2.1 Study design and methods

Men who had been referred to an outsourced testing center (U2Bio) for HPV testing at hospitals nationwide (including primary hospitals with 30 or fewer beds, secondary hospitals with 30–300 beds, and tertiary hospitals with more than 300 beds) between January 2020 and June 2023 were included. They mainly visited the hospital owing to suspected STIs. All personal information except sex and age was removed, and only test result data were collected. After sample collection, deoxyribonucleic acid (DNA) extraction and multiplex real-time polymerase chain reaction (RT-PCR) were conducted to identify HPV genotypes. All testing procedures adhered to the manufacturer’s protocol.

Swabs and tissue, urine and other samples, including semen and prostatic fluid, were collected. No data were collected regarding the anatomical site of swab collection. Swabs were collected by rubbing a sterile cotton swab on the affected area. Tissue was obtained by biopsy, and urine was collected once. DNA was extracted from samples within 48 h using QIAsymphony (SP type, Qiagen, Hilden, Germany) and refrigerated at 4 °C until testing. The OmniPlex™-HPV kit (GM 3300, Genematrix, Seongnam, Korea) with a CFX96 real-time thermocycler (Bio-Rad, Hercules, CA, USA) was used to perform RT-PCR. The reaction mixture included 2.5 mM deoxynucleotide triphosphates (5 µL), 10× reaction buffer (5 µL), primer mixture (20 pmol), Taq polymerase (0.5 µL), and distilled water adjusted to a final volume of 40 µL. Subsequently, 10 µL of each sample was added to the mixture immediately before the reaction. The PCR conditions involved denaturation at 94 °C for 1 min, annealing at 51 °C for 1 min, and extension at 72 °C for 1 min, repeated for 35 cycles. Finally, extension was carried out at 72 °C for 10 min. HPV genotypes were identified based on the methods employed. The following 41 HPV genotypes could be identified: 6, 11, 16, 18, 26, 30, 31, 32, 33, 35, 39, 40, 42, 43, 44, 45, 51, 52, 53, 54, 55, 56, 58, 59, 61, 62, 66, 67, 68, 69, 70, 71, 72, 73, 74, 81, 82, 83, 84, 87 and 99. Twelve HPV genotypes (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58 and 59) were classified as being high risk and 29 (6, 11, 26, 30, 32, 40, 42, 43, 44, 53, 54, 55, 61, 62, 66, 67, 68, 69, 70, 71, 72, 73, 74, 81, 82, 83, 84, 87 and 99) as being low risk. The HPV positivity rate in this study was defined as the presence of at least one positive result among the 41 HPV genotypes, irrespective of the specific genotype detected.

2.2 Procedure

The sample selection process for data collection is illustrated in Fig. 1. Of the 32,565 HPV specimens tested between January 2020 and June 2023, we excluded cases with insufficient information on sex (n = 417) or age (n = 194), those with data entry errors in age (n = 79), those without a personal identification number (n = 85), and those with a missing HPV genotype (n = 1).

The study was restricted to samples from adult men and excluded samples from women (n = 16,795). The total number of samples included in this study was 14,994.

Fig. 1.Sample selection process for data collection. ID, identification.

2.3 Data analysis

All statistical analyses were performed using SAS software (version 9.4, SAS Institute, Cary, NC, USA), Excel for Microsoft 365 MSO (version 2308, Microsoft, Redmond, WA, USA), and RStudio (version 2023.06.1, Posit, PBC, Boston, MA, USA). Nominal data such as HPV positivity rates are presented as frequencies and percentages, and differences in positivity rates were analyzed using the chi-squared test. Continuous data such as age are presented as means and standard deviations. Differences in means were analyzed by one-way analysis of variance. Statistical significance was set at p-values < 0.05.

3.1 Number of HPV infections and testing types

The infection rate was 62.9%, with the remaining 37.1% of patients not presenting evidence of infection. The maximum number of simultaneous co-infections was 10, reported in one person. The majority of samples (57.6%) exhibited single-type infection. Dual-type co-infections accounted for 25.1% of the positive samples; co-infections with three genotypes, for 10.9%; and co-infections with four or more genotypes, for 6.3%. Tissue samples and swabs accounted for the majority of the samples (Table 1).

