Insomnia With Daytime Hyperarousal Linked to Hypertension

January 29, 2015

Further evidence that insomnia itself — without sleep apnea — is associated with the development of hypertension has come from a new study.

The study, published online in Hypertension on January 26, shows that insomnia is often associated with hyperarousal, that is, being unable to relax and fall asleep during the day as well as at night, and that this is linked to the development of hypertension.

"Previous studies have found that lack of sleep at night is associated with increased cortisol levels and hypertension but this is the first study to connect hyperarousal during the day with hypertension," coauthor Alexandros Vgontzas, MD, professor of sleep research, Pennsylvania State University College of Medicine, Hershey, commented to Medscape Medical News.

"It is important for doctors to take insomnia seriously. While sleep apnea is recognized to cause hypertension, insomnia is regarded as the poor relation in medical terms. This needs to be changed as insomnia itself also likely causes cardiovascular problems, especially if associated with hyperarousal," he added.

Hyperarousal Requires Different Treatment

Several studies have shown that insomnia is associated with increased resting heart rate, impaired heart rate variability, higher metabolic rate, higher body temperature, activation of the hypothalamic-pituitary-adrenal axis, and increased beta electroencephalography activity and brain metabolic rate compared with normal sleepers, the authors write. These findings suggest that insomnia is a disorder of physiologic hyperarousal present throughout the 24-hour sleep-wake cycle.

The researchers point out that it is important to identify these hyperaroused individuals because they may need different approaches to the treatment of their insomnia.

"Although hyperaroused insomniacs complain of fatigue and tiredness during the day, their problem is that they cannot relax," Dr Vgontzas said. "Measures often used to combat fatigue, such as drinking coffee or using other stimulants, are not appropriate in these individuals that would worsen the hyperarousal.

"Insomniacs who have hyperarousal during the day as well as at night have a 24-hour disorder, so they need a 24-hour treatment aimed at reducing this hyperarousal, not just a hypnotic pill with a short half-life given at night, which is the traditional prescribing practice.

"They need a more general approach, which could include relaxation techniques to reduce physiological hyperarousal throughout the whole 24 hour period. If medication is to be used, this should be directed at downregulating the cortisol system or anxiolytics if major anxiety is present," Dr Vgontzas suggested.

The study, conducted at West China Hospital, Sichuan University, Chengdu, involved 219 patients with chronic insomnia and 96 normal sleepers (average age, 40 years; 605 women). Chronic insomnia was defined as a greater than 6-month history of difficulty sleeping.

Multiple Sleep Latency Test

The participants spent one night monitored in a sleep laboratory and were monitored for daytime hyperarousal the next day by using the Multiple Sleep Latency Test (MSLT). This involved four 20-minute nap opportunities at 2-hour intervals.

The test involves putting individuals into a dark, relaxing environment and encouraging them to fall asleep. If they fall asleep quickly they are said to have short sleep latency.

Dr Vgontzas explained: "It may be expected that someone has trouble sleeping at night would be sleepy during the day and fall asleep quickly under such conditions, but many insomniacs actually show the opposite effect — being unable to fall asleep easily during the day or night. These people are labeled as hyperaroused."

In the current study the average MSLT score (time taken to fall asleep) was 14 minutes. Those who took more than 14 minutes to fall asleep were considered hyperaroused.

Hypertension was based on blood pressure measures or a physician's diagnosis. After adjustment for confounding factors, such as obesity, sleep apnea, diabetes, smoking, alcohol, and caffeine use, chronic insomnia combined with an MSLT score greater than 14 minutes increased the risk for hypertension more than 3 times that the risk in controls (odds ratio [OR], 3.27; 95% confidence interval [CI], 1.20 - 8.96) and MSLT scores greater than 17 minutes increased the risk more than 4 times (OR, 4.33; 95% CI, 1.48 - 12.68).

"So we found a dose response," Dr Vgontzas said.

In the paper, the researchers point out that conducting MSLTs on all patients with insomnia would be costly and impractical, so other simpler methods, such as pupillometry or measures of peripheral sympathetic activation, need to be tested and validated for measuring physiologic hyperarousal.

This study was funded by the National Natural Science Foundation of China, the Chinese German Joint Center for Sleep Medicine, the National Basic Research Program of China, and National Government Building High-level University Graduate Programs. The authors have disclosed no relevant financial relationships.

Hypertension. Published online January 26, 2015. Abstract


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