They're like the Riders of the Apocalypse - the four bad habits that, when combined, seriously damage the amount of time you'll live. Not surprisingly, they are: smoking, lack of physical activity, poor diet and drinking alcohol. But while each of them is bad for your health, researchers have discovered that the combination of them is almost certainly lethal. Researchers from the University of Oslo weighted, or gave points, to each of the bad behaviours, which they defined as any smoking, eating fruits and vegetables less than three times a day; indulging in less than two hours of physical activity a week; and drinking more than 14 units of alcohol if you're a woman, and more than 21 units if you're a man, every week. They then profiled the lifestyles of 4,886 people for 20 years, during which time 1,080 participants died, and they found that the risk of dying increased with each of the bad habits. People with all four bad habits, compared with people who had none of them, were three times more likely to die from heart disease, and four times more likely to die from other causes. Overall, the four habits combined took around 12 years off people's life expectancy. (Source: Archives of Internal Medicine, 2010; 170: 711-18).