3.2 Positivity rates for HPV infection according to age

Table 2 illustrates age-specific positivity rates for HPV infection by specimen. The overall HPV positivity rate was 62.9%, consistently exceeding 50% across all age groups. The highest positivity rate was observed in individuals in their 50s (69.6%), whereas the lowest was observed in teenagers (54.5%). For almost all age groups (except individuals in their 70s), single infections were significantly more common than co-infections (χ² = 81.502, p < 0.0001).

Among the specimens, the highest positivity rate for swabs was in the group of men in their 50s (62.6%), while the lowest was in the group of men 19 years old and younger (42.7%). The group with the highest number of single infections was men in their 60s (69.1%), and the highest number of multiple infections was seen in the group of men in their 70s and older (66.7%). For tissues, the highest positivity rate was among those aged 19 years and younger (94.6%), while the lowest positivity rate was among those aged 70 years and older (77.8%). For urine, the highest positivity rate was among those aged 19 years and younger (28.6%), and the lowest was among those aged 70 years and older (0%), but this group only had two specimens.

3.3 Rates of single and multiple HPV infections

Rates of single and multiple HPV infections in men were 57.6% and 42.4%, respectively. When examining multiple HPV infections in men across all age groups, the highest rate was found in men aged ≥70 years (13, 68.4%), although the sample size was limited.

3.4 Age-specific HPV co-infections

Examining age-specific concurrent HPV infections in men revealed that dual infections with two viruses were most prevalent in those in their 30s, whereas infections with three or more viruses concurrently were most common in individuals aged ≥70 years.

3.5 Genotypes and average ages of HPV-positive men

The mean age of HPV-positive men was 33.3 years, with a standard deviation of ±9.0 years. Fig. 2 presents the genotypes and average ages of HPV-positive Korean men. Excluding the age of individuals infected with genotype 69 (45.3 ± 15.5 years), the average age of individuals infected with HPV ranged from 30.4 ± 7.9 years (type 18, high risk) to 37.6 ± 11.0 years (type 32). The highest mean age corresponded to individuals infected with genotype 69 (F = 7.38, p < 0.0001).

Fig. 2.Average ages of HPV-positive men according to HPV genotype (N = 9428). HPV, Human papillomavirus.

Further details of each specimen are provided in Supplementary Table 1, which shows the mean age of HPV-positive men by genotype and specimen. For swabs, patients with genotype 69 had the highest mean age (45.9 ± 0.0 years). For tissue samples, patients with genotype 32 had the highest mean age (36.9 ± 9.3 years), and for urine samples, patients with genotype 54 had the highest mean age (48.0 ± 18.7 years).

3.6 Age-specific positivity rates of high-risk HPV infection according to genotype

Fig. 3 illustrates age-specific positivity rates of high-risk HPV infection according to genotype. The positivity rate for genotype 16 increased with age (χ² = 1012.028, p < 0.0001). The positivity rates for all genotypes varied with age, decreasing in diversity with increasing age.

Further details on each specimen are presented in Supplementary Table 2.

Fig. 3.Age-specific positivity rates of high-risk HPV infection according to genotype (N = 9428).

4.1 Implications for clinical practice

In this study, men showed a high positivity rate of HPV infection across all age ranges. This represents a risk to their sexual partners in terms of increased risk of transmission and potential health implications. Therefore, efforts should be directed toward proactive prevention and control of infections, including those among non-heterosexual individuals. Additionally, there should be an increase in awareness, promotion of vaccination, and implementation of public education programs covering HPV, including those targeted at adolescents. By focusing efforts on all genders, these initiatives aim to reduce the disease burden and transmission risk, ultimately contributing to the prevention of cervical cancer [25, 26].

4.2 Study strengths

The strength of our study lies in the use of a large-scale participant-based dataset encompassing individuals from their teenage years to their 70s.

4.3 Limitations and scope for future studies

This study was constrained by limited data (restricted to sex, age and sample results) and lacked additional information on clinical symptoms or underlying conditions of the participants. Furthermore, samples used in this study included swabs and tissue and urine samples. The absence of a direct comparison between sample categories and adjustments for each sample type in comparison with other studies may impose limitations to the interpretation of the results and analyses. As the samples were mainly from patients who had visited the clinic due to a suspected STIs, it is not possible to assume that all the samples are representative of those from a population of healthy men.