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Problem drinking as a risk factor for tuberculosis: a propensity score matched analysis of a national survey.

Cois A, Ehrlich R - BMC Public Health (2013)

Bottom Line: A propensity score approach was used to match each problem drinker in the sample with a subset of moderate drinkers/abstainers with similar characteristics in respect to a set of potential confounders.Sensitivity analyses were conducted to assess the robustness of the results in respect to misspecification of the model.Within the limitations of a cross-sectional study design with self-reported tuberculosis status, these results adds to previous evidence of a causal link between problem drinking and tuberculosis, and suggest that the observed higher prevalence of tuberculosis among problem drinkers commonly found in population studies cannot be attributed to the confounding effect of the uneven distribution of other risk factors.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Public Health and Family Medicine, University of Cape Town, Anzio Road, Observatory 7925, Cape Town, South Africa. Annibale.Cois@uct.ac.za.

ABSTRACT

Background: Epidemiological and other evidence strongly supports the hypothesis that problem drinking is causally related to the incidence of active tuberculosis and the worsening of the disease course. The presence of a large number of potential confounders, however, complicates the assessment of the actual size of this causal effect, leaving room for a substantial amount of bias. This study aims to contribute to the understanding of the role of confounding in the observed association between problem drinking and tuberculosis, assessing the effect of the adjustment for a relatively large number of potential confounders on the estimated prevalence odds ratio of tuberculosis among problem drinkers vs. moderate drinkers/abstainers in a cross-sectional, nationally representative sample of the South African adult population.

Methods: A propensity score approach was used to match each problem drinker in the sample with a subset of moderate drinkers/abstainers with similar characteristics in respect to a set of potential confounders. The prevalence odds ratio of tuberculosis between the matched groups was then calculated using conditional logistic regression. Sensitivity analyses were conducted to assess the robustness of the results in respect to misspecification of the model.

Results: The prevalence odds ratio of tuberculosis between problem drinkers and moderate drinkers/abstainers was 1.97 (95% CI: 1.40 to 2.77), and the result was robust with respect to the matching procedure as well as to incorrect adjustment for potential mediators and to the possible presence of unmeasured confounders. Sub-population analysis did not provide noteworthy evidence for the presence of interaction between problem drinking and the observed confounders.

Conclusion: In a cross-sectional national survey of the adult population of a middle income country with high tuberculosis burden, problem drinking was associated with a two fold increase in the odds of past TB diagnosis after controlling for a large number of socio-economic and biological confounders. Within the limitations of a cross-sectional study design with self-reported tuberculosis status, these results adds to previous evidence of a causal link between problem drinking and tuberculosis, and suggest that the observed higher prevalence of tuberculosis among problem drinkers commonly found in population studies cannot be attributed to the confounding effect of the uneven distribution of other risk factors.

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Standardised percent bias in the distribution of potential confounders of the association between problem drinking and TB in the South-African adult population. Pre- and post-matching differences in the prevalence of each potential confounder between problem drinkers and moderate drinkers/abstainers as a percentage of the square root of the average of their variances. For definition of variables, see text.
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Figure 1: Standardised percent bias in the distribution of potential confounders of the association between problem drinking and TB in the South-African adult population. Pre- and post-matching differences in the prevalence of each potential confounder between problem drinkers and moderate drinkers/abstainers as a percentage of the square root of the average of their variances. For definition of variables, see text.

Mentions: The matching procedure was effective in creating a group of unexposed subjects comparable to the group of problem drinkers in respect of all observed confounders. Before matching, the distribution of potential confounders was very different between exposed and unexposed, while the matched groups showed only a slight residual imbalance, with values of standardised bias ≤ 3.5% across all variables, down from the pre-matching maximum of 105% (Figure1). None of the post-matching differences between groups were statistically significant (t-test for difference in means, p > 0.4). Distribution of PS were also almost completely overlapped after matching (Figure2).


