The Time You Spend Seated Each Day May Be Increasing Your Breast Cancer Risk

Prolonged periods of sitting have been the topic of health recommendations in recent years, with research linking it to many health issues, including high blood pressure, musculoskeletal disorder symptoms, and more exhaustion during the workday. It may also raise your risk of obesity, diabetes, and cardiovascular disease. A new study finds that how often you sit may impact your breast cancer risk, as well.

Research recently published in the journal Cancer Science investigated the impacts of excessive sitting on breast cancer risk among more than 36,000 women in Japan. Breast cancer is the most common cancer diagnosed in Japanese women, and prior research has linked increased physical activity with a lower breast cancer risk. The findings from this study back that up, showing that breast cancer rates were higher among women who sat for at least seven hours a day. This remained true even if women exercised in their free time, which suggests that intermittent bouts of exercise throughout the day may be a good idea.

Satomi Tomida, the study’s first author and endocrinology and breast surgery researcher at Kyoto Prefectural University of Medicine, says, “It’s best to sit less every day and frequently exercise, rather than doing all your exercise in your free time.”

The researchers gauged the impact of sitting by using health data from 36,023 participants in the Japan Multi-Institutional Collaborative Cohort Study. The participants were all women ranging in age from 35 to 69. Over a median follow-up period of about 9.5 years, 554 of them developed breast cancer.

After adjusting for other possible contributing factors related to breast cancer risk, the team found that women who sat for at least seven hours a day had a 36% higher risk of developing breast cancer. This was compared to women who sat less.

To see if leisure time exercise could help offset this, the researchers compared women who partook in regular exercise, like walking or jogging, with those who did not. They found that if women were working out at other times of the day but also sitting for at least seven hours, there was still an increased risk of breast cancer. The researchers say this indicates that the amount of time spent sitting has more of an impact than exercise.

Going forward, the team plans to continue researching the impacts of physical and sedentary activity on breast cancer risk. Until then, they encourage women – and men – to find ways to move during their otherwise sedentary workday. Some ways to do this include getting up to stretch, exercising during breaks, standing at work when possible, and walking away from your work computer at regular intervals. You can set a reminder if it helps.