Sleeping more than nine hours and sitting too much during the day -- along with a lazy lifestyle -- can send you to an early grave, warn researchers.

According to the findings from non-profit organisation Sax Institute's "45 and Up Study", a person who sleeps too much, sits too much and is not 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 seven hours a day and too little exercise is defined as less than 150 minutes a week.

"This is the first study to look at how those things (sleep and sitting) 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 added.

Dr Ding and her colleagues from University of Sydney analysed the health behaviours of more than 230,000 of the participants in the "45 and Up Study".

They looked at lifestyle behaviours like smoking, high alcohol intake, poor diet and being physically inactive and added excess sitting time and too little/too much sleep into the equation.

The team found another problematic triple threat: smoking, high alcohol intake and lack of sleep (less than seven hours a night) is also linked to a more than four-times greater risk of early death.

"The take-home message is that if we want to design public health programmes 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," explained study co-author professor Adrian Bauman.

The 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," the authors noted in a paper published in the journal PLOS Medicine.