Increased 30 day mortality after weekend admission for acute myocardial infarction: results from the Norwegian Myocardial Infarction Registry

Background/Introduction Hospitals operate with reduced staffing levels during weekends. Weekend admissions for acute myocardial infarction (MI) are fewer than weekday admissions, and the proportion of NSTEMI is lower. Prior studies have suggested increased mortality among patients admitted during weekends; however, the degree to which this reflects differences in case mix remains uncertain. Purpose To evaluate whether 30-day mortality is higher among patients admitted during weekends compared with weekdays, adjusting for MI type (STEMI/NSTEMI) and relevant clinical risk factors. Methods All Norwegian hospitals are mandated to report hospitalized cases of acute MI (ICD-10 I21–I22) to the Norwegian Myocardial Infarction Registry (NORMI). The registry includes detailed information on medical history, clinical presentation, diagnostic assessments, treatments, and discharge medications. Logistic regression models were used to estimate 30-day mortality associated with weekend versus weekday admission. Models were adjusted for age, sex, MI type (STEMI/NSTEMI), and the risk factors prior MI, diabetes and hypertension. Results From 2018 to 2024, 77 004 acute MI hospitalizations were recorded. The overall unadjusted 30-day mortality was 8.5%. In the age- and sex-adjusted model, weekend admission was associated with higher mortality (OR 1.10, p < 0.01). Adjustment for MI type reduced the estimate (OR 1.08, p = 0.01), and further adjustment for risk factors produced an identical result (OR 1.08, p = 0.01). Mondays had, on average, a 12% higher number of admissions compared with Tuesday–Friday. In the full model excluding Monday admissions, the OR was 1.07 (p = 0.03). In the full model, only including STEMI, the OR was 1.12 (p=0.03). Conclusions Weekend admission for acute MI is associated with higher 30-day mortality compared with weekday admission. This association persists after adjustment for MI type and key clinical risk factors. Further analyses examining the association with time to treatment are warranted.