News · Longevity & Aging
At-home stool test screening tied to 43% fewer bowel cancer deaths in 376,511 Swedes
Many countries mail a simple stool test to people in their sixties. Sweden's staggered rollout let researchers compare invited and not-yet-invited birth years, and those who took part had far fewer deaths.
- An observational study of 376,511 people aged 60 to 69 in the Stockholm-Gotland region of Sweden, 2008 to 2021.
- Birth years were randomly assigned to be invited to stool-test screening earlier or later, or not at all.
- Being invited was linked to 26% fewer bowel cancer deaths, after accounting for later invitations and diagnoses.
- Actually doing the test was linked to 43% fewer deaths.
- The analysis relies on statistical adjustments, and the results could not be split between the two stool test types.
Many countries post a small kit to people in their fifties and sixties: collect a stool sample at home, send it off, and get called for a colonoscopy if it shows hidden blood. It is cheap and easy. Whether it saves lives on the scale of a whole region has been harder to show, because almost everyone eventually gets invited.
A study in JAMA Network Open, a journal of the American Medical Association (JAMA), used Sweden’s staggered rollout in the Stockholm-Gotland region to compare birth years invited earlier with those invited later. After accounting for who was actually tested, taking part was linked to 43% fewer deaths from bowel cancer.
What bowel cancer screening looks for
MedlinePlus explains that colorectal cancer is cancer that develops in the tissues of the colon or rectum, the last parts of the large intestine. Many start as small growths called polyps, which can bleed slightly long before they cause symptoms.
That hidden blood is what a stool test detects. As the authors note, population-based colorectal cancer (CRC) screening with fecal occult blood tests (FOBT) is widely implemented, but measuring its effect on deaths is difficult because there is rarely a clean unscreened comparison group.
How the Swedish screening study worked
Between 2008 and 2012, the region invited people aged 60 to 69 to screening by birth year. Some birth years were randomly assigned to be invited early, while the others formed a comparison group that was invited later, from 2013 to 2015, or not at all. The study included 376 511 individuals.
The researchers then tracked deaths from bowel cancer through 2021. They adjusted for two sources of blur: cancers in the invited group diagnosed long after screening stopped, and screening that the comparison group eventually received. Finally, they estimated the effect for people who actually returned their kits.
What happened to bowel cancer deaths
Invitation alone was linked to fewer deaths. After those adjustments the rate of bowel cancer deaths in the invited group was 26% lower, compared with a previous, unadjusted estimate of 14%.
Taking part mattered more. Once the analysis accounted for people who never returned a kit, participation was associated with a 43% reduction in bowel cancer deaths among people who did the test.
Why stool test screening matters
A stool test is one of the least demanding cancer screens available: no appointment, no bowel preparation, no sedation. That makes it a practical way to reach large populations, and this study suggests the payoff in lives can be substantial.
The gap between the two figures is the practical lesson. The benefit shows up only among people who actually return the kit, and in this program about one in eight people with a positive result did not go on to the recommended colonoscopy, which the authors note would further dilute the effect.
What a birth-year screening comparison cannot prove
Randomizing by birth year is not the same as randomizing individuals, and the 43% figure depends on statistical adjustments for people who did not take part and people who were tested outside the program. Those methods are reasonable but add uncertainty.
The authors could not separate the older chemical test from the newer, more sensitive FIT, because many people were invited to both, and the program used relatively high cutoffs for a positive result. Mortality from bowel cancer also fell over time for other reasons; the authors estimate this explains less than 2% of the effect.
What this changes about doing a stool test
If a screening kit arrives, doing it is one of the simplest ways to lower the risk of dying from bowel cancer. If the result is positive, the colonoscopy that follows is the step that turns a test into prevention.
The best screening test is the one that gets done. People who prefer a colonoscopy, or who have a family history or symptoms such as bleeding or a change in bowel habit, should talk to a doctor rather than rely on a mailed kit.
People also ask
What did the study find?
During follow-up there were 856 colorectal cancer deaths in the invited group and 812 in the control group. After adjusting for deaths diagnosed more than 2 years after the last invitation and for invitations in the control group, the mortality rate ratio for invitation was 0.74 (95% CI 0.58 to 0.94), a 26% reduction. After further adjusting for nonadherence, the ratio for participation was 0.57 (0.40 to 0.80), a 43% reduction.
What is a stool test for bowel cancer?
A kit used at home to collect a small stool sample, which a lab checks for traces of blood that cannot be seen. A positive result leads to a colonoscopy to look for cancer or growths called polyps.
What is the difference between the two test types?
The older guaiac test detects blood chemically, while the newer fecal immunochemical test, or FIT, uses antibodies and is more sensitive. Many people in this study were invited to both, so the results could not be separated.
Why are there two numbers, 26% and 43%?
The 26% reflects everyone who was invited, including people who never returned a kit. The 43% estimates the effect among people who actually took part.
Is a stool test as good as a colonoscopy?
They work differently. A stool test is easier and repeated regularly; a colonoscopy looks directly at the bowel. Both reduce bowel cancer deaths, and the best test is the one a person will actually do.
Should I do the test if one arrives in the mail?
Screening programs recommend it for the eligible age group, and a positive result should always be followed by the colonoscopy offered. This is general information rather than medical advice.