Prolonged Sitting Linked to Higher Cancer Risk, Even With Exercise

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NEW DELHI: You may faithfully hit the gym every morning, go for a brisk walk or complete your daily yoga session. But if your job keeps you glued to a chair for the next eight to 10 hours, that workout alone may not be enough. A study published in the peer-reviewed journal PLOS Medicine has found that prolonged sitting is associated with a higher risk of developing and dying from cancer, even among people who meet recommended physical activity levels. Findings are particularly relevant for millions of Indians with desk-bound jobs as well as students preparing for competitive exams. Tracking more than 91,000 adults for over 12 years, researchers found that people who spent more time each day sitting continuously for more than 30 minutes had a progressively higher risk of dying from cancer. Every additional hour of such prolonged sitting was associated with about a 10% higher risk compared with people who spent an hour less doing so. Swapping some sitting time for physical activity was associated with a lower risk, of 12% with an hour of light activity, 8% with 30 minutes of moderate activity and 22% with five minutes of vigorous activity. “Regular exercise remains essential, with adults advised to get 150-300 minutes of moderate physical activity a week, but it should be combined with frequent movement throughout the day. Spending long, uninterrupted hours seated appears to independently increase the risk of cancer and cancer-related mortality,” said Dr Abhishek Shankar, assistant professor, Department of Radiation Oncology, AIIMS Delhi. Explaining the possible biological mechanisms, he said prolonged sitting slows muscle activity, impairs glucose and fat metabolism, and promotes insulin resistance, chronic inflammation, weight gain and hormonal changes. “Sitting itself does not directly cause cancer, but these changes, along with reduced blood circulation and impaired immune function, may increase the risk of colorectal, breast and endometrial cancers over time, especially when combined with other unhealthy lifestyle factors,” he said. Researchers cautioned that the observational study does not establish a direct cause-and-effect relationship. However, because activity levels were measured using wearable devices rather than self-reported questionnaires, findings provide stronger evidence than many earlier studies linking sedentary behaviour to cancer outcomes. Dr Amit Upadhyay, senior consultant, haematology and oncology, PSRI Hospital, said the focus should be on breaking up long periods of sitting rather than simply reducing total sitting time. “For people with desk jobs, regular movement breaks are key. Stand up every 30-60 minutes, take a five-minute walk, use a standing desk where possible, walk during phone calls and avoid sitting while waiting for files to download or meetings to begin. People working from home should be especially mindful because they often miss the natural movement that comes with commuting or walking around an office. The health risks of prolonged sitting develop silently over time, making these small but regular movement breaks an important part of daily routine,” he said.