Associations between relative telomere length and cancer risk stratified by selected factors.

aSome controls in the publication by Wu (2003) et al were shared by different cancers; therefore, it was defined as four studies (head and neck cancer, bladder cancer, lung cancer and renal cell carcinoma) in the analysis stratified by tumor type, but defined as one study in the analysis stratified by study type, ethnicity and source of controls. In addition, the publication by Shen (2007) et al was family-based and excluded from the analysis for source of controls.bRandom effects model.cFixed effects model.