Cancer risk according to fasting blood glucose trajectories: a population-based cohort study

BACKGROUND: Diabetes mellitus is known to increase the risk of cancer. Fasting blood glucose (FBG) levels can be changed over time. However, the association between FBG trajectory and cancer risk has been insufficiently studied. This research aims to examine the relationship between FBG trajectories and cancer risk in the Korean population. METHODS: We analyzed data from National Health Insurance Service-National Health Screening Cohort collected between 2002 and 2015. Group-based trajectory modeling was performed on 256,271 Koreans aged 40 to 79 who had participated in national health examinations at least three times from 2002 to 2007. After excluding patients with cancer history before 2008, we constructed a cancer-free cohort. The Cox proportional hazards model was applied to examine the association between FBG trajectories and cancer incidence, after adjusting covariates. Cancer case was defined as a person who was an outpatient thrice or was hospitalized once or more with a cancer diagnosis code within the first year of the claim. RESULTS: During the follow-up time (2008-2015), 18,991 cancer cases were identified. Four glucose trajectories were found: low-stable (mean of FBG at each wave <100 mg/dL), elevated-stable (113-124mg/dL), elevated-high (104-166mg/dL), and high-stable (>177mg/dL). The high-stable group had elevated risks in multiple myeloma, liver and gastrointestinal cancer, with hazard ratio (HR): 4.09 (95% confidence interval (CI): 1.40-11.95), HR: 1.68 (95%CI: 1.25-2.26) and HR: 1.27 (95%CI: 1.11-1.45) respectively. In elevated-stable group, the risk increased for all cancer (HR: 1.08, 95%CI: 1.02-1.16) and stomach cancer (HR: 1.24, 95%CI: 1.07-1.43). Significant associations were also found in the elevated-high group with oral (HR: 2.13, 95%CI: 1.01-4.47), liver (HR:1.50, 95%CI: 1.08-2.08) and pancreatic cancer (HR:1.99, 95%CI: 1.20-3.30). CONCLUSIONS: Our study highlights that the uncontrolled high glucose level for many years may increase cancer risk. KEY MESSAGES: • Individuals in the prediabetes stage may be at an increased risk of developing cancer. • Fasting blood glucose trajectories may be a predictive factor for the development of digestive cancer.