Restless Legs Linked to CHD: New Prospective Data

September 14, 2012

September 14, 2012 (Boston, Massachusetts) — Restless-legs syndrome of at least three years' duration is associated with an increased risk of developing coronary heart disease, according to new prospective data from the Nurses' Health Study.

The study, led by Dr Yanping Li (Brigham and Women's Hospital, Boston, MA), was published online in Circulation on September 11, 2012.

Li commented to heartwire : "Several cross-sectional studies have found an association between restless-legs syndrome and heart disease, but until now this hasn’t been confirmed in prospective studies. Now we have shown this association to be true also in a prospective study, but it does appear to be dependent on the duration of symptoms."

Li and colleagues wondered whether a short period of restless legs would not be enough to show any association, whereas long-term symptoms might be more strongly linked to heart disease. And this is exactly what they found.

Mechanism Unclear

Li said the mechanism behind the association is not clear, but it is known that patients with restless legs have higher blood pressure and faster heart rates because of an increased sympathetic drive. This could lead to an increased risk of heart disease. Or another possibility is that the disrupted sleep is the mechanism. "We know that short sleep duration is linked to an increased risk of many chronic conditions, including heart disease, and patients with restless-leg syndrome are known to have severely disrupted sleep."

However, in the current study, the association between restless-legs syndrome of at least three years' duration and CHD remained significant after adjustment for sleep duration and snoring frequency, suggesting that sleep duration is not the only mechanism.

Li noted that restless-leg syndrome is hugely underdiagnosed, with estimates that only about 10% of cases have been diagnosed. "Most people don't think of it as a disease and don't go to see a doctor about it, and then many doctors don't take it seriously, either."

She hopes that these new data will lead to the condition being taken more seriously. "Doctors need to know that patents with these symptoms are at higher risk of heart disease and so need to be given more attention. While the best treatment for restless legs is not clear, at least these people should be identified as being a high-risk group for heart disease and be offered appropriate screening," she said.

In the Nurses' Health Study, a total of 70 694 women (mean age 67) who were free of coronary heart disease and stroke at baseline in 2002 were followed until 2008. Diagnosis of restless-legs syndrome was collected via questionnaire. Results showed that 1484 women reported having ever been diagnosed with restless legs at baseline. During a mean of 5.6 years of follow-up, there were 698 cases of MI or CHD death in the whole population. After adjustment for other risk factors, these women had a marginally higher risk of having a nonfatal MI or coronary death than the rest of the population. This risk depended on duration of symptoms, with no association seen for those with less than three years of symptoms and a 70% increased risk for those who had had symptoms for more than three years.

Hazard Ratio for MI or CHD Death in Women With Restless Legs

Group HR (95% CI)
Any restless legs 1.46 (0.97–2.18)
Symptoms <3 y 0.98 (0.44–2.19)
Symptoms >3 y 1.72 (1.09–2.73)

The authors conclude that the long-term impact of restless-legs syndrome may contribute to cardiovascular disease, possibly through the increased sympathetic activation seen in the condition. But they add that "future study is needed to verify these associations and their respective hypotheses."

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