Poor Sleep May Hike Mortality in Metabolic Syndrome

Highest risk in those with high blood pressure, poor glucose metabolism

Short sleep duration was associated with increased risk of mortality among people with a cluster of cardiovascular risk factors known as metabolic syndrome, according to an observational study.[[{"type":"media","view_mode":"media_crop","fid":"60650","attributes":{"alt":"","class":"media-image media-image-right","id":"media_crop_8899892451838","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"7667","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"height: 153px; width: 215px; border-width: 0px; border-style: solid; margin: 5px; float: right;","title":" ","typeof":"foaf:Image"}}]]

Among more than 1300 adults who spent the night in a sleep lab, those with metabolic syndrome who slept 6 or more hours were more likely to die of cardiovascular disease (HR 1.49, 95% CI 0.75-2.97) during the 16.6-year follow-up period than people without metabolic syndrome, reported Julio Fernandez-Mendoza, PhD, of the Penn State Hershey Sleep Research & Treatment Center, and colleagues.

People who slept less than 6 hours were more likely to die of heart disease or stroke (HR 2.10, 95% CI 1.39- 3.16), as well as from any cause (HR 1.99 times, 95% CI 1.53-2.59), compared with those without metabolic syndrome, the researchers wrote online in the Journal of the American Heart Association.

The researchers noted that the relationship was seen even after adjusting for sleep apnea, a known heart disease risk.

“Sleep should be evaluated and taken into consideration when calculating cardiovascular risk, especially in those who have already developed cardiometabolic risk factors,” Fernandez-Mendoza told MedPage Today via email.

“For clinicians, the implications are to always question their patients about their sleep beyond sleep apnea and refer to a sleep clinic if there is a suspicion of a sleep disorder or sleep of less than 6 hours in duration. For the public, [the implications are] to take care of their sleep and consult with their clinicians, particularly if they already have the metabolic syndrome or any of its risk factors (obesity, high blood pressure, or glucose, etc.).”

Wendy Troxel, PhD, senior behavioral and social scientist at RAND Corporation, who was not involved in the study, also commented on the implications: “This suggests the possibility that sleep-focused interventions which seek to extend sleep duration could have a positive impact on cardiovascular health and reduce mortality risk.”

For the study, Fernandez-Mendoza and colleagues randomly selected 16,583 men and women from the Penn State Adult Cohort to participate in a telephone interview on their history of sleep difficulty, heart disease, stroke, daily consumption of caffeine, and tobacco use, among other things.

During the second phase of the study, 741 men and 1000 women were randomly selected from the first phase to spend 1 night in the sleep laboratory, where they were continuously monitored for 8 hours using 16-channel polysomnography, including electroencephalogram, electrooculogram, and electromyogram.

Metabolic syndrome was defined by the presence of 3 or more of the following risk factors: obesity (≥30 kg/m²), elevated total cholesterol (≥200 mg/dL), triglycerides (≥150 mg/dL), fasting glucose (≥100 mg/dL), and blood pressure (≥130/85 mm Hg).

Blood pressure was measured in the evening, around 2 hours before the start of the sleep recording, using a pneumoelectric microprocessor-controlled instrument.

The researchers used Cox proportional hazard models, controlling for multiple potential confounders, to test the interaction between metabolic syndrome and polysomnographic sleep duration on mortality.

Over a follow-up period of 16.6 years, the team found that 39.2% of the final 1344 participants had at least 3 of the risk factors for metabolic syndrome.

Those with metabolic syndrome showed a significantly higher crude mortality rate than those without metabolic syndrome (32.7% versus 15.1%; P<0.01). People with metabolic syndrome also showed a 2-fold higher risk of all-cause mortality (HR 1.73; 95% CI 1.40 to 2.14) and cardiovascular disease/cerebrovascular mortality (HR 1.92; 95% CI 1.35 to 2.74) compared with those without metabolic syndrome after adjusting for all covariates (ie, age, race, sex, smoking, alcohol use, depression, insomnia, heart disease, and stroke).

Compared with in the reference group, the risk of all-cause mortality was significantly increased in those with metabolic syndrome clusters of:

• Elevated blood pressure and 2 or 3 other components, but without elevated fasting glucose (HR 1.75; 95% CI 1.16-2.64)

• Elevated fasting glucose and blood pressure with 1 or 2 other components (HR 1.46; 95% CI 0.96-2.32)

• Both fasting glucose and blood pressure elevated (HR 1.76; 95% CI 1.40-2.22)

On average, participants with metabolic syndrome slept half an hour less than those without metabolic syndrome, and objective short sleep duration was associated with all 5 cardiometabolic components (P<0.05).

Limitations of the study, the researchers said, included the observational nature, as well as the use of only 1 day of sleep lab results and the small number of minority patients.

Fernandez-Mendoza noted that while there are well-established behavioral and pharmacological approaches to effectively treat sleep disorders, this study indicated that future clinical trials should examine whether targeting sleep in parallel with decreasing blood pressure and glucose levels would further improve the prognosis of people with metabolic syndrome.

“In other words, whether they get better and are less likely to develop complications, that would ultimately lead to early death. Sleep in the context of metabolic syndrome should be seen as an added and modifiable risk factor,” he explained.

Troxel agreed about the need for future studies, and said they should “look beyond sleep duration and consider other sleep disturbances, such as poor sleep quality or insomnia as effect modifiers of metabolic syndrome on mortality risk.”

The study was supported by the American Heart Association and the National Institutes of Health.

The authors noted having no disclosures to report.

last updated 05.26.2017

Primary Source: Journal of the American Heart Association

Fernandez-Mendoza J, et al. “Impact of the metabolic syndrome on mortality is modified by objective short sleep duration.” J Am Heart Assoc. 2017; DOI: 10.1161/JAHA. 117.005479.

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