Insomnia, Short Sleep Linked to Greater Risk for MI

Those who slept 5 or fewer hours per night had the highest risk for MI, and those with both diabetes and insomnia had double the risk for MI compared with patients without these comorbidities. The findings are from a meta-analysis of studies studies in more than 1 million patients, almost all without prior MI who were, on average, in their early 50s and followed for 9 years.

"Insomnia and ≤ 5 hours of sleep are highly associated with increased incidence of MI, an association comparable to that of other MI risk factors and as such, it should be considered as a risk factor for MI and to be incorporated into MI prevention guidelines," the researchers conclude.

"We believe that [insomnia] should be screened and patients should be educated about the importance of sleep because nowadays insomnia is no longer a disease — sleep deprivation could also be a life choice," Dean told a press conference prior to the meeting later this week.

"Clinicians must educate the patients about the importance of sleep in maintaining a healthy heart and encourage proper sleep hygiene," Dean reiterated in an email to | Medscape Cardiology.

"And if a patient still has insomnia, other methods should be considered such as cognitive behavior therapy for insomnia (CBT-I)."

Adds to Growing Evidence

This study does not allow any conclusion about whether treating insomnia will reduce heart attack risk, Jennifer L. Martin, PhD, president of the American Academy of Sleep Medicine (AASM), noted in an email to | Medscape Cardiology. Nor does it report the diversity of study participants, since insomnia is also a health equity issue, she noted, and insomnia symptoms and comorbidities were self-reported.

However, this analysis "adds to the growing evidence that poor quality or insufficient sleep is associated with poor health," said Martin, professor of medicine at UCLA's David Geffen School of Medicine, Los Angeles, who was not involved with this research.

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The study reinforces the recommendation from the American Heart Association, which includes "Get Healthy Sleep" as one of “Life's Essential 8” for heart health, Martin noted.

"Particularly in primary care where disease prevention and health promotion are important, clinicians should be asking all patients about their sleep — just like they ask about diet and exercise — as a key aspect of maintaining heart health," she said.

Advice about basic sleep hygiene advice is a first step, she noted.

When improved sleep hygiene is not enough to address chronic insomnia, the American Academy of Sleep Medicine's clinical practice guidelines and the guidelines of the VA/Department of Defense, recommend first-line treatment with CBT-I, typically offered by a sleep specialist or mental health clinician.

Similarly, the American College of Physicians suggests that sleeping pills should be reserved for short-term use in patients who may not benefit sufficiently from CBT-I.

Sleeping Too Little, Too Much, Equally Harmful

"Studies have found that insomnia and subsequent sleep deprivation puts the body under stress," Dean said. "This triggers cortisol release which could accelerate atherosclerosis," and increase risk of MI.

For this analysis, the researchers identified nine observational studies, published from 1998 to 2019, with data on incident MI in adults who had insomnia.

The diagnosis of insomnia was based on ICD diagnostic codes or on the DSM‐5, which defines insomnia as the presence of any of the following three symptoms: difficulty initiating sleep, difficulty maintaining sleep, or early morning awakening with inability to return to sleep.

Patients with sleep apnea were excluded.

The studies were in populations in China, Germany, Norway, Taiwan, United Kingdom, and United States, in 1.1 million adults aged 18 and older.

The patients had a mean age of 52 years and 13% had insomnia.

During follow-up, 2406 of 153,881 patients with insomnia, and 12,398 of 1,030,375 patients without insomnia had an MI.

In the pooled analysis, patients with insomnia had a significantly increased risk of MI (relative risk [RR] 1.69, P < .00001), after adjusting for age, gender, diabetes, hypertension, high cholesterol, and smoking.

Sleeping 5 hours or less was associated with a greater risk for MI than sleeping 6 hours, or 7-8 hours, but sleeping 9 hours or more was just as harmful.

Table. Risk for MI with Different Sleep Durations

Sleep Durations (hours/night)Relative Risk for MIP value
≤ 5 vs 6 1.38 < .00001
≤ 5 vs 7-8 1.56 < .00001
≤ 5 vs ≥ 9 1.04 .57
6 vs 7-8 1.14 .0002
6 vs ≥ 9 0.75 < .00001
7-8 vs ≥ 9 0.67 .67

Patients who had difficulty initiating and maintaining sleep — two symptoms of insomnia — had a 13% increased risk for MI compared with other patients (RR = 1.13, = .003).

However, patients who had nonrestorative sleep and daytime dysfunction despite adequate sleep — which is common — did not have an increased risk of MI compared with other patients (RR = 1.06, P = .46). 

Women with insomnia had a 2.24-fold greater risk for MI than other women, whereas men with insomnia had a 2.03-fold greater risk for MI than other men. 

Patients with insomnia had a greater risk for MI than those without insomnia in subgroups based on patients' age (< 65 and > 65), follow up duration (≤ 5 years and > 5 years), and co-morbidities (diabetes, hypertension, and hyperlipidemia).