Is poor sleep quality harmful for the heart?

June 21, 2016 - 06:20

Serious sleep problems are associated with heart failure, but they don’t seem to impair cardiac function.

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Sleepless nights? Fortunately, they aren’t necessarily linked to a risk of heart failure. (Illustrative photo: Colourbox.)

People with insomnia have a hard time falling asleep, wake up repeatedly throughout the night and can’t fall back asleep when they wake up early in the morning. Several studies have linked insomnia to an increased risk of developing heart failure.

Weakened function of the left ventricle is among the earliest signs of heart failure, but a new study based on echocardiography examinations—a type of ultrasound—from the third Nord-Trøndelag Health Study (HUNT3) found no connection between left ventricular function and insomnia symptoms in healthy Norwegians.

“Thus, our findings don’t support a causal relationship between insomnia and heart failure,” says first author and NTNU researcher Linn Beate Strand.

Same heart function with or without insomnia

The researchers used echocardiography and survey data from a total of 788 women and men. Insomnia was defined as having at least one of the symptoms (difficulty falling asleep, frequent waking, early awakening and daytime tiredness) several times a week, and participants were categorized based on their reported number of symptoms.

Those who had insomnia symptoms were less physically active, had less education and were more often smokers or ex-smokers compared with those who had no trouble sleeping, but the left ventricular function was equally good both before and after the researchers adjusted their analyses for these differences.

Strand says, “We saw no correlation between reduced heart function and the number of insomnia symptoms. Nor was any single symptom taken on its own connected to heart function. This held true even after we eliminated the participants who stated that they snored or had sleep-related breathing problems.”

The five echocardiography measurements that researchers used in the study are well suited to detecting even small impairments in cardiac function. The researchers also excluded people from the study with known cardiovascular disease, diabetes, lung disease, cancer and high blood pressure to reduce the possibility that the sleep problems were a result of chronic disease.

Doesn’t rule out future impairment

Insomnia is about sleep quality and does not necessarily address sleep duration. Another new study links sleep duration to a risk of dying from cardiovascular disease. The researchers also stressed that the study does not say anything about how long participants had experienced insomnia symptoms, and therefore they cannot speak to what possible effects long-term sleep difficulties might have.

According to Strand, it is not inconceivable that participants with insomnia could develop impairments in the function of their left ventricle at a later date, and this needs to be investigated in future studies.

Meanwhile, researchers found a link between two of the ventricular function and insomnia measures when they expanded the definition of insomnia to include participants who reported occasional symptoms.

“It’s hard to know which of these insomnia definitions is best to use. It could be that those with insomnia symptoms several times a week do have impaired cardiac function, but that this relationship was “hidden” when we compared them to the group with only occasional symptoms and possibly with impaired cardiac function,” says Strand.

Reference:

Strand, L. B., Laugsand, L. E., Dalen, H., Vatten, L., & Janszky, I. (2016). Insomnia and left ventricular function–an echocardiography study. Scandinavian Cardiovascular Journal, 1-19.

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