Apnea-Related Leg Movements May Signal Cardiovascular Disease

It is unknown if respiratory-related leg movements are just a marker of more severe obstructive respiratory events or whether the leg movements per se confer risk of cardiovascular disease.

Respiratory events that trigger leg movements predicted cardiovascular disease in older men with obstructive sleep apnea, researchers reported here.

After adjusting for clinic site, age, body mass index, and race, respiratory-related leg movements were associated with a 58 percent increased risk of incident cardiovascular disease in older men, according to Sayaka Aritake, PhD, of Tokyo Medical University in Japan, and colleagues.

In a separate model that took into account antidepressant use, hypertension, self-reported diabetes, cardiovascular disease history, smoking, demographic factors, and apnea hypopnea index, respiratory-related leg movement was associated with a 71 percent increased risk of incident cardiovascular disease, Aritake said during an oral presentation at the SLEEP meeting.

Aritake noted that “obstructive sleep apnea is a risk for incident hypertension and cardiovascular disease” and that “obstructive respiratory events that terminate with a leg movement produce larger heart rate increases than those without a leg movement.”

The authors analyzed independent associations between respiratory-related leg movements and increased risk of incident cardiovascular events in a prospective observational study of 633 older men with leg movement data and obstructive sleep apnea in the MrOS community-based cohort sleep study. Participants had an apnea hypopnea index score of 10 or greater.

Respiratory-related leg movement was defined as leg movement lasting 0.5 to 5 seconds with an onset of up to 2 seconds before or after the termination of a respiratory event.

The men in the study had a mean age of 81.2 and self-recorded data through an in-home, overnight, single night, unattended polysomnography. Leg movement was measured through piezoelectric sensors. Data was also collected on EEG, EOG, Chin EMG, ECG, airflow, inductance plethysmography, pulse oximetry, and body position.

Participants were asked to report treatment for potential cardiovascular disease conditions in the 4 months prior to the study, and researchers gathered clinical data. Some 7.3% reported a cardiovascular event.

Data were adjusted in three models. Model one included clinical site, age, BMI, and race. Model two included all of those and antidepressant use, hypertension, self-reported history of diabetes, self-reported history of cardiovascular disease, smoking, and apnea hypopnea index. Model three included all variables in model two with periodic limb movement index score. The authors later excluded data from model three because of its effects on outcome significance.

Data showed that with each standard deviation increase in the ratio of respiratory-related leg movements, the risk of new cardiovascular disease events increased by 29 percent in adjusted models.

“It is unclear if respiratory-related leg movement is just a marker of more severe respiratory events or whether the leg movements per se confer risk, as has been previously demonstrated with periodic leg movements of sleep in this same cohort,” Aritake concluded.

Aritake also noted that some limitations of the study included a lack of generalizability to younger men or women, short-term follow-up, and the use of piezoelectric sensors instead of electromyography in measuring leg movement.

By Cole Petrochko