Cervical cancer is the fourth most common cancer in women worldwide. High-risk oncogenic human papillomavirus (HPV) types, mostly HPV 16 and 18 are the causative agents of cervical cancer. HPV infection is sexually transmitted. However, most HPV infections are transient and only few of them persist. Therefore, HPV infection alone is not sufficient for causing cancer. Other sexually associated co-factors such as number of sexual partners, use of hormonal contraceptives, early age of sexual onset, the presence of other sexually transmitted infections – most notably the Chlamydia trachomatis infection – and smoking are found to increase the risk of cervical neoplasia.
In a cohort of participants from a randomised trial of HPV16/18 vaccine efficacy and a cluster randomised trial on the effectiveness of different HPV vaccination strategies, we studied how oral contraceptives and sexual behaviours influence the risk of cervical neoplasia, a precursor of invasive cervical cancer. The duration of oral contraceptive use and the risk of oncogenic HPV infection were also studied in a sample from the Finnish Student Health Service (FSHS) and the Finnish Maternity Cohort (FMC) serum bank.
The long-term use of oral contraceptives was associated with HPV seropositivity. The long duration of oral contraceptive use and the presence of C. trachomatis infection together were associated with an increased risk of squamous intraepithelial lesions, which are precursors of cervical cancer. Our study also found that the C. trachomatis infection occurs as soon as a person is sexually active and is associated with cervical pre-cancerous lesions.
Thus, sexual health education at school should focus on having fewer sexual partners, using barrier methods in addition to oral contraceptives, delaying the age of the first sexual encounter, being aware of the symptoms of sexually transmitted infections, and lowering the threshold of C. trachomatis screening. When providing free contraception to adolescents, health care professionals should also provide sexual health counselling.
The doctoral dissertation of MSc (Public health) Indira Adhikari titled Association of Sexual Behaviour and Oral Contraceptive Use with Cervical Neoplasia, supervised by Docent Matti Lehtinen will be publicly examined in the Faculty of Social Sciences at Tampere University on Friday 9 December 2022 from 12 noon in the auditorium F114 of the Arvo building. Professor Oskari Heikinheimo from the University of Helsinki acts as the opponent. The Custos will be Professor Pekka Nuorti from the Faculty of Social Sciences.
Photo: Deependra Singh