Spending more leisure time sitting down increases the risk of cancers of the breast, ovaries and bone marrow in women, scientists have found.

More time sitting down increased the chance of cancer by 10 per cent in women – but did not affect men.

For years, too little physical activity has been recognised as bad for one’s health.

But recently researchers have focused on sitting down as posing a specific threat.

Researchers for the American Cancer Society studied 146,000 people – 69,260 men and 77,462 women between 1992 and 2009.

During this time period 18,555 men and 12,236 women were diagnosed with cancer.

The researchers found leisure sitting was linked to with a 10 per cent higher risk of cancer – even after factors such as total physical activity, body mass and other factors were taken into account.

The authors conclude: ‘Longer leisure time spent sitting was associated with a higher risk of total cancer risk in women, and specifically with multiple myeloma [bone marrow cancer], breast cancer, and ovarian cancers.

'But sitting time was not associated with cancer risk in men.

‘Further research is warranted to better understand the differences in associations between men and women,' they added.

American Cancer Society guidelines recommend reducing sitting time when possible.

Previous research by the University of Regensburg, Germany, found sitting raised the risk of bowel and lung cancers.

Scientists there found each 2-hour per day increase in sedentary time was related to a statistically significant 8 per cent increase in colon cancer risk and 10 per cent increase in endometrial (womb) cancer risk.

However, this previous study – which reviewed 43 other studies - did not find a link between sitting and a higher risk of breast and ovarian cancer. 

The authors of the German study, Daniela Schmid and Dr Michael Leitzmann, said one possibility for the rise in cancers in their study was that sitting down is often associated with TV viewing, which is in turn often accompanied by eating junk food and drinking sugary drinks. 

Other possibilities include getting less Vitamin D, produced in our bodies when we are exposed to sunlight.

In February, Apple’s chief executive Tim Cook announced ‘sitting is the new cancer’ and that his smartwatch was set to remind him to get up and move at ten minutes every hour. 

Last year researcher Dr Emma Wilmot and her collagues at the University of Leicester analysed 18 studies incorporating a total of 800,000 people.

The team found that people who sit the longest are twice as likely to have diabetes or heart disease as those who sit the least. 

The team also reported that sitting for long periods appears to raise the risk of kidney disease, especially in women. 

And that muscle, joint and back pain, becoming increasingly common among middle-class high-achievers, who spend most of their lives sitting down.

Dr Wilmot said: ‘When we sit for long periods of time, enzyme changes occur in our muscles that can lead to increased blood sugar levels. 

'The effects happen very quickly, and regular exercise won’t fully protect you.’ 

Courtesy: Daily Mail