New cases of CRC and death are increasing among people younger than 50, and the reasons for this are largely unknown. This study used data from a large group of women in the Nurses' Health Study II to examine the association of obesity with CRC diagnosed before age 50.
The study included 85,256 women ages 25 to 42 who were free of cancer and inflammatory bowel disease when they enrolled in the study and followed up from 1989 through 2011.
Current body mass index (BMI), BMI at age 18 and weight gain since age 18 (exposures); relative risk, which is a statistical measure of probability, for new early-onset CRC (outcome).
This was an observational study. Researchers were not intervening for purposes of the study and cannot totally control for all the natural differences that could explain the study results.
The authors of the study are Yin Cao, M.P.H., Sc.D., of the Washington University School of Medicine, St. Louis, Missouri, and coauthors
There were 114 cases of early-onset CRC among the 85,256 women studied. Higher current BMI, BMI at age 18 and weight gain since early adulthood were associated with increased risk of early-onset CRC.
Obesity, which is a BMI of 30 or above, was associated with the highest risk.
The limitations of the study included mainly white women, so the findings need to be validated among other races/ethnicities and among men.
Obesity and weight gain since early adulthood were associated with increased risk of early-onset CRC. This study highlights the importance of weight control throughout life and the potential role of body weight in complementing CRC screening for the early detection of early-onset CRC.