Women are less likely to be resuscitated by bystanders than men in cases of out-of-hospital cardiac arrest (OHCA), and when resuscitation is attempted they see lower survival rates, according to research published in the European Heart Journal May 21.
Study head Marieke T. Blom, PhD, and colleagues based their work in the Netherlands, on a continent where the reported incidence of treated OHCA varies between 17 and 53 per 100,000 person-years. The authors said that while numerous studies have explored sex differences in OHCA, they’ve yielded conflicting results, with some suggesting men see better survival rates and others favoring women.
Blom, of the department of clinical and experimental cardiology at Amsterdam UMC, and her team said discrepancies in previous reports can likely be attributed to different inclusion criteria and population subsets. Rather than apply the same kinds of restrictions and risk the generalizability of their work, the researchers undertook a study of all emergency medical service (EMS)-treated resuscitation attempts in one Dutch province—5,717 cases in men and women between 2006 and 2012.
Twenty-eight percent of EMS-treated OHCAs were women, the authors reported, and they were less likely to be on the receiving end of a bystander intervention than men. While 67.9% of women received a resuscitation attempt from a bystander, that number was 72.7% in men, and it didn’t change much when a bystander physically witnessed the OCHA (69.2% in women and 73.9% in men).
Women also saw lower rates of survival than men, with 12% lower odds of surviving to hospital admission and 43% lower odds of surviving to hospital discharge than their male counterparts.
“Various explanations for inadequate recognition of OHCA in women may be proposed, for example lack of awareness that OHCA may strike women as often as men and the possibility that women themselves do not recognize the urgency of sentinel complaints,” Blom et al. wrote in EHJ. “We speculate that the latter may be due to biologic factors. For instance, during acute MI (a common trigger of OHCA), women may have more equivocal complaints such as fatigue, syncope, vomiting and neck/jaw pain, while men are more likely to report typical complaints such as chest pain.”
The authors said women’s drastically lower survival rates can be explained by a lower rate of shockable initial rhythm (SIR) in women (33.7% compared to 52.7% in men). OHCA with SIR can quickly dissolve into asystole if left untreated, and SIR is heavily influenced by OHCA location and the presence or absence of a witness.
Even after adjustment for patient and resuscitation characteristics, Blom and colleagues found lower proportions of SIR in women than in men, despite similar delays from an EMS call to recognition by the dispatcher. The researchers said the sex disparity is therefore probably the result of a longer delay from OHCA onset to recognition by bystanders or an EMS call, which makes sense since women are less likely to experience traditional symptoms of cardiac arrest and may self-identify the condition later than men.
Bystanders might also be less likely to recognize cardiac arrest in women, and we know from previous studies that witnesses sometimes avoid helping women because they’re nervous they’ll be accused of inappropriate touching or sexual assault.
Blom et al. said it’s also possible women see lower rates of survival from OHCA because most OHCAs occur at home, and because women tend to live longer than men, more widows might be living alone without immediate access to medical help.
“The suggestion from our findings that initial recognition of OHCA in women is lagging behind due to lack of awareness and demographic factors provides the incentive for education campaigns and reorganization of healthcare, for example development of systems for quicker access to resuscitation care for elderly women living alone or provision of more AEDs at residences of single elderly women,” the authors wrote. “To close the survival gap between sexes, further research is needed to resolve the (biological) causes for lower SIR rates in women, and to determine how OHCA in women can be recognized earlier, and how pre-hospital treatments must be modified.”