Background: Diabetes and metabolic syndrome have been found to increase the risk of various cancers. Previous studies indicated that diabetes may increase the risk of head and neck squamous cell carcinoma (HNSCC). Metabolic syndrome has not been investigated as a risk factor. We tested whether type II diabetes or metabolic syndrome were associated with HNSCC using a very large database of medical administrative records, providing the ability to investigate relatively weak effects and stratify by subgroups.
Methods: We identified persons diagnosed with HNSCC between 1994 and 2007 in the Surveillance, Epidemiology, and End Results (SEER)-Medicare database. We selected controls from a 5% sample of Medicare beneficiaries and frequency matched to cases on sex and duration of enrollment. We estimated odds ratios (OR) and 95% confidence intervals (CI) for the association between type II diabetes/metabolic syndrome and HNSCC, adjusted for potential confounders, among 14,022 cases and 42,066 controls.
Results: We observed a very weak inverse association between type II diabetes and HNSCC (OR=0.92; 95% CI, 0.88-0.96) and a moderate inverse association for metabolic syndrome (OR=0.81; 95% CI, 0.78-0.85). Associations were modified by tobacco use, with null results for type II diabetes among never users (OR=1.00; 95% CI, 0.95-1.06) and inverse associations among ever users (OR=0.80; 95% CI, 0.75-0.86).
Conclusions: We observed moderate inverse associations between metabolic syndrome and HNSCC and weak inverse associations between type II diabetes and HNSCC, which was contrary to the evidence to date. Inadequate control for confounding factors, such as overweight/obesity, may have influenced results.
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