Leptin is associated with an increased female colorectal cancer risk: a nested case-control study in Japan

OBJECTIVE: To elucidate whether leptin is involved in the etiology of female colorectal cancer. METHODS: A case-control study nested in the Japan Collaborative Cohort Study. We compared serum leptin levels in 58 cases of female colorectal cancer with those in 145 controls matched for study area and age. Data were analyzed using a conditional logistic regression model with adjustments for known risk factors for the development of colorectal cancer. Quintile cutoff points were determined on the distribution of leptin levels in cases and controls combined. RESULTS: Serum geometric mean levels of leptin were 6.88 ng/ml in cases and 6.00 ng/ml in controls. The odds ratios of female colorectal cancer risk were 1.40 (95% confidence interval, CI: 0.41-4.78) for the category of the second and third quintiles combined, and 4.84 (CI: 1.29-18.1) for the category of the fourth and fifth quintiles combined relative to the first quintile after adjustment for body mass index (BMI), life-style factors, reproductive factors, and hormonal variables including insulin-like growth factor and its binding protein. CONCLUSION: Our results suggest that leptin most likely increases the risk of female colorectal cancer substantially independent of BMI.