Long nights and lazy days could send you to an early grave

• Being physically inactive + too much sleep

• Being physically inactive + too much sitting

• Smoking + high alcohol intake

Sleeping more than nine hours a night, and sitting too much during the day could be a hazardous combination, particularly when added to a lack of exercise, according to new findings to emerge from the Sax Institute's 45 and Up Study. 

The findings, published today in the journal PLOS Medicine, show that a person who sleeps too much, sits too much and isn't physically active enough is more than four times as likely to die early as a person without those unhealthy lifestyle habits. (Too much sitting equates to more than 7 hours a day and too little exercise is defined as less than 150 minutes a week.)

"Evidence has increased in recent years to show that too much sitting is bad for you and there is growing understanding about the impact of sleep on our health but this is the first study to look at how those things might act together," said lead author Dr Melody Ding.

"When you add a lack of exercise into the mix, you get a type of 'triple whammy' effect. Our study shows that we should really be taking these behaviours together as seriously as we do other risk factors such as levels of drinking and unhealthy eating patterns. "

Dr Ding and her colleagues from the University of Sydney analysed the health behaviours of more than 230,000 of the participants in the 45 and Up Study - Australia's largest study - which is looking at the health of our population as we age.

They looked at lifestyle behaviours that are already known to increase the risk of death and disease - smoking, high alcohol intake, poor diet and being physically inactive - and added excess sitting time and too little/too much sleep into the equation. They then looked at different combinations of all of these risk factors to see which groupings had the most impact on a person's risk of dying prematurely from any cause. 

As well as new evidence on the risky combination of prolonged sleep, sitting and lack of exercise, the researchers also found another problematic triple threat: smoking, high alcohol intake and lack of sleep (less than 7 hours a night) is also linked to a more than four-times greater risk of early death.

And several other combinations led to more than double the risk of early death: 

"The take-home message from this research - for doctors, health planners and researchers - is that if we want to design public health programs that will reduce the massive burden and cost of lifestyle-related disease we should focus on how these risk factors work together rather than in isolation," said study co-author Professor Adrian Bauman.

"These non-communicable diseases (such as heart disease, diabetes and cancer) now kill more than 38 million people around the world - and cause more deaths than infectious disease. Better understanding what combination of risk behaviours poses the biggest threat will guide us on where to best target scarce resources to address this major - and growing - international problem."