Problem drinking as a risk factor for tuberculosis: a propensity score matched analysis of a national survey.

Cois A, Ehrlich R - BMC Public Health (2013)

Standardised percent bias in the distribution of potential confounders of the association between problem drinking and TB in the South-African adult population. Pre- and post-matching differences in the prevalence of each potential confounder between problem drinkers and moderate drinkers/abstainers as a percentage of the square root of the average of their variances. For definition of variables, see text.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3852702&req=5

Figure 1: Standardised percent bias in the distribution of potential confounders of the association between problem drinking and TB in the South-African adult population. Pre- and post-matching differences in the prevalence of each potential confounder between problem drinkers and moderate drinkers/abstainers as a percentage of the square root of the average of their variances. For definition of variables, see text.
Mentions: The matching procedure was effective in creating a group of unexposed subjects comparable to the group of problem drinkers in respect of all observed confounders. Before matching, the distribution of potential confounders was very different between exposed and unexposed, while the matched groups showed only a slight residual imbalance, with values of standardised bias ≤ 3.5% across all variables, down from the pre-matching maximum of 105% (Figure1). None of the post-matching differences between groups were statistically significant (t-test for difference in means, p > 0.4). Distribution of PS were also almost completely overlapped after matching (Figure2).

Bottom Line: A propensity score approach was used to match each problem drinker in the sample with a subset of moderate drinkers/abstainers with similar characteristics in respect to a set of potential confounders.Sensitivity analyses were conducted to assess the robustness of the results in respect to misspecification of the model.Within the limitations of a cross-sectional study design with self-reported tuberculosis status, these results adds to previous evidence of a causal link between problem drinking and tuberculosis, and suggest that the observed higher prevalence of tuberculosis among problem drinkers commonly found in population studies cannot be attributed to the confounding effect of the uneven distribution of other risk factors.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Public Health and Family Medicine, University of Cape Town, Anzio Road, Observatory 7925, Cape Town, South Africa. Annibale.Cois@uct.ac.za.

ABSTRACT

Background: Epidemiological and other evidence strongly supports the hypothesis that problem drinking is causally related to the incidence of active tuberculosis and the worsening of the disease course. The presence of a large number of potential confounders, however, complicates the assessment of the actual size of this causal effect, leaving room for a substantial amount of bias. This study aims to contribute to the understanding of the role of confounding in the observed association between problem drinking and tuberculosis, assessing the effect of the adjustment for a relatively large number of potential confounders on the estimated prevalence odds ratio of tuberculosis among problem drinkers vs. moderate drinkers/abstainers in a cross-sectional, nationally representative sample of the South African adult population.

Methods: A propensity score approach was used to match each problem drinker in the sample with a subset of moderate drinkers/abstainers with similar characteristics in respect to a set of potential confounders. The prevalence odds ratio of tuberculosis between the matched groups was then calculated using conditional logistic regression. Sensitivity analyses were conducted to assess the robustness of the results in respect to misspecification of the model.

Results: The prevalence odds ratio of tuberculosis between problem drinkers and moderate drinkers/abstainers was 1.97 (95% CI: 1.40 to 2.77), and the result was robust with respect to the matching procedure as well as to incorrect adjustment for potential mediators and to the possible presence of unmeasured confounders. Sub-population analysis did not provide noteworthy evidence for the presence of interaction between problem drinking and the observed confounders.

Conclusion: In a cross-sectional national survey of the adult population of a middle income country with high tuberculosis burden, problem drinking was associated with a two fold increase in the odds of past TB diagnosis after controlling for a large number of socio-economic and biological confounders. Within the limitations of a cross-sectional study design with self-reported tuberculosis status, these results adds to previous evidence of a causal link between problem drinking and tuberculosis, and suggest that the observed higher prevalence of tuberculosis among problem drinkers commonly found in population studies cannot be attributed to the confounding effect of the uneven distribution of other risk factors.

Show MeSH
Related in: MedlinePlus