Sudden cardiac death during nighttime hours

Background: In the absence of apparent triggers, sudden cardiac death (SCD) during nighttime hours is a perplexing and devastating phenomenon. There are few published reports in the general population, with insufficient numbers to perform sex-specific analyses. Smaller studies of rare nocturnal SCD syndromes suggest a male predominance and implicate sleep-disordered breathing. Objective: The purpose of this study was to identify mechanisms of nighttime SCD in the general population. Methods: From the population-based Oregon Sudden Unexpected Death Study, we evaluated SCD cases that occurred in the community between 10 PM and 6 AM (nighttime) and compared them with daytime cases. Univariate comparisons were evaluated using Pearson χ² tests and independent samples t tests. Logistic regression was used to further assess independent SCD risk. Results: A total of 4126 SCD cases (66.2% male, 33.8% female) met criteria for analysis and 22.3% (n = 918) occurred during nighttime hours. Women were more likely to present with nighttime SCD than men (25.4% vs 20.6%; P < .001). In a multivariate regression model, female sex (odds ratio [OR] 1.3 [confidence interval (CI) 1.1–1.5]; P = .001), medications associated with somnolence/respiratory depression (OR 1.2 [CI 1.1–1.4]; P = .008) and chronic obstructive pulmonary disease/asthma (OR 1.4 [CI 1.1–1.6]; P < .001) were independently associated with nighttime SCD. Women were taking more central nervous system–affecting medications than men (1.9 ± 1.7 vs 1.4 ± 1.4; P = .001). Conclusion: In the general population, women were more likely than men to suffer SCD during nighttime hours and female sex was an independent predictor of nighttime events. Respiratory suppression is a concern, and caution is advisable when prescribing central nervous system–affecting medications to patients at an increased risk of SCD, especially women.