People with insomnia who take longer than 14 minutes to fall asleep have a higher risk for hypertension, new data published in Hypertension suggest.
“We observed a strong correlation between the degree of physiological hyperarousal and hypertension,” study researcher Xiangdong Tang, MD, PhD, Professor of Sleep Medicine at West China Hospital, Sichuan University in Chengdu, China, said in a press release.
“In other words, those insomniacs who were hyperalert during the day and unable to relax and fall asleep during the Multiple Latency Sleep Test (MSLT) had the higher risk of hypertension,” fellow researcher Alexandros Vgontzas, MD, Professor of Sleep Research and Treatment in the Department of Psychiatry at Pennsylvania State University College of Medicine in Hershey, said.
In the study, the researchers evaluated 219 people with chronic insomnia and 96 normal sleepers (mean age, 40 years; 60% women) from West China Hospital. Chronic insomnia was defined as difficulty sleeping for at least 6 months.
Participants were monitored in a sleep lab for 1 night. The next day, they took the MSLT, a standard measure of daytime sleepiness or alertness, which included four 20-minute nap opportunities at 2-hour intervals — 9:00 a.m., 11:00 a.m., 1:00 p.m. and 3:00 p.m.
The researchers then divided participants into four groups based on median MSLT values: normal sleepers who took longer than 14 minutes to fall asleep, normal sleepers who took 14 minutes or less to fall asleep, insomniacs who took longer than 14 minutes to fall asleep and insomniacs who took 14 minutes or less to fall asleep.
Hypertension was based on blood pressure (BP) measures or diagnosis by a physician. Researchers also controlled for confounding factors, including obesity, sleep apnea, diabetes, smoking, alcohol and caffeine use.
Results revealed that insomnia in addition to an MSLT score greater than 14 minutes increased the odds of hypertension by 300% (OR=3.27; 95% CI, 1.20-8.96). Moreover, insomnia combined with an MSLT score exceeding 17 minutes increased the odds of hypertension by 400% (OR=4.33; 95% CI, 1.48-12.68), as compared with normal sleepers with an MSLT score of 14 minutes or less.
While often considered a nighttime disorder, some research indicates that insomnia is “a disorder of physiological hyperarousal present throughout the 24-hour sleep-wake cycle,” according to background information in the study.
“Long latency times to fall asleep during the day may be a reliable index of the physiological hyperarousal and biological severity of the disorder,” Dr. Vgontzas said.
“Although insomniacs complain of fatigue and tiredness during the day, their problem is that they cannot relax and that they are hyper,” he said. “Measures that apply in sleep-deprived normal sleepers — napping, caffeine use or other stimulants to combat fatigue — do not apply in insomniacs. In fact, excessive caffeine worsens the hyperarousal.”