Highlights
- New research suggests that factors such as family history of colorectal cancer, sedentary behaviour and unhealthy diet may be associated with early-onset colorectal cancer risk.
- There has been a significant increase in colorectal cancer incidence rates among young adults under age 50 over the past few decades.
- More research could help inform prevention strategies targeted at younger people.
A recent study by Ontario Health (Cancer Care Ontario) has found possible reasons for the increase in colorectal cancer in younger age groups. Colorectal cancer is a disease that primarily affects older adults (over age 50), but it has been on the rise over the past few decades among adults under age 50 in many countries, including Canada.[1][2] The cause of this early-onset colorectal cancer is understudied and not well understood.
New research suggests that a family history of colorectal cancer, as well as modifiable factors such as longer sedentary (sitting) time, greater consumption of sugary drinks and a Western-like dietary pattern may each be associated with an increased risk of early-onset colorectal cancer (shown in Table 1).
| Variables | Response | Multivariable-adjusted odds ratio* | 95% Lower confidence limit | 95% Upper confidence limit |
|---|---|---|---|---|
| Family history of colorectal cancera | No | 1 | ||
| Family history of colorectal cancer | Yes | 2.37 | 1.47 | 3.84 |
| Sedentary timeb | Less than 5 hours per day | 1 | ||
| Sedentary time | 5 to less than 10 hours per day | 1.23 | 0.75 | 2.03 |
| Sedentary time | 10 or more hours per day | 1.93 | 1.02 | 3.65 |
| Sugary drinks (drinks per week)c | Less than 1 | 1 | ||
| Sugary drinks (drinks per week) | 1 to 6 | 1.86 | 1.11 | 3.13 |
| Sugary drinks (drinks per week) | 7 or more | 2.99 | 1.57 | 5.68 |
| Western-like dietary pattern scored | Quartile 1 (0 to 9) | 1 | ||
| Western-like dietary pattern score | Quartile 2 (10 to 13) | 1.46 | 0.8 | 2.67 |
| Western-like dietary pattern score | Quartile 3 (14 to 17) | 1.62 | 0.87 | 3.04 |
| Western-like dietary pattern score | Quartile 4 (18 to 27) | 1.92 | 1.01 | 3.66 |
* Adjusted for age (continuous, years), sex, family history of colorectal cancer (no, yes, unknown), regular aspirin or NSAID use (never or ever), smoking (never or ever), physical activity (active, somewhat active, insufficiently active), BMI (continuous, kg per m2), alcohol consumption (less than once per month, 1 to 3 times per month, 1 to 6 times per week, daily), red or processed meat intake (continuous, servings per week), total fruit and vegetable intake (continuous, servings per day), high-fiber food intake (continuous, servings per day) and calcium supplement use (never or ever)
a Among any first or second degree blood relative
b Average number of hours per day spent sitting (two years ago) at work, at school, at home, in a car/bus/train, and during leisure time (e.g., watching TV, playing video games, using computer, reading, socializing) 2 years ago, calculated as
c Sugary drinks such as soft drinks (excluding diet soda), vitamin drinks, energy drinks, and specialty coffee with syrup (e.g., mocha)
d Composite dietary score derived based on six non-beneficial (red meat, processed meat, sugary drinks, sugary desserts, fast food, and processed snacks) and three beneficial (fruits, vegetables, and high-fiber foods) components. For each non-beneficial component, subjects in the first, second, third, and fourth quartile of intake were assigned a value of 0, 1, 2, and 3, respectively; for each beneficial component, quartiles were reverse coded (i.e., 3, 2, 1, and 0, respectively). The final score was calculated by summing up values across all nine components, with higher scores indicating a more Westernized dietary pattern. The multivariable-adjusted OR was adjusted for all variables listed in footnote *, except for red/processed meat, total fruit and vegetable, and high-fiber food intake
A population-based case-control study was conducted in Ontario to investigate risk factors for early-onset colorectal cancer during 2018 and 2019. Eligible people with colorectal cancer ages 20 to 49 at their time of diagnosis were identified from the Ontario Cancer Registry and were asked to do an online epidemiology questionnaire after providing opt-in consent (by mailing back signed consent). The questionnaire asked about sociodemographic factors, family history, medical history, height, weight (body mass index), lifestyle (e.g., smoking, alcohol consumption, physical activity, sedentary time), and consumption of foods and beverages before diagnosis. A comparison group of healthy controls were recruited using random digit dialing methods and they were asked to do the same online questionnaire.
Findings from this study (Risk factors for early-onset colorectal cancer), which was funded by a Canadian Cancer Society research grant, were recently published in the journal Cancer Causes and Control.[3] However, the findings should be interpreted with caution given the small study sample size and the possibility of chance findings due to the multiple comparisons made. These findings need to be replicated in future studies before they can be used to inform prevention strategies aimed at younger adults.
Understanding risk factors for colorectal cancer among young adults is one of the first steps towards designing prevention strategies. Given the alarming increase in colorectal cancer among younger adults, more research into causes and prevention is warranted.
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