Study Links Restless Legs Syndrome With ED

Study Links Restless Legs Syndrome With Erectile Dysfunction

January 1, 2010 — Men who experience symptoms of restless legs syndrome (RLS) 15 or more times per month have almost a 2-fold higher risk of also having erectile dysfunction (ED) than men without RLS, a new study has found.

The association was independent of age, body mass index, use of antidepressants, anxiety, and other possible risk factors for RLS.

"These results are not surprising — they are pretty consistent with our hypothesis — but more study is needed to explore the exact mechanism behind this association," said lead author Xiang Gao, MD, PhD, instructor of medicine at Harvard Medical School, associate epidemiologist at Brigham and Women's Hospital, and research scientist at the Harvard School of Public Health in Boston, Massachusetts.

The hypothesis that there is a link between RLS and ED was based in part on the fact that both conditions are associated with dopamine function and with sleep disorders, said Dr. Gao.

Their research appears in the January 1 issue of the journal Sleep.

Health Professional Follow-up Study

The study subjects were men who participated in the Health Professional Follow-up Study (HPFS). The HPFS included male US health professionals (dentists, optometrists, osteopaths, podiatrists, pharmacists, and veterinarians) aged 40-75 years who completed questionnaires every 2 years beginning in 1986.

This current analysis included 23,119 men who completed questions related to RLS and were free of diabetes and arthritis. Of these 23,119 men, 4.1% met criteria for RLS and had symptoms of restless legs 5 or more times per month.

Characterized by unpleasant leg sensations (eg, crawling or pain) and an almost irresistible urge to move the legs — symptoms that worsen at night — RLS negatively affects sleep, daily activities, and quality of life. The condition affects 5% to 15% of the adult population.

On the 2000 and 2004 questionnaires, HPFS participants rated their ability to maintain an erection as being very poor, poor, fair, good, or very good. Ratings of poor or very poor were considered to be ED.

Also through questionnaires, researchers collected information on potential confounders, including age, ethnicity, smoking habits, weight, height, physical activity, use of medicine, level of anxiety, and history of major chronic diseases.

The study found that men with RLS had a higher prevalence of ED than those without RLS in every age group. Up to 2004, 52.9% of RLS patients reported ED compared with 40.3% of those without RLS (age adjusted odds ratio [OR], 1.47).

Severity Raises Risk

The more frequent the RLS symptoms, the higher the risk of having ED. Compared with men with no RLS, the age-adjusted OR was 1.22 for men who had RLS 5 to 14 times per month and 1.93 for those with RLS 15 or more times per month. After adjusting for age, body mass index, smoking habits, use of antidepressants, and other covariates, the OR was 1.16 for men with lower-frequency RLS and 1.78 for those with higher-frequency RLS. These associations were not altered after excluding men with Parkinson's disease, which is also associated with dopamine deficiency.

"The frequency of symptoms is a marker of severity, so this means that men with more severe RS are more likely to have ED; that's a dose-response association," said Dr. Gao.

The researchers performed several sensitivity analyses and found similar results. The ORs comparing men with the greater RLS frequency with those with no RLS were 1.74 after excluding participants with the highest levels of anxiety, 1.81 after excluding participants with myocardial infarction or stroke, and 1.68 after excluding participants with hypertension. Excluding participants who used antidepressants and including those with diabetes or arthritis did not change the associations.

Possible Mechanisms

There are several possible mechanisms that might explain the association between RLS and ED, said Dr. Gao. Hypofunction of dopamine in the central nervous system is associated with both conditions and could at least partly explain the association. Current treatments for RLS include dopamine-based approaches, and experimental studies show that dopamine-related drugs may be effective for ED too, although more study is needed to confirm this, said Dr. Gao.

The association could also be a result of sleep apnea or other sleep disorders that may affect hormonal, neural, and endothelial physiology. There could also be a genetic contribution — people with a specific mutated gene that affects spinal cord development have a higher risk for RLS, added Dr. Gao.

The presence of other chronic conditions, such as cardiovascular disease, could play a role, although the study controlled for these variables.

Because this study was cross-sectional, it is not possible to determine whether RLS is causing ED or the other way around. The next step is to replicate these findings in a longitudinal study, said Dr. Gao. "The most important thing is to know whether RLS is a clinical marker for ED — to find out if people with RLS have a higher risk of developing ED in the future."

Another limitation of the study was that it used only 1 question to determine erectile function.

Dr. Gao emphasized that since this is the first, and therefore the only, study to look at the relationship between RLS and ED, more studies, especially prospective ones, are needed before any treatment implications will become clear. "If a prospective study shows RLS could be a marker for the developing of ED in future, then maybe treating RLS could be a benefit for ED, but at this time we can say nothing," said Dr. Gao.

It's unclear whether women with RLS have an increased prevalence of sexual dysfunction, he said.