Table 5 Summary of results to evaluate the causal association between smoking and tooth loss
From: Causal assessment of smoking and tooth loss: A systematic review of observational studies
Element | Description for consistency and study type | Evaluation of consistency | Evaluation of study type | Perceived shortcoming |
|---|---|---|---|---|
Strength of association | All studies reported significant associations based on effect size: moderate association in 5 CSSs, 1 PCS and 1 CSS for males; weak association in 1 PCS and 1 CSS for females. | Evidence for weak or moderate association based on effect size is strong. | Evidence for strength of association is convincing. | Not applicable |
Natural experiment | All studies reported smaller effect size in former smokers than in current smokers. The association between former smoking and tooth loss relative to non-smokers was not significant in 3 CSSs and 1 PCS, and was significant in 3 CSSs and 1 PCS. The description of association in former vs. current smokers decreased in 4 CSSs, 2 PCSs and 1 CSS for males, and remained at the same level in 1 CSS and 1 CSS for females. The hazard ratio decreased based on years of abstinence in 2 PCSs. | Evidence for natural experiment is strong. However, this interpretation does not mean that the risk in former smokers is lesser than that in current smokers. | Evidence for natural experiment is probable. | Control group did not comprise current smokers, and only a relative relationship was evaluated. |
Dose-response relationship | Trend of the relationship between level of exposure and effect size, i.e. odds ratio or hazard ratio, was obvious in 3 CSSs and 1 PCS. This trend was highly significant in 2 CSSs. | Evidence for the dose-response relationship is strong. This interpretation is limited to populations assessed in 3 countries. | Evidence for dose-response relationship is probable. | Findings pertain to limited populations and 1 PCS. |