Washington August 1:
            Six, seven or eight -- so how many hours of sleep are enough for you? It's probably best to aim for seven hours of quality shut-eye every night, says a new study led by an Indian-origin researcher.
Anoop Shankar and his team at West Virginia University has found that those who sleep more or less than seven hours a day are at a raised risk of developing coronary heart disease, the 'Sleep' journal reported. They have based their findings on an analysis of data gathered in a national US study in 2005 on 30,000 adults.
The study found that the subjects who said they slept nine hours or longer a day were one-and-a-half times more likely than seven-hour sleepers to develop heart disease. And, adults under 60 who slept five hours or fewer a night raised their risk of developing cardiovascular disease more than threefold compared to people who sleep seven hours, the study found.
According to the researchers, short sleep duration is associated with angina, while both sleeping too little and too much are linked to heart attack and stroke. The results remained the same after considering age, sex, race, whether the person smoked or drank, whether they were fat or slim, and whether they're active or couch potato.
However, the researchers were unable to find out the exact reason between how long one sleeps and heart disease. But they pointed out sleep duration affects endocrine and metabolic functions and sleep deprivation lead to impaired glucose tolerance, reduced insulin sensitivity and elevated blood pressure, all of which raise risk of hardening arteries.
Shankar said that doctors should screen for changes in sleep duration when assessing patients' risk for heart disease and that public health initiatives consider including a focus on improving sleep quality and quantity.