The Comparison of Different Obesity Indexes and the Risk of Lung Cancer: A Meta-Analysis of Prospective Cohort Studies.

To evaluate the relationship between obesity, analyzed by different indicators, and lung cancer incidence, literature search was conducted in the PubMed, Web of Science, EBSCO, Ovid, and China National Knowledge Infrastructure databases for articles published until December 2018. Twenty-eight prospective cohort studies were identified, with 28 784,269 participants and 127,161 lung cancer cases were included in the analysis. The combined relative risks (RRs) with 95% CIs for the highest versus normal category of body mass index (BMI) were RR = 0.77 (95% CI: 0.72-0.82), but the inverse association disappeared for never smokers or small cell carcinoma after stratifying the smoking status or histological cancer types, respectively. Further analysis considered lag time and excluded the effects of preclinical cancer, there is no statistically significant inverse association between BMI and lung cancer risk, RR = 0.89 (95% CI: 0.66-1.19). In contrast, the combined RRs with 95% CIs for the highest versus lowest category of waist circumference (WC) were RR = 1.26 (95% CI: 1.14-1.39). Therefore, due to multiple confounders existed, BMI might not be an appropriate indicator for obesity when study lung cancer risk. The significantly positive relationship between WC and lung cancer risk indicated there might have an etiological connection between central obesity and lung cancer development.

Dietary Cholesterol Intake and Risk of Lung Cancer: A Meta-Analysis.

Multiple epidemiologic studies have evaluated the relationship between dietary cholesterol and lung cancer risk, but the association is controversial and inconclusive. A meta-analysis of case-control studies and cohort studies was conducted to evaluate the relationship between dietary cholesterol intake and lung cancer risk in this study. A relevant literature search up to October 2017 was performed in Web of Science, PubMed, China National Knowledge Infrastructure, Sinomed, and VIP Journal Integration Platform. Ten case-control studies and six cohort studies were included in the meta-analysis, and the risk estimates were pooled using either fixed or random effects models. The case-control studies with a total of 6894 lung cancer cases and 29,736 controls showed that dietary cholesterol intake was positively associated with lung cancer risk (Odds Ratio = 1.70, 95% Confidence Interval: 1.43-2.03). However, there was no evidence of an association between dietary cholesterol intake and risk of lung cancer among the 241,920 participants and 1769 lung cancer cases in the cohort studies (Relative Risk = 1.08, 95% Confidence Interval: 0.94-1.25). Due to inconsistent results from case-control and cohort studies, it is difficult to draw any conclusion regarding the effects of dietary cholesterol intake on lung cancer risk. Carefully designed and well-conducted cohort studies are needed to identify the association between dietary cholesterol and lung cancer risk.