Relationship between cigarette smoking and risk of chronic myeloid leukaemia: a meta-analysis of epidemiological studies.
OBJECTIVE
Previous epidemiologic studies that have been reported on the association between cigarette smoking and risk of chronic myeloid leukaemia (CML) have remained controversial. A comprehensive meta-analysis was performed to evaluate smoking as a potential relationship factor and incidence of CML.


METHODS
Systematic literatures collected from articles published before August 2015 were searched from PubMed, EMBASE and the Cochrane Library. A total of 10 studies (nine case-controls and one cohort) met inclusion criteria of this meta-analysis. Odds ratios (ORs) with 95% confidence interval (CI) were calculated to assess the strength of the association between cigarette smoking and risk of CML in this study. Quality assessments were performed on the studies with the Newcastle-Ottawa Scale. I2 index was used to evaluate heterogeneity. Finally, publication bias was assessed through funnel plots and Begger's test.


RESULTS
No significant association was observed between ever-smokers and CML when compared among non-smokers (OR = 1.13, 95% CI: 0.99-1.29) or between subgroups stratified by smoking history, gender, geographical region, study design and source of patients. Our results demonstrate that this association was stronger in individuals who smoked <20 cigarettes/day (OR = 1.72, 95% CI: 1.06-2.79) vs. individuals who smoked >20 cigarettes/day (OR = 1.24, 95% CI: 0.55-2.81). Moreover, cumulative smoking of <15, 15-30 and >30 pack-years was associated with ORs of 1.22, 1.32 and 1.39, respectively (P < 0.001, for trend).


CONCLUSIONS
This meta-analysis suggests that smoking may significantly increase the risk of CML in a dose-dependent manner. However, additional well-designed, prospective cohort studies are required to verify these findings and identify other risk factors associated with CML.
a Department of Hematology, First Affiliated Hospital, College of Clinical Medicine , Henan University of Science and Technology , Luoyang , Henan , China.
Ling
L
Qin
a Department of Hematology, First Affiliated Hospital, College of Clinical Medicine , Henan University of Science and Technology , Luoyang , Henan , China.
Hui-Yang
HY
Deng
b Department of Ultrasound, First Affiliated Hospital, College of Clinical Medicine , Henan University of Science and Technology , Luoyang , Henan , China.
Sheng-Jiang
SJ
Chen
a Department of Hematology, First Affiliated Hospital, College of Clinical Medicine , Henan University of Science and Technology , Luoyang , Henan , China.
Wei
W
Wei
D016022:Case-Control Studies; D015331:Cohort Studies; D006801:Humans; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000453:epidemiology*; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology*
Chronic myeloid leukaemia; case–control/cohort study; cigarette smoking; epidemiology; meta-analysis; risk factors