Using crowdsourcing methods, we found that one out of 10 people from a large sample of 35 countries had a confirmed near-death experience (10%; 95% CI [8.5–12%]). This estimate is slightly higher than what was reported in previous studies using traditional interview-based surveys in Australia (8%) ( Perera & Padmasekara, 2005 ) and Germany (4%) ( Knoblauch, Schmied & Schnettler, 2001 ); but, of note, none of those studies validated reports with the GNDES. Experiences that did not fulfill criteria for a near-death experience were roughly twice as common in our survey.

Near-death experiences and REM sleep intrusion

Our central finding is that we confirmed a possible association of near-death experiences with REM sleep intrusion. Following multivariate analysis, REM sleep intrusion was the only factor that remained significantly correlated with near-death experiences (and indeed very much so: p = 0.0001). This finding corroborates and extends data from the previous study by Nelson and co-workers, in which the life-time prevalence of REM sleep intrusion in 55 humans with near-death experiences was compared with that in age- and sex-matched controls (Nelson et al., 2006). Sleep-related visual and auditory hallucinations and/or sleep paralysis assessed by a questionnaire like the one used in our study were substantially more common in cases with near-death experiences. The authors suggested that under circumstances of peril, near-death experiences are more likely in people with a tendency towards REM sleep intrusion and that REM sleep intrusion might explain much, if not all, of the semiology of these experiences (Nelson et al., 2006). Indeed, as shown in Table 5, two participants from our study gave spontaneous reports of classic REM sleep disturbances (rather than reporting their near-death experience as requested) akin to those seen in people with narcolepsy (Kondziella & Arlien-Soborg, 2006; Scammell, 2015).

Nelson et al. (2006) based the hypothesis of REM intrusion being associated with near-death experiences on several “lines of evidence”: REM intrusion during wakefulness occurs frequently in healthy people (from 1.2–32% for cataplexy to 24–28% for hypnagogic hallucinations (Ohayon et al., 1999; Cheyne, Rueffer & Newby-Clark, 1999)); REM intrusion is the hallmark of narcolepsy that shares semiological features with near-death experiences; and cardiorespiratory afferents may evoke REM intrusion by heightened vagal afferent activity (Nelson et al., 2006). Further, complex dream-like hallucinations like those of REM sleep are well-described with lesions near the mesopontine paramedian reticular formation and the midbrain cerebral peduncles (i.e., peduncular hallucinations) (Galetta & Prasad, 2017), suggesting that dysfunction of the REM-inhibiting serotonergic dorsal raphe nuclei and the noradrenergic locus ceruleus may facilitate REM intrusion (Hobson, McCarley & Wyzinski, 1975; Manford & Andermann, 1998; Kayama & Koyama, 2003; De Lecea, Carter & Adamantidis, 2012; Hasegawa et al., 2017). Nelson and co-workers therefore hypothesized that people with near-death experiences may have an arousal system predisposing them to REM intrusion (Nelson et al., 2006).

The anonymous nature of our online survey enabled us to avoid the selection bias that was a major point of criticism (Long & Janice Miner, 2007) of the Nelson et al. study (Nelson et al., 2006). While the latter used a case-control approach, we evaluated an unselected sample of unprimed adult lay people. We carefully adjusted for confounding factors including age, gender, place of residence, employment status and perceived danger, and we found that the association of near-death experiences and evidence for REM intrusion remained statistically highly significant. Of note, online surveys limit the influence of psychological bias as compared to face-to-face interviews or telephone surveys because there is no incentive to please the investigator by inventing or exaggerating memories (Peer et al., 2017). (There was no monetary incentive to do so either, since we instructed participants that their reimbursement was the same irrespective of whether they would report a near-death experience or not). Also, we recruited a much larger sample size than what can be achieved with lab-based behavioral testing or case-control studies, including respondents from 35 countries, which strengthens the validity and generalizability of our results. It therefore appears that the association of near-death experiences and REM intrusion is real, although future work needs to address the relationship between the two states: Does a tendency to REM intrusion predispose to near-death experiences, as Nelson et al. (2006) argue, or could it be the other way round, i.e., do near-death experiences lead to a propensity for REM sleep intrusion (Long & Janice Miner, 2007)? Either way, we suggest that characterizing the precise biological mechanisms leading to REM intrusion into wakefulness might offer new insights into the physiology of near-death experiences.