PLOS Medicine: One extra hour of prolonged sitting is linked to a higher risk of cancer death

Scientists have found that each additional hour spent sitting without breaks is associated with a higher risk of dying from cancer, while interrupting periods of sitting with movement is associated with a lower risk. The study was published in PLOS Medicine.

The harmful effects of a sedentary lifestyle have long been known, but researchers wanted to determine what matters more — the total amount of time spent sitting or how continuously that time is accumulated. To investigate this, they used objective data from wearable motion sensors rather than questionnaires.

Researchers led by epidemiologist Frederick Ho of the University of Glasgow analyzed data from more than 91,000 participants in the UK Biobank, who were followed for approximately 12 years. The researchers separately assessed “prolonged” sitting, defined as episodes lasting more than 30 minutes without interruption.

The study found that each additional hour of prolonged sitting was associated with a 9% increase in cancer mortality. In contrast, each additional hour of sitting interrupted by movement was associated with an 18% lower risk of death from cancer. Replacing one hour of prolonged sitting with light physical activity was associated with an approximately 12% lower risk.

“Being sedentary for more than 30 minutes at a time is particularly associated with an increased risk of cancer. Interrupting sitting with something as simple as a short walk may be protective,” Frederick Ho said.

According to the authors, health may depend not only on reducing the total amount of time spent sitting, but also on regularly getting up and moving throughout the day.

This is a simple and accessible habit: getting up, walking around or stretching every half hour can help break up prolonged periods of sitting. Researchers associate the harmful effects of prolonged sitting with metabolic disturbances, increased inflammation and higher blood sugar levels — processes that may contribute to tumor development.

The findings may be particularly relevant to office workers, who spend much of the day sitting, often without even realizing how long they have remained inactive.

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