Photo/Illutration A woman exercises while sitting (Asahi Shimbun file photo)

Sitting for more than seven hours a day increases the possibility of developing breast cancer in women by nearly 40 percent, a new study showed.

A research team from Kyoto Prefectural University of Medicine and other organizations concluded that a lack of muscle movement when sitting may cause poor blood circulation.

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

Recent studies found that prolonged sitting has adverse effects on health, increasing the risk of heart attacks, cerebrovascular diseases and diabetes. The World Health Organization also recommends reducing sedentary behavior.

Japanese spend more time sitting than many other countries, with data showing a median of seven hours per day.

The draft guidelines for physical activity and exercise, compiled by the health ministry’s panel of experts, also advise against extended periods of sitting.

STAND MORE

Focusing on breast cancer, the most common cancer among Japanese women, the research team surveyed about 36,000 women aged 35 to 69 regarding their health, time spent sitting and other lifestyle habits.

During a follow-up period with a median duration of 9.4 years, 554 of these women developed breast cancer.

For their analysis, the research team used a method that removes the influence of other breast cancer risks, such as age, body mass index (BMI), smoking, drinking, family history of breast cancer, childbirth experience and the presence or absence of hormone therapy.

The results showed that women who sat for over seven hours a day had a 36 percent higher risk of developing breast cancer than women who sat less.

The study also examined whether exercise during their spare time could reduce the risk of breast cancer for those who sat for more than seven hours a day.

The research team compared individuals who walk more than an hour a day, engage in exercise equivalent to jogging for over an hour a week, or exercise three times or more a week, with those who engage in less physical activity.

The results showed the risk of developing breast cancer was still higher in those who sit more than seven hours a day compared to those who don’t, regardless of how much exercise the person did.

“The amount of time spent sitting may be a bigger factor in the development of breast cancer than exercise,” Tomida said.

She recommends standing and stretching after sitting for a long time, using the stairs whenever possible and finding time to exercise during breaks in routines.

“Regardless of gender, Japanese who spend long periods sitting have an increased risk of death associated with lifestyle-related diseases, such as the accumulation of visceral fat, high blood pressure and diabetes,” said Teruhide Koyama, a lecturer in epidemiology at Kyoto Prefectural University of Medicine.

“It’s also important for men to sit less and to improve blood flow by exercising their muscles even while seated,” he said.

The study results were published in the electronic version of the medical journal, Cancer Science: https://doi.org/10.1111/cas.16020.

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