Abstract
Leisure sedentary behavior, especially television watching, has been previously reported as associated with the risk of lung cancer in observational studies. This study aims to evaluate the causal association with two-sample Mendelian randomization (MR) analysis. Single nucleotide polymorphisms associated with leisure television watching, computer use, and driving were extracted from genome-wide association studies. Summary-level results of lung cancer overall and histological types were obtained from International Lung Cancer Consortium (ILCCO). In univariable MR using inverse-variance-weighted method, we observed causal effects of television watching on lung cancer [OR, 1.89, 95% confidence interval (CI), 1.41, 2.54; p = 2.33 × 10−5], and squamous cell lung cancer (OR, 2.37, 95% CI, 1.58, 3.55; p = 3.02 × 10−5), but not on lung adenocarcinoma (OR, 1.40, 95% CI, 0.94, 2.09; p = 0.100). No causal effects of computer use and driving on lung cancer were observed. Television watching significantly increased the exposure to several common risk factors of lung cancer. The associations of television watching with lung cancer and squamous cell lung cancer were compromised after adjusting for smoking quantity with multivariable MR. Our mediation analyses estimated indirect effects of television watching on lung cancer (beta, 0.31, 95% CI, 0.13, 0.52; p = 6.64 × 10−4) and squamous cell lung cancer (beta, 0.33, 95% CI, 0.14, 0.53, p = 4.76 × 10−4) mediated by smoking quantity. Our findings indicate that television watching is positively correlated with the risk of lung cancer, potentially mediated through affecting smoking quantity.
Highlights
Nowadays people are more and more prone to extended sedentary behaviors in their daily life due to the increased time spent on television watching, computer use, and driving (Healy et al, 2011; Proper et al, 2011)
The odds ratios (ORs) were 1.89 [95% confidence interval (CI), 1.41, 2.54; p 2.33 × 10−5], 1.40, and 2.37 for lung cancer, lung adenocarcinoma, and squamous cell lung cancer respectively for 1 SD increase of television watching time (1.5 h) by using a inverse-variance weighted (IVW) method (Figure 1)
We analyzed the causal effect of leisure sedentary behaviors on two main histologic subtypes of lung cancer utilizing MR analyses
Summary
Nowadays people are more and more prone to extended sedentary behaviors in their daily life due to the increased time spent on television watching, computer use, and driving (Healy et al, 2011; Proper et al, 2011). Previous scientific evidence has shown that increased leisure sedentary behaviors are associated with a higher risk of all-cause mortality, incidence, and mortality of the cardiovascular disease, type 2 diabetes, and cancer (Physical Activity Guidelines Advisory Committee, 2018). The evidence that indicates the relationship between sedentary behavior and cancer has been graded as moderate, and there is limited evidence that suggests a direct link between sedentary behavior and incident lung cancer (Physical Activity Guidelines Advisory Committee, 2018). Leisure Sedentary and Lung Cancer publications have studied the associations between leisure sedentary behavior and lung cancer (Schmid and Leitzmann, 2014; Shen et al, 2014). Randomized controlled studies are unethical and inappropriate to be performed on this topic
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