In a study published in Scientific Reports, researchers examined the correlation between differences in body mass and the risk of colorectal cancer.
This large, nationwide, population-based, cohort study investigated the correlation between obesity status at 4-year intervals and the risk of colorectal cancer.
The primary outcome of this study was new colorectal cancer cases, defined as having the ICD-10 code of C18-C20, diagnosed in either inpatient or outpatient settings. The incidence of colorectal cancer was calculated as a ratio of the number of events to person-time at risk. Participants were followed until the diagnosis of colorectal cancer, death, or the last day of the study period (December 2019).
The study involved 3,858,228 individuals who participated in the national screening programs in 2005 and 2009, of whom 47,894 (1.24%) participants were diagnosed with colorectal cancer. The average age of participants with colorectal cancer was greater than that of participants without colorectal cancer (59.0 ± 11.6 years vs. 49.0 ± 12.9 years, P <.001).
The percentages of men and women with colorectal cancer were 64.2% versus 35.8%, respectively. Additionally, between-group differences in economic status, smoking, alcohol intake, regular physical activity, BMI, waist circumference (WC), history of diabetes, hypertension, and dyslipidemia were significant (all, P <.001).
The initial average BMI was 24.1 ± 3.0 in patients with colorectal cancer and 23.7 ± 3.1 in controls (P <.001), and the final average BMI was greater among patients with colorectal cancer (24.1 ± 3.0 vs. 23.8 ± 3.1, P <.001). The percentages of patients who were underweight or normal weight (BMI <23 kg/m2), overweight (BMI 23.0-24.9 kg/m2), and obese (BMI ≥25.0 kg/m2) were 40.0%, 26.2%, and 33.8%, respectively. The average follow-up durations for colorectal cancer, colon cancer, and rectal cancer were 9.18 ± 1.1 years, 9.18 ± 1.1 years, and 9.21 ± 1.1 years, respectively.
The authors stated that although the risk of obesity was greater in men, both men and women in the obese/obese group demonstrated a heightened risk of colon cancer, and the variations in results may be attributed to race, weight comparison points, and comparison tools, such as body weight, BMI, and WC. They also noted that because estrogen is an important difference between men and women, pre- and postmenopausal women were compared by grouping women by age.
Based on their findings, the authors wrote, “The incidence of colorectal cancer was higher in the obese/obese group than in the non-obese/non-obese group. This trend was more apparent in men, especially for colon cancer. The obese/obese group in older age over 50 was significantly associated with colorectal cancer but not at a younger age.”
The authors concluded that persistent obesity—defined as BMI ≥25 kg/m2—was considerably correlated with colorectal cancer in both men and women. Therefore, to thwart the development of colorectal cancer in both men and women, prevention of persistent obesity and avoidance of weight gain are beneficial.
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