Rare sleep disorder that causes violent kicking and punching tied to smoking, pesticides

A rare sleep disorder in which people violently kick, punch or thrash in their sleep may be more common in smokers and people heavily exposed to pesticides, new research suggests.

The sleep-kicking disorder is actually called "REM sleep behavior disorder." According to WebMD, people typically lose muscle tone (paralysis) during the rapid eye movement (REM) stage of sleep - but that doesn't occur in people with the disorder, causing them movements (sometimes violent) that can seriously harm the individual or their sleep partner. It is estimated to affect only 0.5 percent of adults.

"Until now, we didn't know much about the risk factors for this disorder, except that it was more common in men and in older people," study author Dr. Ronald B. Postuma, a sleep researcher at the Research Institute of the McGill University Health Centre (MUHC) in Montreal, said in a press release. "Because it is a rare disorder, it was difficult to gather information about enough patients for a full study. For this study, we worked with 13 institutions in 10 countries to get a full picture of the disorder."

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