The numbers are in and they’re rather alarming. According to a four-year follow-up study with more than 200,000 men and women, as many as two in every three cigarette smokers will die from this habit. The work, published in BMC Medicine this week, also estimated that smokers will die 10 years earlier than non-smokers.

"We knew smoking was bad but we now have direct independent evidence that confirms the disturbing findings that have been emerging internationally,” Australian National University’s Emily Banks says in a news release. Researchers had previously assumed that only about half of smokers would die of a smoking-related illness, such as cancer and heart and respiratory diseases. However, newer studies in U.K. women, British doctors, and American Cancer Society volunteers have upped that figure to 67 percent. "We have been able to show exactly the same result in a very large population-wide sample," Banks adds.

The Sax Institute's 45 and Up Study sampled about a quarter million individuals from the general population of New South Wales—it's the largest longitudinal study of healthy aging in the Southern Hemisphere. Banks’ team analyzed the questionnaire answers and hospitalization data of 204,953 recruits who joined the study from 2006 to 2009. Of those participants, 7.7 percent were current smokers, 34.1 percent were past smokers, and 5,593 deaths had accrued by 2012.

“Even with the very low rates of smoking that we have,” Banks says, “we found that smokers have around three-fold the risk of premature death of those who have never smoked.” Australia has one of the lowest smoking rates in the world (13 percent of the population), and you may have seen images of their plain cigarette packaging: drab dark brown with a fairly graphic health warning.

Furthermore, the team also found that, compared with non-smokers, smoking 10 cigarettes a day doubles the risk of dying and a pack a day increases the risk four- to five-fold.

But here’s some good news! Among past smokers, the risk of premature death diminished with time. In people who quit before age 45, their mortality was almost the same as never-smokers.