New research, published in the journal Heart Rhythm, discovers that due to recent cultural shifts in our work schedules and daily stressors, sudden cardiac arrests no longer tend to occur in the mornings.

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Sudden cardiac arrest can occur any time of the day, says a new study.

Until now, the consensus has been that a range of cardiovascular events, such as angina, heart attacks, and stroke, tend to happen mostly in the early hours of the morning.

A possible explanation for this phenomenon is that in the morning, the sudden pressures of daily activities put a strain on people's cardiovascular system.

Just waking up, in fact, releases the activity of certain hormones, such as cortisol, that raise blood pressure, heart rate, and glucose levels, as well as narrow blood vessels and prompt our hearts to pump harder.

However, given the new pressures of modern life — such as instant communication, the prevalence of smartphones, apps, and the online medium in general — the timing of our daily stressors may have changed.

So, do these changes have a bearing on certain cardiovascular events and the time of day in which they occur? New research suggests so.

Zooming in on sudden cardiac arrests

Scientists from the Cedars-Sinai Medical Center in Los Angeles, CA — led by Dr. Sumeet Chugh, a professor of medicine — set out to investigate when the peak times for sudden cardiac arrests during the day are.

As Dr. Chugh and team explain, contrary to popular belief, sudden cardiac arrest is quite different to a heart attack. Unlike in a heart attack, during sudden cardiac arrest, the heart stops beating suddenly. Death occurs if medical assistance is not given within minutes.

A heart attack, on the other hand, occurs when blood flow to the heart is partially blocked, which does not usually cause the heart to stop beating.

As the study authors mention, around half of all cardiovascular deaths in the United States result from sudden cardiac arrest, and up to 350,000 cases occur each year, making the condition a significant concern for public health.

'Stress is likely a major factor'

Dr. Chugh and his team studied data available from the Oregon Sudden Unexpected Death Study, which began in 2002.

For the analysis, the investigators looked at the data collected from emergency medical reports in 2004–2014. During this time, 1,535 adults had sudden cardiac arrests and died as a result.

Of these people, note the authors, only 13.9 percent died between 12 a.m. and 6 a.m. Contrary to older research and an ensuing widespread belief, the study found no evidence of a higher prevalence of sudden cardiac arrests on Mondays.

"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. Chugh.

"Because sudden cardiac arrest is usually fatal, we have to prevent it before it strikes," he adds.

"We now live in a fast-paced, 'always on' era that causes increased psychosocial stress and possibly, an increase in the likelihood of sudden cardiac arrest."

Dr. Sumeet Chugh

Dr. Chugh also shares some directions for future research, explaining, "Our next steps are to conclusively determine the underlying reasons behind this shift, then identify public health implications as a result."