It has long been known that alcohol consumption is associated with a risk of developing tuberculosis. The prevalence of alcohol-related disorders in patients with tuberculosis ranges from 10 to 50%. Studies have also shown that people in populations with a high rate of alcohol use disorders have a higher risk of developing tuberculosis. However, it has not been established how exactly this link can be caused by other factors, namely the social factors associated with alcohol consumption, or its strength.

Mechanisms that explain the relationship between alcohol consumption and the risk of developing active TB can include specific social habits in people with alcohol-induced disorders that result in a higher risk of infection or weakened immunity, leading to a higher risk of clinical morbidity due to tuberculosis infection.. The latter can be caused by the direct toxic effects of alcohol on the immune system or by other concomitant alcohol-related illnesses.

The authors carried out a systematic review of the available literature on the relationship between alcohol consumption and the risk of developing tuberculosis, and identified 3 cohort studies and 18 case-control studies. Subsequently, these studies were divided into categories based on the determination of the degree of exposure to alcohol, the type of tuberculosis studied and taking into account factors that may affect the result obtained during the study (the so-called interfering factors).

The studies were initially divided into 3 categories according to the level of alcohol consumed. The low consumption categories (4 studies) corresponded to a consumption of less than 40 ml of alcohol per day. The heavy alcohol consumption categories (5 studies) corresponded to the consumption of more than 40 ml of alcohol per day. The third category included 6 studies in which the diagnosis of an alcohol-induced disorder was obtained from the patient's medical records. The degree of overall effect was determined for each subcategory of studies.

Among all the studies with a high level of alcohol consumption (40 ml or more per day) or in which patients had a clinical diagnosis of an alcohol-related disorder, the total relative risk of developing tuberculosis was 3.5 (95% confidence interval (CI) 2.01) -5.93). After excluding small studies due to presumed errors, the overall relative risk decreased to 2.94 (95% CI 1.89-4.59). The review authors suggested that the magnitude of the overall effect in studies with high alcohol consumption, where the infectious status of patients was monitored (risk ratio 4.21; 95% CI 2.73- 6,48), may indicate that the possible route by which alcohol acts as a risk factor is an increase in the transition rate from a form of latent infection to active tuberculosis. The total risk ratio among 4 studies in the low-alcohol category was 1.08 (95% CI 0.82-1.40).

The analyzes of the research subgroups, taking into account different types of interfering factors, did not reveal any significant differences in the results and did not explain the significant heterogeneity of the results obtained in the studies.

Thus, the risk of developing active tuberculosis has been mainly increased in people who consume more than 40 ml of alcohol per day and / or suffer from disorders due to alcohol consumption. The researchers concluded that this could be a consequence of both an increased risk of infection due to the specific social habits of addicts and an effect on the immune system of alcohol itself and the conditions caused by consumption. These data are important in creating a tuberculosis control strategy in general, especially in countries where high levels of tuberculosis can be caused by alcohol consumption.

The limitations of this study can be viewed as possible differences in the classification of alcohol consumption, an underestimation of alcohol consumption in a number of studies, and errors caused by different approaches to subject selection. for the formation of control groups in case-control studies.

Future studies on the relationship between alcohol consumption and the risk of developing TB should carefully assess both the potential interference factors and the relationship between alcohol consumption and other risk factors for developing TB. tuberculosis. Possible differences in the risks of developing pulmonary and extrapulmonary tuberculosis should also be assessed.