Seasonal pattern in elderly hospitalized with acute kidney injury: a retrospective nationwide study in Italy

Abstract

Purpose Acute kidney injury (AKI) frequently complicates hospitalization and is associated with in-hospital mortality (IHM). It has been reported a seasonal trend in different clinical conditions. The aim of this study was to evaluate the possible relationship between seasons of the year and IHM in elderly hospitalized patients with AKI. Methods We selected all admissions complicated by AKI between 2000 and 2015 recorded in the Italian National Hospital Database. ICD-9-CM code 584.xx identified subjects with age ≥ 65 years and age, sex, comorbidity burden, need of dialysis treatment and IHM were compared in hospitalizations recorded during the four seasons. Moreover, we plotted the AKI observed/expected ratio and percentage of mortality during the study period. Results We evaluated 759,720 AKI hospitalizations (mean age 80.5 ± 7.8 years, 52.2% males). Patients hospitalized with AKI during winter months had higher age, prevalence of dialysis-dependent AKI, and number of deceased patients. In whole population IHM was higher in winter and lower in summer, while the AKI observed/expected ratio demonstrated two peaks, one in summer and one in winter. Logistic regression analysis demonstrated that parameters such as age, autumn, winter, comorbidity burden were positively associated with IHM. Conclusion We conclude that a seasonality exists in AKI, however, relationship between seasons and AKI could vary depending on the aspects considered. Both autumn and winter months are independent risk factors for IHM in patients with AKI regardless of age, sex and comorbidity burden. On the contrary, summer time reduces the risk of death during hospitalizations with AKI.

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“…Studies on multiple unrelated conditions have demonstrated a similar pattern, with barely noticeable seasonal variability in amputation rates for critical limb‐threatening ischemia, but hospitalization patterns aligning with influenza waves 34 . An elevated incidence of hospitalization for acute kidney injury was observed in winter, and during this period, the mortality rate among those hospitalized was found to be highest 35 . An increased winter mortality rate was observed in intensive care units, which remained statistically significant even after adjusting for diagnosis 36 .…”

“… 34 An elevated incidence of hospitalization for acute kidney injury was observed in winter, and during this period, the mortality rate among those hospitalized was found to be highest. 35 An increased winter mortality rate was observed in intensive care units, which remained statistically significant even after adjusting for diagnosis. 36 Common pattern emerges among these studies—little increase in typical symptoms, some increase in hospitalization, and significant increase in mortality.…”

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“…It is well known that a wide number of diseases do not occur randomly through the year, but exhibit preferred monthly or seasonal variations. For example, acute kidney injury in elderly patients, the occurrence of delirium in patients admitted to medical units, and many cardiovascular disorders, such as aortic disease, pulmonary embolism, venous thromboembolism, myocardial infarctions, transient ischemic attacks, heart failure and acute cardiovascular diseases [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. Flare-ups of multiple sclerosis and peptic ulcer hospitalizations also show a seasonal pattern [ 34 , 35 ].…”