Article type
Year
Abstract
Background:Smoking is a prevalent public health problem in the worldwide. Most of the researches on smoking and human health have focused on the harmful effect of smoking. However, the phenomenon that smoking has a protective effect on some diseases has attracted the attention of some researchers, and many systematic reviews have been carried out.
Objective: To review and analyze the systematic reviews of the protective effect of tobacco smoking.
Methods: We searched PubMed, EMBASE, The Cochrane Library and Web of Science from the establishment of each database to September 2019 to collect published systematic reviews of the protective effect of smoking on any condition. We used the AMSTAR Ⅱ tool to assess methodological quality of included studies, and the GRADE method to assess the quality of evidence of main outcome indicators. We reported the effect sizes of the incidence of the studied condition between smokers and non-smokers with 95% confidence interval (CI) and heterogeneity.
Results: We included thirteen systematic reviews. Five reviews assessed Parkinson's disease: the risk ratio (RR) of the disease comparing smokers with non-smokers across ranged from 0.35 (95%CI: 0.26-0.47) to 0.80 (95%CI: 0.69-0.93). Two reviews were about preeclampsia, reporting effect sizes of RR 0.70 (95%CI: 0.67-0.73 for cohort studies)/OR 0.68 (95%CI: 0.57-0.81 for case-control studies) and RR 0.67 (95%CI: 0.60-0.75). In addition, we found reviews on Alzheimer's disease (OR=0.78 95%CI: 0.62-0.98), skin cancer (RR=0.72, 95%CI: 0.58-0.86 for melanoma in males, RR=0.94, 95%CI: 0.90-0.98, for basal cell carcinoma in males and females), endometrial cancer (RR=0.81 95%CI: 0.74-0.88 for cohort studies, OR=0.72, 95%CI: 0.66-0.79, for case-control studies), pterygium (RR=0.82, 95%CI: 0.69-0.97), celiac disease (OR=0.52 95%CI: 0.32-0.84), and human acute cognitive response (six indicators, Hedges' g ranging from 0.16, 95%CI: 0.02-0.31, to 0.44, 95%CI: 0.17-0.71). Five studies were of low methodological quality and eight of were very low methodological quality. For all 19 main outcome indicators, the quality of evidence was very low.
Conclusion: The available evidences suggest that smoking may have a protective effect against Parkinson's disease, preeclampsia, Alzheimer's disease, skin cancer, endometrial cancer, pterygium, celiac disease and acute cognitive response in humans. However, the overall quality of these studies is relatively low. There is no doubt that smoking does more harm than good. But figuring out the relevant protective mechanisms may be helpful in the treatment of these diseases. The exact mechanisms of the protective analysis are currently poorly understood and need further assessment.
Key words: Smoking; Systematic review; Meta-analysis
Patient or healthcare consumer involvement:none.
Objective: To review and analyze the systematic reviews of the protective effect of tobacco smoking.
Methods: We searched PubMed, EMBASE, The Cochrane Library and Web of Science from the establishment of each database to September 2019 to collect published systematic reviews of the protective effect of smoking on any condition. We used the AMSTAR Ⅱ tool to assess methodological quality of included studies, and the GRADE method to assess the quality of evidence of main outcome indicators. We reported the effect sizes of the incidence of the studied condition between smokers and non-smokers with 95% confidence interval (CI) and heterogeneity.
Results: We included thirteen systematic reviews. Five reviews assessed Parkinson's disease: the risk ratio (RR) of the disease comparing smokers with non-smokers across ranged from 0.35 (95%CI: 0.26-0.47) to 0.80 (95%CI: 0.69-0.93). Two reviews were about preeclampsia, reporting effect sizes of RR 0.70 (95%CI: 0.67-0.73 for cohort studies)/OR 0.68 (95%CI: 0.57-0.81 for case-control studies) and RR 0.67 (95%CI: 0.60-0.75). In addition, we found reviews on Alzheimer's disease (OR=0.78 95%CI: 0.62-0.98), skin cancer (RR=0.72, 95%CI: 0.58-0.86 for melanoma in males, RR=0.94, 95%CI: 0.90-0.98, for basal cell carcinoma in males and females), endometrial cancer (RR=0.81 95%CI: 0.74-0.88 for cohort studies, OR=0.72, 95%CI: 0.66-0.79, for case-control studies), pterygium (RR=0.82, 95%CI: 0.69-0.97), celiac disease (OR=0.52 95%CI: 0.32-0.84), and human acute cognitive response (six indicators, Hedges' g ranging from 0.16, 95%CI: 0.02-0.31, to 0.44, 95%CI: 0.17-0.71). Five studies were of low methodological quality and eight of were very low methodological quality. For all 19 main outcome indicators, the quality of evidence was very low.
Conclusion: The available evidences suggest that smoking may have a protective effect against Parkinson's disease, preeclampsia, Alzheimer's disease, skin cancer, endometrial cancer, pterygium, celiac disease and acute cognitive response in humans. However, the overall quality of these studies is relatively low. There is no doubt that smoking does more harm than good. But figuring out the relevant protective mechanisms may be helpful in the treatment of these diseases. The exact mechanisms of the protective analysis are currently poorly understood and need further assessment.
Key words: Smoking; Systematic review; Meta-analysis
Patient or healthcare consumer involvement:none.