Why did Carrie Fisher and Debbie Reynolds die one day apart? Here’s what science can tell us

The death of actress Debbie Reynolds Wednesday night, one day after her daughter and fellow actress Carrie Fisher passed away after being stricken during a long plane flight, has sparked assorted questions among fans stunned by the timing.

Is it a coincidence that a mother would die so soon after the unexpected loss of her daughter, or could grief have played a role? Can the bond among loved ones be so tight that it’s possible to die from a broken heart? And did air travel and Fisher’s bipolar disorder diagnosis — a mental illness she has been praised for speaking out about — increase her risk of cardiac arrest.

Here’s what the science says.

Is there a connection between grief and illness?

It’s not clear yet what led to Debbie Reynolds’ death just one day after her daughter’s. But research has suggested that there’s a possible connection between grief and serious illness.

A study published in JAMA Internal Medicine in 2014 found that people who had lost a loved one in the past month were twice as likely to suffer a heart attack or stroke as their peers who weren’t grieving. It happened quite rarely, though — just 0.16 percent of those in the grieving group had a heart attack or stroke, compared to 0.08 percent in the control group. Another study, published in April 2016, found that an irregular heartbeat may also be a manifestation of emotional stress.

“Losing a loved one represents a tremendous shock to one’s system,” said Dr. David Mischoulon, a psychiatrist at Massachusetts General Hospital.

Doctors have also reported cases of stress-induced cardiomyopathy, a temporary enlargement of the heart that’s also been dubbed broken heart syndrome. It’s a temporary condition that can crop up after intense stress, whether caused by elation or sadness. It’s thought that the temporary disruption to the heart might be caused by an increase in stress hormones flooding the body. The symptoms can mimic a heart attack but in most cases, patients recover from the condition without permanent heart damage.

That shock comes from the body’s reaction to stress or trauma — what’s known as the fight or flight response. It starts in the amygdala, an almond-shaped structure in the brain that signals to the hypothalamus that there’s some type of stress or threat. That triggers the release of a slew of hormones, which ready the body’s response: Muscles tighten, heart rate speeds up, and blood flow increases.

Mischoulon recommended anyone who experiences a sudden loss check in with their primary care doctor and also consider reaching out to a therapist.

“Grief, if unchecked, can exacerbate existing medical illnesses,” Mischoulon said. “That could have some serious consequences, especially if you’re up in years.”

Does flight increase the risk of cardiac arrest?

Every year, thousands of passengers have medical emergencies in mid-air. One study, published in the New England Journal of Medicine in 2013, found that between the beginning of 2008 and the end of 2010, there were 11,920 in-flight medical emergencies among about 744 million passengers, with just over 2,800 people transferred to a hospital upon landing. People with stroke, respiratory symptoms or cardiac symptoms were most likely to be hospitalized, the study found.

Fisher apparently went into cardiac arrest, a more serious condition often mistakenly conflated with a heart attack. In cardiac arrest, the heart stops completely and must be restarted with cardiopulmonary resuscitation, said Dr. Clifton Callaway, a professor of emergency medicine at the University of Pittsburgh. A fellow passenger with medical training apparently performed CPR on Fisher. The plane was close to landing in Los Angeles, after an 11-hour trip from London, so it was not diverted to another airport.

Only 11-12 percent of cardiac arrest patients survive to leave the hospital, Callaway said. Some, like Fisher, linger for several days in the hospital before their organs give out.

There’s no indication that air travel puts more stress on the heart or increases someone’s risk for cardiac arrest, heart attack or stroke, Callaway said. “These are common diseases, they’re happening around us all the time.”

Is there a link between bipolar disorder and heart disease?

Fisher, who died four days after going into cardiac arrest, was open about her diagnosis of bipolar disorder, a mental illness characterized by extreme mood swings and compulsive behavior. While Fisher’s full medical history is not known, there’s scientific evidence for a connection between bipolar disorder and cardiac arrest.

People with psychiatric disorders have a shorter lifespan overall, due in part to a greater-than-average susceptibility to heart disease. A study from Denmark found a physiological relationship between the two conditions, with bipolar disorder affecting the heart in significant ways. Patients with bipolar disorder had lower heart-rate variability than people without the condition.

Time intervals between a person’s beats — their heart rate — usually vary depending on factors such as stress and physical activity. Most people have lower heart rates when sitting at home than when exercising or running errands. High variability between those rates is ideal; low variability is indicative of greater stress and reduced physical resiliency.

“People with high heart-rate variability are people with emotional stability and more of an ability to cope, whereas people with bipolar disorder don’t have that,” said Dr. Helen Farrell, a psychiatry professor at Harvard who was not involved with the research.

But not all experts are convinced there’s such a direct connection. Dr. Mark Link, a cardiologist at the University of Texas Southwestern Medical Center, said cardiologists aren’t convinced the connection between heart-rate variability and bipolar disorder is so clear-cut.

“It’s largely thought among cardiologists that it’s not bipolar disorder but the treatment of it,” he said. “Certain antidepressants and anti-psychotic meds increase the QT interval,” the time the heart muscle takes to recharge between beats, “and increase the risk for sudden death.”