Irregular sleep can lead to increased heart attack risk


It’s easy to forget how many confounding elements contribute to quality sleep. We know how material duration is to the equation but a new paper emphasizes the importance of consistency.

The five-year-long, multi-ethnic study published in the Journal of the American College of Cardiology concluded that an irregular sleep pattern dramatically surges one’s risk of experiencing a heart attack later in life.

For all medical intents and purposes, irregular” was defined as a 30-minute difference in either direction over the course of seven nights. Even after outcomes were adjusted to reflect relevant correlates like  blood pressure, cholesterol, and pre-existing cardiovascular diseases (CVD), irregular sleep time that exceeded 80 minutes posed a profound risk increase. This prerequisite effectively highlights sleep consistency as an independent health predictor.

Even without isolating sleep quality, one out of every three deaths that occur within the US is proceeded by a fatal cardiovascular event and 60% of Americans will experience a heart attack at some point in their lifetime.

“Compared with people who had the most regular sleep time, those with the most irregular sleep time — more than a 90-minute difference on average across seven nights — had more than a two-fold increased risk of cardiovascular disease over a 5-year period,” explained study author Tianyi Huang, an assistant professor of medicine at Harvard Medical School.

Circadian balance

The research began with a study pool comprised of 1,992 American individuals between the ages of 45 and 84 with no prior history of cardiovascular diseases.  Roughly 38% were white, 28% identified as  African American, 22% identified as Hispanic, and 12%  identified as Chinese American.  Each participant was fitted with an actigraph device  that measured their sleep seven for consecutive days a week.

By using a baseline questionnaire the researchers were able to document lifestyle and disease changes over the course of the five year study period.

Roughly 25% of the recruitment evidenced irregular sleep schedules. Followup tests found the trend to negatively contribute to heart beat, vascular tone and blood pressure. The longer participants disturbed their circadian clock the more they increased their likelihood of experiencing a heart attack.

Moreover, inconsistent wakeful times were also associated with obesity and a slew of metabolic disease, including diabetes.

By the end of the study period 111 participants either developed CVD events or died as a result of a heart attack or stroke. Irregular sleep patterns that amounted to 90 minutes in either direction over the course of seven days nearly doubled one’s risk for the aforementioned outcomes. Of the demographics studied, minorities evidenced the highest instances of irregular sleep patterns.

“This sleep irregularity may be even more common among younger people,” Huang said in a press statement. “Younger people may have more demands from study and from work, and those may also influence whether they can have a regular sleep pattern or not.”

Haung intends to locate specific bio blood markers to better establish the correlation posited in the new paper.

Just this week a team of researchers from the University of Stanford determined that persistent drowsiness potentially indicates increased cancer, diabetes,  and high-blood pressure risk. More intimately,  hypersomnolence, or excessive day-time sleepiness, has an enormous impact on productivity, social interactions and the presence of mood disorders.

“Research has linked irregular sleep schedules to a constellation of disease-causing abnormalities in body function, including changes in blood sugar and inflammation,” said Michael Twery, Ph.D., director of the NHLBI’s National Center on Sleep Disorders Research. “This study is Important because it is among the largest of its kind, and it specifically associates these irregular sleep patterns with an increased risk for cardiovascular disease.”

The new report was co-authored by Tianyi Huang, Susan Redline, M.D., MPH, a senior physician in the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital, and Sara Mariani, Ph.D., formerly with Brigham and Women’s.