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Too much sitting can raise cancer risk in women

SINGAPORE — You might want to consider standing up now, if you are reading this article in your chair.

A recent study found that women who sit more than six hours a day are at a higher risk of developing cancer — specifically breast, ovarian and blood cancers — compared with women who sit less than three hours daily. Photo: Thinkstock

A recent study found that women who sit more than six hours a day are at a higher risk of developing cancer — specifically breast, ovarian and blood cancers — compared with women who sit less than three hours daily. Photo: Thinkstock

SINGAPORE — You might want to consider standing up now, if you are reading this article in your chair.

Sitting for most of the day has been known to be bad news for health, raising one’s risk of developing lifestyle diseases, such as type 2 diabetes, cardiovascular disease and musculoskeletal problems.

New research has found that sitting may be especially deadly for women by putting them at a higher risk of certain cancers, including breast and ovarian cancers. In a recent large study published in the journal Cancer Epidemiology, Biomarkers and Prevention in June, researchers found that women who sit more than six hours a day are at a higher risk of developing cancer — specifically breast, ovarian and blood cancers — compared with women who sit less than three hours daily.

The former group who spent longer leisure time sitting also had a 10 per cent higher risk of developing any cancer, according to the findings.

The study was based on about 70,000 men and 77,000 women who took part in a long-running study American Cancer Society Cancer Prevention Study II Nutrition Survey cohort.

Cancer is the top killer in Singapore, causing almost 30 per cent of deaths last year, according to figures by Ministry of Health. Breast cancer takes the top spot for women’s cancers in Singapore, while ovarian cancer is the fifth-most-common cancer in women.

While more studies need to be done to confirm the link, local doctors said the most obvious connection between sitting and cancer would be inactivity, which can lead to obesity.

“Sitting often implies a more sedentary lifestyle. Modern living involves a lot of sitting down in the office. This, together with automation in all industries and transport, have made the modern-day woman much more sedentary,” said Dr Chia Yin Nin, obstetrician and gynaecologist at Gleneagles Hospital, Singapore.

About one-third of Singapore workers clock nine to 11 hours a day at the office, according to global survey findings from international business company Regus in 2011.

Obesity is a known risk factor for certain cancers, including women’s cancers such as breast, ovarian and uterine cancers, said Dr Chia.

She explained: “These cancers are linked to excess oestrogen (female hormone) in women’s body.

“Oestrogen is produced mainly in the ovaries, but it is also produced by fat cells which explains why obese women are at a higher risk of getting these cancers.”

THE HORMONE LINK

However, having a healthy weight does not mean you’re cleared of the cancer risk if you spend most of your time on the couch.

Dr Wong Seng Weng, medical director and consultant medical oncologist of The Cancer Centre, a Singapore Medical Group clinic, pointed out that the study still found an excess cancer risk in women who sit too much, even after correcting differences in body weight.

The negative effect of sitting also seemed more pronounced in women than in men.

Hormones may be one possible explanation for the phenomenon.

“Inactivity leads to a higher body fat to lean body mass ratio. In women, this may be the reason a sedentary lifestyle has a bigger impact on cancer risk, compared with men, although other factors may be involved. The fat tissue in women contributes to oestrogen formation, contributing to a higher risk of women cancers,” said Dr Wong.

He added that the lack of activity also leads to higher blood sugar and higher secretion of insulin.

“Apart from its commonly known function of controlling blood sugar, insulin also functions as a growth factor, and may potentially contribute to stimulation of cancer cell growth,”he said.

As such, periodic workouts may not be enough to negate the negative effects of long periods of inactivity in “active couch potatoes”, people who may be disciplined enough to exercise on a regular basis but spend a lot of their leisure time sitting, said Dr Wong.

GET OFF YOUR CHAIR

What can a deskbound office worker do to negate the deadly effects of sitting? Dr Wong advises making small adjustments to everyday habits.

“For instance, you may want to read this article standing,” he said.

Further research on the recommended frequency of breaking up “sitting time” is needed.

For a start, however, getting up and moving every hour would be a good habit to have, advised Dr Priathashini Krishnasamy, consultant in sport and exercise medicine at Tan Tock Seng Hospital.

The current physical activity guidelines are to accumulate 150 minutes of moderate intensity or 75 minutes of vigorous intensity activities spread out through the week, said Dr Krishnasamy.

This can be adapted according to the individual’s lifestyle, with each session of physical activity lasting 10 minutes or more.

Dr Krishnasamy added that those who wish to exercise at a higher intensity may need medical clearance before doing so.

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