Obesity, Weight Gain May Be Tied to Early-Onset Colorectal Cancer in Younger Women

Obesity and weight gain in early adulthood may be associated with an increased risk of early-onset colorectal cancer (CRC) in women under the age of 50, according to a new study published in JAMA Oncology.

In the United States, CRC incidence and mortality among younger adults have been steadily increasing for reasons unknown. The study investigators aimed to determine whether obesity and weight gain could be potential contributors to increased risk of early-onset CRC in this population.

Using the Nurses’ Health Study II, which began in 1989, researchers analyzed data from 85,256 women aged 25 to 44 years who were without cancer or inflammatory bowel disease at enrollment. Detailed information on body weight through the life course, family and endoscopy histories, and lifestyle factors were collected at study baseline and every 2 to 4 years. By 2011, 114 early-onset CRC cases under the age of 50 were diagnosed.

According to the study, women with the highest body mass index (BMI), defined as a BMI greater than 30, had almost twice the risk of early-onset CRC compared with women with the lowest BMIs, defined as 18.5-22.9. The elevated risk associated with increasing BMI was also found among women with no family history of the disease. Overall, the researchers concluded that higher current BMI, BMI at 18 years of age, and weight gain since early adulthood were associated with an increased risk of CRC under age 50.

“There are few known risk factors for early-onset colorectal cancer,” Edward Giovannucci, MD, ScD, of the Harvard T.H. Chan School of Public Health, said in a press release about the findings. “If the screening age gets pushed before age 50, BMI may be one of the factors to take into account. Yet the analysis and risk-benefit analysis for early age of screening remains to be done.”

Diagnosis of early-onset CRC is rare, since cases are often not diagnosed until the later stages of the disease due to a lack of routine screening, the researchers noted. According to their estimates, approximately 22% of early-onset CRC cases could have been prevented had all participants in the study had a normal BMI.

The researchers concluded that further research is needed to determine why CRC rates and deaths among the younger population are increasing and whether BMI should be considered in deciding the appropriate age for an individual to begin screening.

References

Liu PH, Wu K, Ng K, et al. Association of obesity with risk of early-onset colorectal cancer among women. JAMA Oncology. 2018. Doi: 10.1001/jamaoncol.2018.4280

Obesity linked to increased risk of early-onset colorectal cancer [news release]. Washington University School of Medicine’s website. https://medicine.wustl.edu/news/obesity-linked-to-increased-risk-of-early-onset-colorectal-cancer/. Accessed October 12, 2018.