Relation of the Metabolic Syndrome to Incident Colorectal Cancer in Young Adults Aged 20 to 49 Years

Onco-cardiology is the emerging field, and the concept of shared risk factor holds an important position in this field. The increasing prevalence of colorectal cancer (CRC) in young adults is a critical epidemiological issue. Although metabolic syndrome, which is a major risk factor for cardiovascular disease, is known to be associated with CRC incidence in middle-aged and elderly individuals, it is unclear whether this association is present in young adults. We assessed whether metabolic syndrome was associated with CRC events in young adults (aged50 years), and whether the association differed by the definition of metabolic syndrome. We retrospectively analyzed 902,599 adults (20 to 49 years of age) enrolled in the JMDC Claims Database which is a nationwide epidemiological database in Japan between January 2005 and August 2018. Participants who had a history of CRC, colorectal polyps, or inflammatory bowel disease were excluded. Study participants were categorized into 2 groups according to the presence of metabolic syndrome, defined using the Japanese criteria (waist circumference ≥85 cm for men and ≥90 cm for women, and ≥2 metabolic parameters including elevated blood pressure, elevated triglycerides, reduced high-density lipoprotein cholesterol, or elevated fasting plasma glucose). Clinical outcomes were collected between January 2005 and August 2018. The primary outcome was CRC of any stage. Median (interquartile range) age was 41 (37 to 45), and 55.4% were men. Over a median follow-up of 1,008 (429 to 1,833) days, there were 1,884 incidences of CRC. After multivariable adjustment, the hazard ratio (HR) of metabolic syndrome for CRC events was 1.26 (95% confidence interval [CI] = 1.07 to 1.49). Cox regression analysis after multiple imputation for missing values showed that metabolic syndrome was associated with CRC incidence (HR = 1.35, 95% CI = 1.17 to 1.56). Metabolic syndrome was also associated with a higher incidence of CRC in individuals with a follow-up period of ≥365 days (HR = 1.33, 95% CI = 1.10 to 1.60). This association was observed when metabolic syndrome was defined according to the International Diabetes Federation criteria (HR = 1.30, 95% CI = 1.09 to 1.55) and the National Cholesterol Education Program Adult Treatment Panel III criteria (HR = 1.39, 95% CI = 1.12 to 1.72). In conclusion, metabolic syndrome was associated with a higher incidence of CRC among individuals aged50 years. These results could be informative for risk stratification of subsequent CRC among young adults.