Dietary Glycemic Index, Glycemic Load, and Risk of Lung Cancer: A Population-Based Cohort Study.

BACKGROUND: There is considerable inconsistency regarding study results on the association of dietary glycemic index (GI) and glycemic load (GL) with lung cancer risk. We aimed to investigate this relation in the US National Cancer Institute's Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial cohort. METHODS: Baseline characteristics were collected with the baseline questionnaire, and diet was assessed with the diet history questionnaire. All incident lung cancer cases were verified via pathology. We estimated hazard ratios (HRs) and 95% CIs for lung cancer risk associated with GI and GL by Cox regression modeling. RESULTS: During a median follow-up of 12.2 years (1,213,533 person-years), a total of 1,706 incident lung cancer events occurred including 1,473 (86.3%) cases of non-small cell lung cancer (NSCLC) and 233 (13.7%) of small cell lung cancer (SCLC). After multivariate adjustment, GI was positively associated with lung cancer (4th quartile [Q4] vs 1st quartile [Q1]; HR 1.13; 95% CI, 1.05-1.31), NSCLC (Q4 vs Q1; HR 1.11; 95% CI, 1.05-1.29), and SCLC (Q4 vs Q1; HR 1.34; 95% CI, 1.02-2.27). Conversely, we found an association between dietary GL and a decreased risk of lung cancer (Q4 vs Q1; HR 0.72; 95% CI, 0.57-0.90) and NSCLC (Q4 vs Q1; HR 0.68; 95% CI, 0.53-0.87) but not SCLC (Q4 vs Q1; HR 0.90; 95% CI, 0.51-1.58). These results were consistently observed across subgroup analyses. CONCLUSIONS: These findings show that high dietary GI is associated with an increased risk of lung cancer, NSCLC, and SCLC, whereas GL is inversely associated with the risk of lung cancer and NSCLC.