The long-held belief that sudden cardiac arrests (SCAs) occur most commonly on weekday mornings has been debunked by a team in Portland, Oregon, whose recent study of more than 1,500 SCA victims failed to identify any peak windows during which heart patients were prone to sudden cardiac death.
Results from the trial, an ongoing 15-year effort known as the Oregon Sudden Unexpected Death (SUDS) study, contradict a popular assumption that adults are more likely to experience sudden cardiac arrest on weekday mornings—especially Mondays. It’s a claim attributed to the psychosocial stressors of a new work week, and clinical evidence has backed that up.
“Earlier studies of SCA demonstrated a circadian and septadian pattern of incidence,” lead investigator Sumeet S. Chugh, MD, and co-authors wrote in Heart Rhythm, where the SUDS team published their latest results. “A morning peak, followed by a smaller peak in the afternoon, was initially reported in the Framingham cohort and subsequently verified in prospective community studies of SCA and in cohorts of patients implanted with an implantable cardioverter-defibrillator (ICD).”
For their work, Chugh, a professor of medicine and associate director of the Smidt Heart Institute at Cedars-Sinai Medical Center in Los Angeles, and his colleagues at Cedars-Sinai and Oregon Health and Science University focused on SCA patients in the metropolitan Portland area whose arrests were witnessed by at least one bystander or medical professional. Times of SCAs were determined based on the timing of 911 calls.
Between 2002 and 2014, the SUDS group identified 1,535 patients, majority male, who suffered a sudden cardiac arrest with a witness present. The majority of those SCAs took place in the afternoon (31.6 percent), and 27.6 percent and 26.9 percent occurred in the morning and evening, respectively. Chugh et al. didn’t observe any peaks in SCA prevalence, but they did see a nadir in early-morning events between 12 a.m. and 6 a.m. The drop was most drastic on Sundays.
According to the study, the pattern of early-morning nadir and lack of any peaks persisted when SCA cases were subanalyzed by age, sex and presence of coronary artery disease. The nadir wasn’t present only in cases where patients also suffered from sleep apnea.
Chugh and his team said the lack of a workday morning peak suggests something other than psychosocial stressors, which can further a patient’s risk of SCAs, ventricular arrhythmias, fibrosis and stenosis, might be at play.
“With the loss of the Monday peak, there seems to be some redistribution of these psychosocial stressors,” the authors wrote. "Although the exact mechanisms need further investigation, it is tempting to speculate a potential role of the advent of the Internet and smartphones, which allow for access to entertainment, social life and even work activities 24 hours a day, 7 days a week.”
They said their study’s “notable deviation” from the accepted norm indicates a need for more research.
“These findings have healthcare utilizations and public health implications, and warrant further investigation,” they wrote.
After graduating from Indiana University-Bloomington with a bachelor’s in journalism, Anicka joined TriMed’s Chicago team in 2017 covering cardiology. Close to her heart is long-form journalism, Pilot G-2 pens, dark chocolate and her dog Harper Lee.