In a 2010 study published in the journal Sleep, researchers at the West Virginia University School of Medicine reviewed data from 30,397 people who had participated in the 2005 National Health Interview Study. They discovered that those sleeping fewer than 7 hours a night were at increased risk of heart disease. In particular, women under 60 who sleep 5 hours or fewer a night have twice the risk for developing heart disease.
According to a study in the journal Diabetes in 2011, University of Chicago and Northwestern University researchers found that when people with type 2 diabetes slept poorly at night, they had a 9 percent higher fasting glucose level, a 30 percent higher fasting insulin level, and a 43 percent higher insulin resistance level. Diabetics with insomnia fared even worse—their fasting glucose levels were 23 percent higher, their fasting insulin levels were 48 percent higher, and their insulin resistance levels were 82 percent higher than diabetics who didn't have insomnia.
Researchers at Tohoku University Graduate School of Medicine in Sendai, Japan, studied data from nearly 24,000 women ages 40 to 79, and learned that those who slept fewer than 6 hours a night had a 62 percent higher risk for breast cancer, while those who slept more than 9 hours a night had a 28 percent lower risk.
In findings presented at the May 2011 meeting of the American Urological Association, researchers at the New England Research Institute in Watertown, Massachusetts, reviewed data from 4,145 middle-aged men and women and here's what they discovered:
Five years of sleeping restlessly or too little (fewer than 5 hours a night) can increase by 80 to 90 percent a woman's risk of needing to wake at night to urinate (nocturia) or of becoming incontinent. A whopping 42 percent of the women classified themselves as restless sleepers, compared with 34 percent of the men. The researchers theorize that sleeping poorly causes inflammation, which in turn can lead to urinary problems.
In a study of 1,240 people published in 2011, Case Western University researchers found that those who slept fewer than 6 hours a night were 47 percent more likely to have colorectal polyps, which can become cancerous, than people who clocked at least 7 hours of sleep.
A 10-year study of some 16,000 people by researchers at the University of Copenhagen connected the dots between a lack of sleep and an increased risk of mortality. It turns out that the men who reported sleeping badly, especially those under 45, had twice the risk for death than men who reported sleeping well. And men who had three or more sleep disturbances a night had a suicide risk five times higher than men whose sleep was undisturbed. Though sleep disturbances didn't affect women's mortality, both women and men who reported sleep disturbances were more likely to have high blood pressure and diabetes.
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