Cigarette smoking among tuberculosis patients increases risk of transmission to child contacts

Observational cohort study in Lima, Peru.

To determine the association between exposure to a smoking tuberculosis (TB) case and latent tuberculous infection (LTBI).

Between September 2009 and August 2012, we identified 2132 patients with drug-susceptible TB and their 2054 child household contacts. Data were collected on active and secondhand smoking status and other risk factors for infection specific to the index case, the household and the exposed contacts. Contacts underwent a tuberculin skin test (TST) to determine their tuberculous infection status at baseline, 6-month and 12-month follow-up. We estimated the association between exposure to a smoking index case and LTBI using a modified Poisson regression model.

The 21 children (age ⩿15 years) exposed to smoking index TB patients were more likely to be TST-positive at baseline (RR 2.64, 95%CI 1.78-3.91), by 6 months (RR 1.91, 95%CI 1.40-2.60) and by 12 months (RR 1.48, 95%CI 1.07-2.06), than those who were not exposed. TST positivity among children at these time points did not vary with secondhand smoke exposure.

TB patients who smoke may be more likely to transmit infection to their contacts. Interventions designed to reduce smoking among TB patients may minimise further spread of the disease.