, within the past 6 or 12 months, and measuring the quantity of use for these behavioral variables could have provided a more detailed insight on the magnitude of association between these variables and oral HPV in men. Categorizing these variables into more detailed recent use measurements could have increased validity and power.
Also, due to the small sample size among MSM’s, opportunities to determine recent MSM behavior (i.e. last 3 months) and conduct multivariable analyses were not possible. Other limitations include the lack of data regarding the use of condoms and other variables which could help us understand sexual partnering and preventive practices among MSM. Furthermore, we were unable to examine MSM sociocultural contexts, like violence, stigma, homophobia, social networks, and the construction of gender identities. Future studies need to explore these social determinants when attempting to understand the sexual behavior and HPV/HIV-related risks to which the participants of this study setting are exposed in Puerto Rico.
Since the study was conducted in a high risk STI public clinic, our findings are unlikely to be generalizable to populations at lower sexual risk. However, data collected from a highly selective population, such as a public STI clinic, may also offer an opportunity to reach targeted high-risk groups more efficiently than general population-based studies. As described in other studies
[40, 41], participants attending publicly funded STI clinics are likely to be young, uninsured and poor. Therefore, this scenario has helped target oral HPV infection analyses among a vulnerable population.
To our knowledge, this is the first study currently examining the epidemiology of oral HPV infection among men attending a public STI clinic in Puerto Rico. Since previous studies have reported that men in Puerto Rico have a higher incidence and mortality of oropharyngeal cancer as compared to Hispanics in the US
, future studies should further elucidate if potential interactions between alcohol use, tobacco use, and HPV infection may explain the higher burden of oral cancer in this population. Also, preventive efforts in this area are warranted. However, primary preventive interventions in this high sexual risk setting can be too late and ineffective. Since our study demonstrated a high oral HPV prevalence, capacity building and training on malignancies in the oral cavity among the medical staff are recommended. This type of intervention in a high risk setting can be appropriate to reduce complications and comorbidities.