Introduction: The purpose of this case-control study was to determine whether smoking plays a role in tuberculin skin test conversion among the inmate population of South Carolina.
Results: The major findings of this study indicate that smokers were more likely to have become tuberculin skin test converters during incarceration than nonsmokers (odds ratio [OR] = 1.78, 95% confidence intervals [CI = 0.98, 3.21). Inmates who smoked 1 to 20 cigarettes per day prior to incarceration (OR = 1.32, 95% CI = 0.76, 2.31), and those who smoked > 20 cigarettes per day prior to incarceration (OR = 1.75, 95% CI = 0.83, 3.71) were more likely to have become converters during incarceration than nonsmokers, suggesting a dose-response effect. Converters were found to have reduced their number of cigarettes smoked per day since incarceration. Those inmates smoking 1 to 10 cigarettes per day (OR = 1.88, 95% CI = 0.96, 3.69), and those who smoked > 10 cigarettes per day since incarceration (OR = 1.87, 95% CI = 0.92, 3.78) were more likely to have become converters than nonsmokers. Interestingly, inmates who smoked for 15 years or less were more likely to have become tuberculin skin test converters than nonsmokers (OR = 1.60, 95% CI = 0.81, 3.16), while those smoking for more than 15 years were more likely to have become converters than nonsmokers while incarcerated (OR = 2.12, 95% CI = 1.03, 4.36).
Conclusions: This suggests that the cumulative effects related to the duration of smoking may be more important than the number of cigarettes smoked with regard to tuberculin skin test conversion. This is consistent with the understanding that long-term exposure to cigarette smoking has an adverse effect on the lung's defense mechanisms, namely mucociliary clearance of potential pathogens, such as Mycobacterium tuberculosis.