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For harried workers – and parents, especially – a good night's sleep is the holy grail.

Bleary-eyed masses mull over mattress options, read up on " sleep hygiene" and even debate over the best side of the bed. (Hint: it's the left.)

But the quest for healthy slumber should focus on quantity, a study suggests.

People who get less than six hours of sleep a night are twice as likely to have a stroke or heart attack, ABC News reports.

The findings are alarming, considering that nearly a third of Canadian adults get less than six hours a night, the CBC has reported.

In addition to the risk of heart disease, too little sleep has been linked to diabetes, excess stress hormones, weight gain and workplace accidents.

On the other hand, too many Zzs may be unhealthy too. People who sleep more than eight hours a night have an increased chance of chest pain and coronary artery disease – a narrowing of the blood vessels that supply blood and oxygen to the heart, researchers discovered.

"Based on these findings, it seems getting six to eight hours of sleep everyday probably confers the least risk of cardiovascular disease over the long term," study author Dr. Rohit Arora, chair of cardiology at Chicago Medical School, told ABC News.

Researchers didn't look at the effects of bi-modal sleeping patterns, which involve sleeping in shifts that add up to seven or eight hours of shuteye.

But Dr. Arora's research is consistent with a review of studies on sleep dating from 1966 to 2009 and published in the European Heart Journal, which showed that sleeping too little or too much increases the chances of death from stroke and coronary artery disease.

There couldn't be a better argument for experimenting with black-out blinds, ear plugs and sleep-training the kids.

Do you get six to eight hours of sleep each night? How much do you need to feel bright eyed and bushy tailed?