In a recent study published in JAMA Network Open, Researchers determined the relationship between type 2 diabetes (T2D) and colorectal cancer (CRC) risk among low-income African Americans.
Study: Risk of type 2 diabetes and colon cancer. Image credit: Andrey_Popov / Shutterstock.com
Record
T2D and CRC disproportionately burden low-income African Americans. Metabolic dysregulations during diabetes could contribute to the growth and proliferation of CRC cells by increasing oxidative stress and inflammation.
CRC shares many factors that contribute to diabetes, including low economic status, smoking, obesity, and black race. However, modification of the relationship between diabetes and CRC risk by common risk factors, including socioeconomic status and race, has not been extensively explored.
About the study
The current study analyzed data from the Southern Community Cohort Study (SCCS) in the United States, which recruited people between 2002 and 2009. SCCS participants completed three survey-based follow-up assessments at five-year intervals through 2018.
Of 85,000 subjects, 86% were from community health care centers in 12 US states, and 14% were recruited by telephone or email contact. At enrollment, participants completed questionnaires on demographic parameters, family history of disease, medical history, physical activity, and diet.
Participants documented their race and age at diabetes diagnoses. CRC was diagnosed using the International Classification of Diseases (ICD)-Oncology third edition codes.
Individuals with more than two years of follow-up data, previous tumor diagnosis at intake, missing data on diabetes status, diagnosed with diabetes before the age of 30 years, and non-diabetic at intake without participation in follow-up surveys were excluded. study. The data analysis period was between January 2023 and September 2023.
Exposure in the study was physician diagnosis of diabetes. New CRC incidence was determined using the National Death Index linked to state cancer registries.
Cox proportional hazards regression models determined hazard ratios (HRs) adjusted for sex, education, recruitment source, CRC screening at recruitment, insurance coverage, alcohol intake and body mass index (BMI). The relationship between diabetes and CRC risk was also assessed among subgroups based on income, sex, ethnicity and race, smoking history, and obesity.
Study findings
Among 54,597 subjects, the median age at recruitment was 51 years, 64% of whom were female, 66% were African American, and 53% had an annual income of less than $15,000. Among participants, 68% had one or more follow-up visits and 39% attended the third follow-up visit. At enrollment, 20% and 28% documented new-onset and prevalent diabetes at follow-up, respectively.
People with diabetes were older compared to those with new-onset diabetes and those without self-documented diabetes, with a median age of 54, 50, and 50 years, respectively. People with diabetes were more likely to be female, African-American, less educated, obese, and have lower annual incomes compared to people without diabetes. Compared with non-diabetics, people with diabetes at study entry were more likely to be heavy drinkers, smokers, have health insurance, and undergo CRC screening.
Individuals with CRC were older, more likely to be African American, less educated, and had participated less in CRC screening compared with those without CRC. A total of 289 diabetic subjects out of 25,992 developed CRC compared with 197 out of 28,605 non-diabetic subjects.
A diagnosis of diabetes increased the risk of CRC by 47%, with an HR of 1.5. These associations were strongest among subjects who did not undergo screening colonoscopy and had a history of smoking with HRs of 2.1 and 1.6, respectively.
Associations were stronger among women than men, with HRs of 1.6 and 1.3, respectively, and among those newly diagnosed with diabetes. Compared with diabetes duration of five to ten years, people with diabetes for two to five years were at greater risk for CRC. CRC risk was lower among people with diabetes for 10 years or more.
Biological pathways, including hyperinsulinemia and hyperglycemia, may contribute to the association between T2D and increased risk of CRC. CRC cells prefer a glycolytic metabolism. Therefore, hyperglycemia may aid in carcinogenesis by providing the extra glucose needed for cell proliferation. Similarly, hyperinsulinemia may promote glucose uptake in cancer cells and interact with insulin receptors to stimulate proliferative pathways and increase risk for CRC.
conclusions
The study findings demonstrate that diabetes was associated with an increased risk for cardiovascular disease, thus indicating that glycemic control may reduce the risk for CRC. This relationship was weaker for people who had a colonoscopy, thus indicating that screening colonoscopy for people with diabetes may help moderate the risk.
