Risk factors associated with TB incidence in an adult population from poorly resourced South African urban communities with a high TB prevalence

Abstract

Introduction: Tuberculosis (TB) persists as a serious global public heath problem of a magnitude requiring urgent attention. The increase in new cases of TB in African countries where the prevalence of HIV is relatively low has been associated with other host and environmental factors. There is little or no comparable data on the association between host and environmental related factors and TB incidence in low HIV prevalence regions of South Africa. Objectives: This study aims to investigate host and environmental factors associated with incident TB in one region of South Africa. Methods: 3493 TB-free participants were recruited, and baseline data collected at the beginning of 2003 in the Lung Health Study in Ravensmead and Uitsig, Cape Town, South Africa. The TB register was used to identify new cases among the 3493 participants between 2003 and 2007. Results: Of the 3493 study participants, 109 developed TB; i.e. 57 males and 52 females. The incidence of TB in the Ravensmead and Uitsig study population was 632 per 100 000. Cohabiting, OR= 2.09 (95% CI= 1.05 - 4.17), smoking, OR= 2.19 (95% CI= 1.48 - 4.14), and history of imprisonment OR= 1.88 (95% CI= 1.09 - 3.23) were all statistically associated with TB incidence in multiple logistic regression models. The summary population attributable fraction for these three factors was 53.2%. Conclusions: TB incidence was high in this community. Cigarette smoking was one of the most important predictors of TB incidence, and the proportion of smokers in this population was relatively high. TB control and prevention strategies need to focus on interventions which will reduce or limit the impact of TB risk factors.