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No, cardiac arrests are not more common on Monday mornings, study finds

EKG machine
REUTERS/Ivan Alvarado
An analysis of the timing of the 1,535 deaths identified in the current study revealed no early morning peak in sudden cardiac arrests.

People are not at greater risk of dying from sudden cardiac arrest in the morning — including Monday morning — than at other times of the day, according to a study published recently in the journal Heart Rhythm.

This finding calls into question the long-standing belief — bolstered by several previous studies — that the morning hours present a kind of “danger time zone” for life-threatening heart-related events, such as heart attacks, stroke and sudden cardiac arrest.

One possible explanation for the new finding may be due to “the advent of the internet and smart phones, allowing for access to entertainment, social life, and even work activities 24 hours a day, 7 days a week,” the current study’s authors point out.

In other words, the morning hours are no longer the only time when the pressures or excitements of daily life cause blood vessels to narrow and the heart to beat faster.

“While there are likely several reasons to explain why more cardiac arrests happen outside of previously identified peak times, stress is likely a major factor,” explains Dr. Sumeet Chugh, the study’s senior author and a cardiologist at the Cedars-Sinai Medical Center in Los Angeles, in a released statement.

“We now live in a fast-paced, ‘always on’ era that causes increased psycho-social stress and possibly, an increase in the likelihood of sudden cardiac arrest,” he adds.

More than a decade of data

For the study, Chugh and his colleagues used 2002-2014 data from the Oregon Sudden Unexpected Death Study, an ongoing research project that is tracking sudden unexpected deaths that occur outside of hospitals in the Portland metropolitan area. The data included not only the cause of each death, but the time of each death as well.

The researchers identified 2,631 adult deaths from sudden cardiac arrest within that database. To ensure that the times of those deaths were accurate, however, they included for analysis only the 1,535 sudden cardiac arrest deaths that had been witnessed by bystanders or emergency personnel. (By examining only the witnessed deaths, this study differentiated itself from earlier ones.)

Sudden cardiac arrest is not the same as a heart attack (myocardial infarction). As the American Heart Association (AHA) explains on its website, “A heart attack is when blood flow to the heart is blocked, and sudden cardiac arrest is when the heart malfunctions and suddenly stops beating unexpectedly.”

“A heart attack is a ‘circulation’ problem and sudden cardiac arrest is an ‘electrical’ problem,” the organization adds.

A person who has sudden cardiac arrest will die within minutes if not treated with cardiopulmonary resuscitation (CPR) and defibrillation. Each year, the condition kills almost 600,000 Americans, making it the third-leading cause of death behind cancer and heart disease. Four out of five sudden cardiac arrests occur in the home, and more than 90 percent of those individuals die before they reach the hospital.

Key findings

An analysis of the timing of the 1,535 deaths identified in the current study revealed no early morning peak in sudden cardiac arrests. It found, instead, that the death rate from cardiac arrests was lowest between midnight and 6 a.m. (13.9 percent) and then held relatively steady throughout the rest of the day.

The morning (6 a.m. to noon) rate was 27.6 percent; the afternoon (noon to 6 p.m.) rate was 31.6 percent; and the evening (6 p.m. to midnight) rate was 26.9 percent.

Nor did the data reveal Monday to be a particularly dangerous day. In fact, the only day of the week that stood out was Sunday, when the death rate from sudden cardiac arrest reached its weekly nadir: 11.3 percent.

The study’s findings held even after the data was adjusted for age, gender and existing heart disease.

Only one piece of the puzzle

This study examined only deaths from sudden cardiac arrest. It did not look at deaths from other sudden cardiovascular events, such as heart attacks and strokes.

Also, the researchers did not have access to data on the sleep-wake cycles, work hours, weekend activities and other lifestyle habits of the individuals who died of sudden cardiac arrest in their study. So they are unable to determine why this study — unlike most previous ones — found no link between time of day and risk of sudden cardiac arrest.

The researchers do point out, however, that several small studies, including ones from Spain and Tunisia, have recently reported findings similar to theirs.

“This is just another piece to the puzzle,” says Chugh. “Our next steps are to conclusively determine the underlying reasons behind this shift, then identify public health implications as a result.”

“Because sudden cardiac arrest is usually fatal, we have to prevent it before it strikes,” he stresses.

FMI: You’ll find an abstract of the study on the Heart Rhythm website, but the full study is behind a paywall.

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