The “July effect” on patients admitted with diabetes ketoacidosis: a national retrospective cohort study

Abstract

Background Every July, new residents begin training across the United States, but it is unclear whether this affects the mortality rate of critically ill patients such as those with diabetes ketoacidosis (DKA). Methods This national retrospective cohort study included patients aged 18 years or older admitted to acute care with DKA between 2016 and 2020. Data were obtained from the National Inpatient Sample Database. We compared patients admitted in July and August with those admitted during the remaining months and assessed the primary endpoint of all-cause inpatient mortality. We also obtained an odds ratio adjusted for confounders using multivariate logistic regression analysis. Secondary endpoints included length of hospital stay, total hospital charges, the crude rate of mechanical ventilation, acute kidney injury requiring hemodialysis, and vasopressor requirement. Hypothesis testing was conducted using the chi-square test for categorical variables and Student’s t test for continuous variables. A two-tailed P value of < 0.05 was considered statistically significant. Results Of the 269,095 hospitalizations identified over 5 years with a discharge diagnosis of DKA, 250,990 met the inclusion criteria. During July and August, 42,668 (17%) hospitalizations occurred, and 208,322 (83%) occurred during the remaining months. The mean age of the patients was 47 years, and there was no significant difference among the cohorts (P = 0.41). Female patients represented 54% of the total patients, and there was no difference between the cohorts (P = 0.68). Of the admitted patients, 61% were White, 21% were Black, and 11% were Hispanic, with no differences between the cohorts (P = 0.38). Medicare (35%) and Medicaid (30%) were the primary payers for most patients, and approximately 25% had private insurance. There were no differences between the cohorts in terms of primary payers (P = 0.49). The mean length of stay was 7 days, and the total hospitalization cost was $85,509. Admission in July or August did not increase the odds of inpatient mortality (adjusted odds ratio 0.96, P = 0.58). Conclusions In this retrospective cohort study of patients admitted with DKA, inpatient care during July and August did not increase the odds of inpatient mortality.