Objective: To evaluate the potential role of low serum Ca levels in the occurrence of sudden cardiac arrest (SCA) in the community. Patients and Methods: We compared 267 SCA cases [177 (66%) men] and 445 controls [314 (71%) men] from a large population-based study (catchment population ∼1 million individuals) in the US Northwest from February 1, 2002, through December 31, 2015. Patients were included if their age was 18 years or older with available creatinine clearance (CrCl) and serum electrolyte levels for analyses to enable adjustment for renal function. For cases, creatinine clearance and electrolyte levels were required to be measured within 90 days of the SCA event. Results: Cases of SCA had higher proportions of blacks [31 (12%) vs 14 (3%); P<.001], diabetes mellitus [122 (46%) vs 126 (28%); P<.001], and chronic kidney disease [102 (38%) vs 73 (16%); P<.001] than did controls. In multivariable logistic regression analysis, a 1-unit decrease in Ca levels was associated with a 1.6-fold increase in odds of SCA (odds ratio, 1.63; 95% CI, 1.06-2.51). Blood Ca levels lower than 8.95 mg/dL (to convert to mmol/L, multiply by 0.025) were associated with a 2.3-fold increase in odds of SCA as compared with levels higher than 9.55 mg/dL (odds ratio, 2.33; 95% CI, 1.17-4.61). Cases of SCA had significantly prolonged corrected QT intervals on the 12-lead electrocardiogram than did controls (465±37 ms vs 425±33 ms; P<.001). Conclusion: Lower serum Ca levels were independently associated with an increased risk of SCA in the community.
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