Death after out-of-hospital cardiac arrest highest within first 3 years

The mortality rate following an incidence of out-of-hospital cardiac arrest (OHCA) is highest in the first 3 years post-event, gradually reducing over time, according to a study from Singapore.

“The available evidence suggests that standardized mortality ratio (SMR) among OHCA survivors is the highest in the early years post-OHCA and eventually normalizes to that of the general population,” the researchers said.

“Based on these findings, public health policy should pay close attention to OHCA survivors during the initial follow-up period, when they seem to be most vulnerable,” they said.

Using the Singapore data from the international Pan-Asian Resuscitation Outcomes Study (PAROS) and the Singapore Registry of Births and Deaths (2010–2019), the researchers identified 802 cases of OHCA (mean age of patients 56.0 years, 78.7 percent male, 68.8 percent Chinese). Individuals who died within 30 days of OHCA were excluded from the analysis.

About 61 percent of the cohort had received bystander CPR, 31 percent had hypothermia therapy initiated, and 72 percent had shockable first arrest rhythm. A majority of the patients (67.5 percent) were Cerebral Performance Category (CPC) grade 1–2.

The proportion surviving at 1, 5, and 10 years of follow up after OHCA* was 0.84, 0.68, and 0.62, respectively. The most common causes of death post-OHCA were pneumonia, chronic ischaemic heart disease, and acute myocardial infarction. [The Lancet Regional Health–Western Pacific 2022;doi:10.1016/j.lanwpc.2022.100672]

One year following OHCA, the SMR was 14.9 (95 percent confidence interval [CI], 12.5–17.8), which reduced to 1.2 (95 percent CI, 0.7–1.8) at 3 years and 0.4 (95 percent CI, 0.2–0.8) at 5 years.

Factors associated with an increased risk of mortality were CPC grade 3–4 (hazard ratio [HR], 4.62, 95 percent CI, 3.17–6.75) and age at OHCA event (HR, 1.03 [per 1-year increase], 95 percent CI, 1.02–1.04; p<0.001 for both). Conversely, shockable presenting rhythm was associated with a lower risk of mortality (HR, 0.70, 95 percent CI, 0.52–0.93; p=0.015).

The protective effect of shockable presenting rhythm was particularly evident among patients with CPC grade 1–2 compared with those with grade 3–4 (HRs, 0.36 vs 1.02).

Mean disability-adjusted life years (DALY) following OHCA reduced over the time period assessed, from 12.162 in 2010 to 3.599 in 2018. However, annual DALY post-OHCA fluctuated over time, ranging from 304.1 in 2010, rising to 849.7 in 2015, and then decreasing again to 547.1 in 2018.

“Our study is the first national Asian study to quantify long-term survival and disease burden of long-term OHCA survivors, to our knowledge, and thus represents an important contribution to current evidence,” remarked the researchers.

“[T]he overall decrease in the mean DALY from 2010 to 2018 in our study suggests that the long-term burden per OHCA patient has improved in Singapore over time,” they continued, highlighting improved interventions, including those in the community, as possible reasons for this.

Nonetheless, they cautioned against the assumption that OHCA was a “decreasing public health burden,” noting that the ageing population in Singapore may lead to an increase in total DALY in the future.

“Taken together with existing evidence, our study suggests that adult OHCA continues to exert a large burden of disease, warranting an increased focus on OHCA with regard to public health policy,” they said.

The researchers acknowledged that the lack of information on post-OHCA quality of life outcomes was a limitation. They also called for more research into identifying the reasons and mechanisms behind the variation in post-OHCA survival.