Does excessive sitting increase the risk of cancer?

Prolonged sitting—whether at a desk, watching television, or using a smartphone—is a common modern habit. While a sedentary lifestyle is a well-known risk factor for many chronic diseases, new evidence suggests it may also be linked to an increased risk of cancer.

The Link Between Prolonged Sitting and Cancer

Replacing extended periods of inactivity with even light physical activity can effectively reduce health risks. According to a study published in the journal PLOS Medicine, slow walking, daily chores, or small daily movements can yield significant positive impacts.

Researchers analyzed wearable device data from over 91,000 UK Biobank participants, monitoring them for an average of 12 years. The results showed that those who sat for extended periods faced a significantly higher risk of both developing and dying from cancer. Specifically, cancer mortality risk increased by about 10% for every additional hour of continuous sitting.

Cancers linked to a long-term sedentary lifestyle include colorectal, breast, liver, kidney, pancreatic, ovarian, esophageal, and thyroid cancers.

Conversely, swapping just one hour of sitting per day for light household chores—like ironing or washing dishes—was associated with a 12% lower risk of cancer death. Similarly, swapping 30 minutes of sitting for moderate activity, such as walking at a normal pace, reduced the risk by 8%.

The study further noted that just five minutes of daily high-intensity physical activity could reduce the risk of cancer death by up to 22%.

Why Inactivity Increases Risk

Dr. David Yasher, a hematologist and oncologist at MemorialCare Todd Cancer Institute in the United States, explained that an inactive lifestyle often leads to weight gain and obesity, which are known drivers for various types of cancer.

Excess body fat can trigger chronic inflammation, a process that helps cancer cells form and multiply. In addition, long-term inactivity can cause hormonal imbalances, elevating the risk of hormone-sensitive cancers such as breast cancer.

A Need for Further Research

However, researchers caution that this was an observational study. While it highlights a strong association, it cannot definitively prove that prolonged sitting is the direct cause of these cancer deaths.

Professor Kevin McConway, Emeritus Professor of Applied Statistics at the Open University (who was not involved in the study), noted that while the findings are significant, more extensive research is needed to confirm a direct causal link.