Kevin Nelson’s study of near-death experiences and sleep: 55 people and four questions

Step 1

Before 2006 · The question

Some people have an NDE and others don’t, and no one knew why

By the early 2000s, three studies had been done with people resuscitated after a cardiac arrest. A cardiac arrest is when the heart stops pumping. In those studies, between 6 and 12 in 100 people described an NDE. One of them was done by the cardiologist Pim van Lommel in ten hospitals in the Netherlands. We cover it in the van Lommel study.

Those studies looked for what set the people with an NDE apart. They found nothing clear. It didn’t depend on the drugs they were given, on how long the cardiac arrest lasted, or on how they were resuscitated.

So one question remained open. If many people go through the same thing, why do only some of them have an NDE?

A neurologist in Kentucky thought the answer might lie in sleep.

Step 2

2005 · University of Kentucky · As the study tells it

Kevin Nelson sees similarities between the NDE and the stage of sleep in which we dream

Kevin Nelson is a neurologist at the University of Kentucky, in the United States. He did the study with three researchers from the same university.

To understand his idea, you need to know what REM sleep is. It is the stage of sleep in which we dream. REM stands for “rapid eye movement,” because the eyes move a lot under the eyelids. In this stage the brain is very active. The body, on the other hand, goes limp, so that the arms and legs don’t move while we dream.

Sometimes, bits of this stage slip in when the person is already awake or nearly awake. Doctors call this REM sleep intrusion. A person may see or hear things that aren’t there as they fall asleep or wake up. And they may wake up unable to move for a few seconds. This is called sleep paralysis.

Nelson saw similarities between this stage and some NDEs. Many NDEs include a very bright light. In some, the person lies still, unable to move, is aware of what is going on around them, and feels they have died. For Nelson, that light and being unable to move are reminiscent of REM sleep.

Before doing his own study, he gathered what others had already written about sleep.

Step 3

2006 · The review · As the study tells it

Four of his five reasons come from other people’s studies, in healthy people, in patients, and in animals

The article gives five reasons for its idea. The first four come from other people’s studies:

• Bits of REM sleep happen to many healthy people. In a survey of nearly 14,000 Europeans, 6 in 100 said they had had sleep paralysis at some point. In other large surveys, between 24 and 28 in 100 people said they had seen or heard things as they fell asleep.
• Bits of REM sleep lie behind some illnesses. It happens often in narcolepsy, an illness in which the person suddenly falls asleep during the day. And some studies link it to the visions of some people with Parkinson’s disease and of some people in severe alcohol withdrawal.
• It could explain parts of the NDE. According to the article, the light, seeing oneself from outside the body, and the peace all have something similar in REM sleep or in fainting. The authors themselves write that NDEs and dreams are very different. An NDE is remembered as something very real and lacks the absurdity of dreams.
• A body in danger can trigger it. In experiments with animals, stimulating the vagus nerve triggered the REM stage. The vagus nerve is the nerve that carries signals from the heart and lungs to the brain. In serious danger, this nerve is very active.

These four reasons support the idea that it is possible. None was measured in a person during an NDE.

The fifth reason was the only one the team measured on its own.

Step 4

Before 2006 · The interviews · As the study tells it

They interview 55 people with an NDE and 55 people without one

The team found the people with an NDE on a website called NDERF, the Near Death Experience Research Foundation. It was founded by the physician Jeffrey Long, and thousands of people have written about their experience there. The study thanks Long for helping to find the participants.

They wrote to 446 people from that website. Sixty-four people from North America replied. The team interviewed 55. All of them had been in serious danger, and their experience scored 7 points or more on the Greyson scale. This scale is a 16-question questionnaire that researchers use to decide whether an experience is an NDE. They left out 9 people. Three didn’t reach 7 points, and six had not been in imminent danger.

The 55 had had their NDE in very different situations. Ten had it while fainting or nearly fainting in a dangerous situation. Eight had a heart problem, eight nearly drowned, and eight were in a car accident. The rest had it after a blow to the head, during surgery, during a stroke, and in other situations.

They were compared with another 55 people of the same age and sex. These were staff at the university’s medical center, or people they knew. The study does not say whether any of them had been through a similar danger.

Everyone was asked the same four questions, in an interview. The first three are about bits of sleep. The fourth is about something that happens a lot in narcolepsy.

• Have you ever, just before falling asleep or just after waking up, seen things or people that others can’t see?
• Have you ever, at those moments, heard sounds, music, or voices that others can’t hear?
• Have you ever woken up unable to move?
• Have you ever felt your legs suddenly give way when laughing, getting emotional, or getting scared?

The questions covered the person’s whole life. They didn’t ask when each thing had happened. And no one measured anyone’s sleep in a laboratory.

The answers from the two groups came out very differently.

Step 5

2006 · The results · As the study tells it

33 of the 55 people with an NDE said yes, and 13 of the 55 people without one

The people with an NDE answered yes much more often:

• Seeing things when falling asleep or waking up: 23 of the 55 with an NDE, and 4 of the 55 without one.
• Hearing things at those moments: 20 with an NDE, and 4 without one.
• Waking up unable to move: 25 with an NDE, and 7 without one.
• Legs suddenly giving way: 4 with an NDE, and none without one. This difference is so small that it could be chance.

