September 4, 2026, 2:47 pm | Read time: 6 minutes
Whether in the office, in the car, or on the couch in the evening, many people spend several hours sitting each day. It’s long been known that prolonged sitting can harm health. A large study involving more than 90,000 people now provides new insights into the link with cancer. It suggests that not only the total time spent sitting matters, but also long periods of sitting without significant movement could play a role.
Researchers Study How Long People Sit at a Stretch
For the study published in 2026 in the journal PLOS Medicine, scientists analyzed data from 91,292 participants in the UK Biobank.1 Unlike studies that primarily look at total daily sitting time, the researchers wanted to know how these hours are distributed throughout the day.2
They distinguished between longer sitting periods and frequently interrupted sitting. A longer sitting period was defined as a time span of at least 30 minutes during which participants sat for at least 90 percent of the time. The scientists then examined whether these different sitting habits were linked to later cancer diagnoses and cancer-related deaths. They looked at cancer overall as well as types of cancer associated with obesity or type 2 diabetes. Additionally, 23 individual cancer types were studied.
More Than 91,000 People Participated in the Study
The participants were on average 56 years old, and 56 percent of them were women. Half were observed for more than 12.38 years, and the other half for less.
To capture movement as accurately as possible, participants wore a motion sensor on their wrist 24/7 for seven days. The data was analyzed using a machine learning-based method, allowing scientists to distinguish between sitting and light, moderate, and intense physical activity. The researchers also considered factors that could influence cancer risk, such as age, smoking, alcohol consumption, diet, education, and social factors.
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Long Sitting Periods Linked to Higher Cancer Mortality
During the observation period, 12,392 new cancer cases were registered. 1,726 participants died from cancer. A clear link with long sitting periods emerged: With each additional hour per day spent in such longer sitting periods, the likelihood of dying from cancer was statistically nine percent higher.
Interrupted Sitting Linked to Lower Risk
Overall, people with longer sitting periods were more likely to develop cancer. This was also true for cancer types associated with severe obesity or type 2 diabetes. Those who interrupted their sitting times more frequently with movement were less likely to develop cancer and also less likely to die from it.
However, the results do not mean that an additional hour of sitting automatically increases a person’s individual risk by nine percent. The numbers describe statistical correlations within the studied group.
What Happens When Sitting Time Is Replaced by Movement?
The researchers also calculated how the results would statistically change if part of the long sitting time were instead spent moving.
In these calculations, replacing an hour of longer sitting with an hour of light movement reduced the likelihood of dying from cancer by about twelve percent. Replacing 30 minutes of longer sitting with moderate movement reduced it by about eight percent.
Even five minutes of intense physical activity instead of longer sitting was associated with a lower likelihood of developing cancer. However, for cancer mortality, this result was not statistically clear.
Interestingly, additional movement does not necessarily mean sports. The study included everyday movements and slow walking as light physical activity.
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Does the Study Prove That Movement Breaks Protect Against Cancer?
No. The results show statistical correlations but do not prove that prolonged sitting causes cancer or that regular movement breaks protect against it.
The scientists observed the existing behavior of the participants and did not prescribe specific sitting or movement times. People with long and shorter sitting periods might also differ in other ways that affect their cancer risk. Although the researchers considered numerous possible influencing factors such as age, smoking, alcohol consumption, and diet, other influences cannot be completely ruled out in such an observational study.
Movement Was Measured for Only Seven Days
Another limitation concerns the duration of the measurement. Participants wore the motion sensors for only seven days. This one week may not reflect how much a person sits or moves over many years.
Additionally, while the sensors could detect whether someone was sitting or moving, they could not determine the context of the sitting time. For example, whether participants were working at a desk, driving, or sitting in front of the TV could not be determined.
Participants Do Not Fully Represent the Population
The studied group also has a peculiarity: The UK Biobank participants do not fully represent the British population. People who voluntarily participate in such large health studies are often healthier than the general population.
The researchers therefore verified their results with additional calculations. Among other things, they additionally considered BMI and existing conditions. They also conducted a calculation excluding cancer cases from the first two years of follow-up. The main correlations remained.
One Author Declares a Conflict of Interest
One of the study authors, Frederick K. Ho, works as a paid statistical consultant for PLOS Medicine–the journal in which the study was published. Therefore, he declared this activity as a potential conflict of interest. The other authors reported no conflicts of interest. The study was funded by the American Cancer Society and the US National Institutes of Health. According to the authors, the funders were not involved in the study’s planning, analysis, publication decision, or article writing.
Earlier Study Already Showed Increased Risk
A study published in 2020 in “JAMA Oncology” with around 8,000 participants had already found a link between prolonged sitting and cancer mortality. Among those who sat the most, the risk of dying from cancer was 82 percent higher than among those who moved more.3
Study leader Prof. Susan Gilchrist stated at the time: “This is the first study to definitively show a close link between too little movement and the risk of dying from cancer.”
Even short movement breaks could play a role. “Our study shows that even light activity positively impacts cancer survival chances,” Gilchrist said. She recommended interrupting sitting for about five minutes per hour.