London: Sleeping for less than six hours a night boosts the risk of dying from a heart attack or stroke.
But beware -- those who have too much sleep are also more likely to suffer a heart attack, the European Heart journal warned.
While the extra slumber is unlikely to be the cause, long-term illnesses such as heart disease often make sufferers feel tired. So sleeping for longer than nine hours a night may be an early warning sign.
Francesco Cappuccio from the University of Warwick Medical School, who led the study, said: "The trend for late nights and early mornings is actually a ticking time bomb for our health, so you need to act now to reduce your risk..."
Researchers found that those who slept for less than six hours were almost 50 per cent more likely to suffer a heart attack and 15 per cent more at risk of strokes.
Not having enough sleep decreases the levels of leptin in our blood, which means we do not feel as satisfied after eating, a newspaper reported.
At the same time, it raises the levels of ghrelin, responsible for triggering our appetite, thus making us feel hungrier.
Poor sleepers tend to eat more and are more likely to be obese, so are at greater risk of high blood pressure and heart disease, which lead to heart attacks and strokes.
Experts recommend adults get at least six or seven hours` shut-eye a night to stay healthy.
Researchers looked at the sleeping habits of almost 475,000 participants from 15 previous studies across eight countries, including the UK, the US, Japan, Sweden and Germany.