In total, 33 of the 55 people with an NDE said yes to one question or more. That is 60 in 100. In the other group, 13 of the 55 said yes. That is about 24 in 100. Also, the people with an NDE tended to say yes to several questions. In the other group, almost all said yes to only one.

The team found something else. Some people with an NDE had heard things as they fell asleep or woke up. According to the Greyson scale, their NDE was more intense than that of the other people with an NDE.

What was measured are yes-or-no answers, from memory, about the person’s whole life. The authors call them REM sleep intrusion, but none was checked in a sleep laboratory.

With these data, the team put forward its explanation.

Step 6

April 2006 · The conclusion · As the study tells it

The authors think some people have a brain that slips into sleep easily

The brain has a system that decides when we are awake and when we are asleep. The authors call it the arousal system. According to Nelson, in some people this system easily lets bits of REM sleep through. When these people are in danger of dying, they would be more likely to have an NDE.

The authors word it carefully. This is their conclusion:

“REM intrusion may underlie some of the subjective experiences of NDE and syncope.”

Syncope is the medical word for fainting. They acknowledge that their study is preliminary. The people volunteered themselves, and they answered from memory about their past. They propose following patients who have a cardiac arrest. According to their idea, those who already had those bits of sleep beforehand would have more NDEs.

They also acknowledge a problem in testing it. When the brain gets too little blood, its waves become slow and large. Those waves would hide the REM waves in a recording of the brain. That is why it would be very hard to see the REM stage during a cardiac arrest.

The following year, the same team published another article in the same journal. It proposed that the feeling of leaving the body is also linked to the arousal system.

The reply came from the very website where the participants had been found.

Step 7

2007 · As the critics tell it

Long and Holden reply that no one knows whether those bits of sleep came before or after the NDE

Jeffrey Long is the physician who founded the NDERF website, where the participants came from. Janice Miner Holden is a professor of counseling at the University of North Texas. Both have led the International Association for Near-Death Studies, known as IANDS. Long was its director, and Holden its president. They published their reply in that association’s journal.

They begin by acknowledging that Nelson’s idea is possible and deserves study. Then they give their reasons against the study. These are the main ones:

• The order. The questions say “ever.” According to Long, people write on NDERF on average about 15 years after their NDE. Over so much time, those bits of sleep could have started after the NDE, as one of its consequences. In that case they would not be what causes it.
• The answers. In their view, a yes may not be REM sleep. After an NDE, many people describe visions as they fall asleep or wake up that need not be bits of sleep. The team didn’t write down what each person described when they said yes.
• The comparison group. The people without an NDE were not chosen from among people who had been in danger of dying. Someone who survives something like that may sleep worse, whether or not they had an NDE. Long and Holden point out that sleep paralysis is more common in people with post-traumatic stress.
• How rarely the other group said yes. Only 4 of the 55 people in the other group said they had seen things as they fell asleep or woke up. That is about 7 in 100. Nelson’s own article cites a study in which 19 in 100 healthy people say so. For Long and Holden, health care workers may not want to admit to something that sounds like an illness.
• Those who said no to everything. Of the 55 people with an NDE, 22 said no to all four questions. That is 40 in 100. For Long and Holden, this means that many NDEs happen without those bits of sleep.
• NDEs under anesthesia. There are NDEs under general anesthesia and with drugs that suppress the REM stage. For Long and Holden, if that stage is suppressed, it is unlikely to be what produces the NDE.
• People blind from birth. According to them, they don’t see in their dreams, and yet some say they saw during their NDE. We cover this in the Ring and Cooper study.
• How different the NDE is. For them, NDEs are very much alike and change the lives of those who have them. Dreams and bits of sleep don’t.

Long and Holden propose the same kind of study as Nelson. Ask many patients when they are admitted to hospital, before any cardiac arrest. Then compare three groups: those who have a cardiac arrest with an NDE, those who have a cardiac arrest without an NDE, and those who have no cardiac arrest at all.

That study has not been done. Twelve years later, another team asked the same questions to many more people.

Step 8

2019 and 2025 · What came next

A survey of 1,034 people in 35 countries finds the same thing, with the same limit

In 2019, the neurologist Daniel Kondziella, from the University of Copenhagen, and two colleagues asked Nelson’s four questions again. They did it online, on a website that pays people to answer surveys. 1,034 people in 35 countries responded. They knew the survey was about NDEs.

Of these people, 106 described an experience that reached 7 points on the Greyson scale. Almost half of them, 50 of the 106, said yes to three or more of the four questions. Among the people who described no similar experience, 14 in 100 did. We cover it in the Kondziella survey.

Kondziella and his colleagues write that the link between the two seems real. They also write that they didn’t ask what came first. So they don’t know whether bits of sleep lead to the NDE or the NDE leads to bits of sleep.

In 2025, Nelson and Kondziella co-authored the NEPTUNE model with researchers from the University of Liège, in Belgium. It is an attempt to explain NDEs through the brain, and REM sleep is one of its pieces. That same year, the psychiatrist Bruce Greyson and the researcher Marieta Pehlivanova replied to it. On sleep, they cite a 2004 study that recorded the sleep of people with an NDE. According to them, these people took longer to enter the REM stage and had fewer REM stages than others. They add that bits of sleep usually come with distress and fear, as in sleep paralysis.

The question from the beginning remains: does the brain of someone who has an NDE mix sleep and waking? Let’s look at what is known and what isn’t.