Relationship between cigarette smoking and human papilloma virus types 16 and 18 DNA load

Background: Although cigarette smoking has been associated with increased human papilloma virus (HPV) detection, its impact on HPV DNA load is unknown. Methods: The study subjects were women who were positive for HPV16 and/or HPV18 at enrollment into the Atypical Squamous Cells of Undetermined Significance - Low-grade Squamous Intraepithelial Lesion Triage Study. Assessments of exposure to smoke and sexual behavior were based on self-report. Viral genome copies per nanogram of cellular DNA were measured by multiplex real-time PCR. Linear or logistic regression models were used to assess the relationship between cigarette smoking and baseline viral load. Results: Of the 1,050 women (752 with HPV16, 258 with HPV18, and 40 with both HPV16 and HPV18), 452 (43.0%) were current smokers and 101 (9.6%) were former smokers at enrollment. The baseline viral load was statistically significantly greater for current compared with never smokers (P = 0.03 for HPV16; P = 0.02 for HPV18) but not for former smokers. Among current smokers, neither HPV16 nor HPV18 DNA load seemed to vary appreciably by age at smoking initiation, smoking intensity, or smoking duration. The results remained similar when the analysis of smoking-related HPV16 DNA load was restricted to women without detectable cervical abnormality. Conclusion: Higher baseline HPV16 and HPV18 DNA load was associated with status as a current but not former smoker. A lack of dose-response relationship between cigarette smoking and viral load may indicate a low threshold for the effect of smoking on HPV DNA load.