In older adults with cardiogenic out-of-hospital cardiac arrest, the no-flow time window compatible with an estimated probability of at least 1% for favorable neurologic outcome became progressively shorter with advancing age.
Key Findings
Results
Among all older adults (65 years or older) with cardiogenic OHCA, the no-flow time threshold at which the estimated probability of favorable neurologic outcome fell below 1% was 11 minutes.
No-flow time was defined as the interval from witnessed arrest to initiation of CPR by EMS clinicians.
The threshold was 11 (95% CI, 11-11) minutes for all patients aged 65 years or older.
Favorable neurologic outcome was defined as cerebral performance category of 1 or 2 at 30 days.
Overall, only 8,711 patients (3.4%) achieved a 30-day favorable neurologic outcome across the entire cohort.
Results
The no-flow time threshold for at least 1% probability of favorable neurologic outcome decreased progressively with each older age stratum.
For patients aged 65 to 74 years, the threshold was 14 (95% CI, 14-14) minutes.
For patients aged 75 to 84 years, the threshold was 11 (95% CI, 10-11) minutes.
For patients aged 85 to 94 years, the threshold was 2 (IQR, 0-4) minutes.
For patients aged 95 years or older, the threshold was 0 (95% CI, 0-0) minutes, indicating virtually no window for favorable outcome.
Methods
The study included 259,851 older adult patients with witnessed cardiogenic OHCA drawn from a large nationwide registry spanning 14 years.
Data were sourced from the All-Japan Utstein Registry from January 1, 2010, through December 31, 2023.
Among 1,795,502 total registry cases, 259,851 patients met inclusion criteria (adults 65 years or older with witnessed cardiogenic OHCA treated by Japan's nationwide EMS system).
The median patient age was 82 (IQR, 75-88) years, and 148,018 (57.0%) were male.
The median no-flow time was 11 (IQR, 8-15) minutes.
Methods
Age-stratified dynamic probability curves were constructed to describe the time-dependent likelihood of favorable neurologic outcome according to no-flow duration.
Four age strata were used: 65 to 74 years, 75 to 84 years, 85 to 94 years, and 95 years or older.
The analytic approach identified the no-flow time at which the estimated probability fell below 1% with 95% CIs for each group.
This dynamic modeling approach allowed visualization of the continuous, time-dependent relationship between no-flow duration and outcome probability.
Discussion
The findings suggest the aging brain is increasingly vulnerable to ischemic injury during the no-flow interval, with very advanced age leaving almost no viable resuscitation window.
The authors note that 'the aging brain may be increasingly vulnerable to ischemic injury during this interval.'
The threshold for patients 95 years or older was 0 (95% CI, 0-0) minutes, suggesting that even minimal no-flow duration eliminates meaningful probability of favorable neurologic outcome.
The authors state these findings 'may inform resuscitation decision-making in aging populations.'
The burden of cardiogenic OHCA among older adults is described as increasing, making this age-stratified analysis clinically relevant.
What This Means
This research studied over 259,000 older adults in Japan who suffered cardiac arrest outside of a hospital between 2010 and 2023. The researchers focused on 'no-flow time' — the gap between when someone's heart stops and when emergency responders begin CPR — and how that window relates to the chance of surviving with good brain function. They found that overall, only about 3.4% of older cardiac arrest patients achieved a favorable neurological outcome at 30 days, and the tolerable no-flow window shrank dramatically with age.
Specifically, for adults aged 65–74, there was still roughly a 1% or greater chance of a good outcome if CPR was started within 14 minutes. For those aged 75–84, that window narrowed to 11 minutes. For adults aged 85–94, it dropped to just 2 minutes, and for those 95 and older, the threshold was effectively zero — meaning even a very brief delay before CPR was associated with essentially no chance of meaningful neurological recovery. These findings highlight that the aging brain appears to be especially sensitive to interruptions in blood flow during cardiac arrest.
This research suggests that age is a critical factor in understanding the potential benefit of resuscitation efforts after cardiac arrest, and that extremely short no-flow times may be necessary for the oldest patients to have any meaningful chance of recovery. These findings could potentially help emergency responders, patients, and families have more informed conversations about resuscitation decisions, particularly for very elderly individuals. The results do not tell individuals what decisions to make, but they provide population-level data about outcome probabilities that may be relevant to care planning.