Men who jerked and flexed their legs involuntarily at night were more likely to develop cardiovascular disease in a new study of sleep and chronic disease in the 65-and-older age group.
During a one-night sleep assessment, more than two-thirds of men had the involuntary movements, which usually occur in the foot or at the ankle or hip joint, and most of them woke up during the night because of it.
Over the next few years, those men had a higher risk for cardiovascular events, including heart attack, stroke and blocked or ruptured arteries.
So-called periodic limb movements are considered a different condition from restless leg syndrome (RLS). In contrast to restless legs, people with periodic limb movements often don't realise it, said Dr Brian Koo, the study's lead author from Case Western Reserve University School of Medicine in Cleveland, US. One clue, though, is sleepiness during the day as a result of many brief nighttime wake-ups. Sleep tests are needed to make the diagnosis, researchers said.
They estimate that between 5% and 8% of the US general population experience periodic limb movements and movements in the most severe cases may "number well into the hundreds each night".
For the current study, Dr Koo and his colleagues gave single-night tests to close to 3,000 men age 65 and older.
They found that 70% had those leg movements at least five times per hour while they slept and at least 60% woke up - without realising it - at least once an hour.
Over the next four to five years, 500 of the men had a first cardiovascular event, the researchers reported in Circulation.
The limb movements weren't linked to any one particular endpoint. But when all cardiovascular endpoints were combined, men with frequent leg movements had a 25% to 30% higher risk than men with no or few involuntary movements. Those who woke frequently during the night were 20% to 25% more likely to reach the combined endpoint than men who slept soundly.
The researchers think it's possible that the leg movements and arousals also come with increases in heart rate or blood pressure during sleep - which could, over time, increase heart-related risks.
The jerks and flexes are sometimes treated with medications for Parkinson's disease and anti-convulsants.
Dr Koo said more studies are needed before his team's findings should lead to any changes in diagnosis or treatment of involuntary nighttime activity.
Leg movements not benign
"I don't think it would change the implications of management at this point," agreed Dr Brian Murray, who studies sleep at Sunnybrook Health Sciences Centre in Toronto and wasn't involved in the new paper.
"We need a further study to see if you treat these movements, would you decrease the risk of cardiovascular diseases?" he told Reuters Health. Also, he said, it's unclear how severe or frequent the leg movements have to be to warrant concern. Still, he said that research "continues to paint a picture that indeed the limb movements aren't as benign as we thought they were".
"There's still a lot that needs to be sorted out, but potentially sleep in general is important to look at in terms of cardiovascular risk," Dr Koo told Reuters Health.
The study authors caution that the findings shouldn't be generalised to women, to men under 65 or to non-white men - since less than 10% of those in their study were minorities.
Dr Fouzia Siddiqui, a sleep specialist at Rockingham Memorial Hospital in Harrisonburg, Virginia, pointed out that the sleep tests were done in people's homes, instead of in the lab where they may have been more precise. She called the study "a beginning" toward exploring a possible link between nighttime movements and cardiovascular disease. - (Genevra Pittman/Reuters Health, September 2011)