HIV-positive women who smoke have a significantly higher prevalence and incidence of human papilloma virus (HPV) in the cervix than HIV-positive non-smoking women, according to a US study published in the May 15th edition of the Journal of Infectious Diseases. The study investigators believe that smoking alters the natural history of HPV infection, therefore increasing the risk of cervical disease.
Earlier studies have shown a causal relationship between smoking and HPV prevalence and incidence in women. However, there have been questions about the methodology of these studies, and the studies have focused on HIV-negative women.
Accordingly, investigators from the US Women’s Interagency HIV Study (WIHS), a prospective study of the natural history of HPV infection involving HIV-positive women and women at risk of HIV, conducted a longitudinal study into the relationship between smoking and HPV infection. The investigators looked at HPV prevalence at baseline, incident HPV infections, and clearance of HPV infection.
A total of 1797 HIV-positive women and 496 at-risk women were recruited to the study between 1994 and 1997. At baseline and at six-monthly intervals, the women were given a physical examination to check for HPV lesions, a cervicovaginal lavage to collect samples for HPV DNA testing, and were asked about their smoking behaviour.
The investigators found that there were significant differences between individuals who were current or former smokers, and women who had never smoked, regardless of HIV status. Smokers were almost two years younger when they first had sexual intercourse (p=0.01), and had a higher number of mean sexual partners in the previous five years (p=0.01).
HIV-positive women were three times more likely than HIV-negative women to be infected with HPV at baseline (p<0.001). A positive relationship was also established between HPV infection at baseline and smoking and HIV infection (p=0.002). The investigators further found that, amongst HIV-positive women, smokers were more likely to be infected at baseline with an HPV genotype associated with a higher risk of cervical cancer (HPV genotype 16, OR 1.44, p=0.47, and HPV genotype 18 OR 2.45, p=0.001).
Adjusting for factors including age, sexual behaviour, CD4 cell count, viral load, and the use of HIV treatments, the investigators found that smoking independently and significantly increased the risk of an incident HPV infection in HIV-positive women (OR 1.33, 95% CI, 1.10-1.60, p=0.003). Furthermore, the investigators found that HIV-positive women who smoked were significantly more likely than HIV-positive non-smokers to have an incident infection with the high-risk HPV genotype 16 (risk hazard, 1.81, p=0.02).
HPV infection was also found to be significantly more likely to persist in HIV-positive women compared to HIV-negative women (OR 5.63, 95% CI, 3.38-9.35, p=0.001), and in smokers versus non-smokers (OR, 1.39, 95% CI, 1.05-1.86, p=0.02). However, the investigators did not find that HIV-positive smokers were significantly more likely to have a persistent infection.
The investigators comment, “we found that smoking is associated with a significantly higher incidence and prevalence of HPV infection among HIV-infected women.” They believe that this could be because smoking is immunosuppressive and can disrupt both systemic and mucosal immunity, and acts in synergy with HIV. They conclude, “smoking and HIV infections in conjunction may alter the natural history of HPV infection and thereby increase the risk of cervical disease… these data add to the litany of reasons for making smoking cessation a cornerstone of women’s health.”
Further information on this website
Human papilloma virus - overview
Smoking - factors affecting disease progression
Minkoff H et al. Relationship between smoking and human papillomavirus infections in HIV-infected and -uninfected women. Journal of Infectious Diseases, 189: 1821-1828, 2004.