No studies have been done to determine just how rare nightmare-induced heart attacks might be, and experts do not know whether they may result from the pulse-racing effects of the frightening dream itself, reports The New York Times.
Nightmares are more commonly seen in the rapid eye movement, or REM, phase of sleep, which gets longer as the night progresses. Therefore, nightmares are more likely to occur in the early morning hours.
Heart attacks, too, are most common in the early morning hours, when internal body clocks start secreting stress hormones and blood pressure tends to rise, said Dr. Mary Ann McLaughlin, a cardiologist at the Icahn School of Medicine at Mount Sinai in New York. If someone is at risk for a heart attack — because of high blood pressure, diabetes, sleep apnea, smoking or other factors — that attack is more likely to occur in the early morning.
But “it’s rare for an otherwise healthy person to have a nightmare that causes a heart attack,” said Dr. McLaughlin.