Seasonal variation in U.S. hospitalizations for chronic limb-threatening ischemia.

Background: Seasonal variation in coronary artery disease is well described, with a peak in the winter and a trough in the summer. However, little is known about seasonal trends in hospital admission for critical limb-threatening ischemia (CLTI) and associated outcomes.

Methods: Patients admitted with CLTI from January 1, 2012 through August 31, 2015 were identified in the Healthcare Cost and Utilization Project's National Inpatient Sample based upon administrative claims diagnosis codes. The primary outcome was seasonal hospitalization incidence, and secondary outcomes included mortality rates and rates of in-hospital major and minor amputations among nondiabetics and diabetics.

Results: Of 1,276,745 hospitalizations for CLTI during the study period, 28.3% occurred in the spring, the peak admission season, and 19.1% occurred in the fall, the nadir. In-hospital mortality was highest during the winter (adjusted odds ratio [OR]: 1.08; 95% confidence interval [CI]: 1.03-1.14), and followed the highest seasonal rates of influenza in the fall; however, other important comorbidities did not differ significantly by season. For the overall cohort, there was no significant seasonal variation in rates of major or minor amputation, although seasonal rates were different according to diabetic status. Patients without diabetes had the highest odds of amputation in the spring (OR 1.07; 95% CI: 1.02-1.12), although this trend was not identified among patients with diabetes.

Conclusions: There is significant seasonal variability in CLTI admissions and mortality but minimal variability in amputation rates. Understanding the seasonal variation in CLTI may help to identify individuals at greatest risk for hospitalization and death through patient and provider education efforts.