Characteristics of studies included in the meta-analysis.

a<p>Some controls were shared. PCR, polymerase chain reaction; Q-FISHLSC, quantitative fluorescence in situ hybridization-based approaches.</p

Flow chart for the process of selecting the final 21 publications.

<p>Flow chart for the process of selecting the final 21 publications.</p

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

a<p>Some controls in the publication by Wu (2003) <i>et al</i> 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) <i>et al</i> was family-based and excluded from the analysis for source of controls.</p>b<p>Random effects model.</p>c<p>Fixed effects model.</p

Odds ratios (ORs) and 95% confidence intervals (CIs) for risk of different cancers associated with relative telomere length (shorter <i>vs.</i> longer, grouped by median value of telomere length ratio).

<p>(<b>A</b>) Smoking-related cancers; (<b>B</b>) Cancers in the digestive system; (<b>C</b>) Cancers in the urogenital system.</p

Funnel plot analysis to detect publication bias.

<p>Each point represents an independent study for the indicated association.</p

Telomere length and risk of lung cancer: results for overall study and stratifying by years from enrollment to case diagnosis.

†<p>Telomere length categorized using tertiles in controls as cut-points.</p>*<p>N_Co indicates number of controls; and N_Ca, number of cases.</p>£<p>Odds ratios computed using conditional logistic regression adjusted for age and ever smoking.</p>‡<p>P trend calculated by using log transformed telomere length as continuous variable, adjusted for age and ever smoking.</p

Mean telomere length in association with rs2736100 (<i>CLPTM1L-TERT</i>), by case-control status in the Shanghai Women’s Health Study^*(All cases and controls).

*<p>log transformed telomere length as continuous variable was used.</p>‡<p>mean (SD).</p>†<p>P for trend calculated by using linear regression and rs2736100 by assigning the ordinal values 1, 2, and 3 for TT, GT, and GG respectively, adjusted for age and ever smoking.</p>£<p>P value from spearman correlation test.</p

Selected characteristic of lung cancer cases and individually matched controls selected from the Shanghai Women’s Health Study (recruited between 1997–2000).

$<p>Spearman correlation (r) with telomere length in controls is −0.41(P<0.0001).</p>£<p>P value of spearman r with telomere length in controls >0.05.</p>‡<p>Family history of lung cancer in first degree relatives.</p>*<p>NOS indicates not otherwise specified.</p>†<p>NA indicates not available.</p>††<p>NA indicates not available, as only never-smoking subjects were genotyped.</p