Seasonality of mortality and in‐hospital complications in hip fracture surgery: Retrospective cohort research using a nationwide inpatient database

Abstract

Among older patients undergoing hip fracture surgery, previous studies have shown a seasonal variation of in-hospital surgical complications. However, little is known about seasonal effects on mortality and systemic complications after hip fracture surgery. In the present study, we evaluated whether mortality and in-hospital systemic complications are influenced by seasonal differences.Methods: We enrolled patients from a nationwide database who underwent hip fracture surgery between 2010 and 2018. The primary outcome was in-hospital mortality. The secondary outcomes were in-hospital systemic complications. The association between the seasonality and in-hospital outcomes was investigated using multivariable Cox, logistic regression and causal mediation analysis.Results: With 425 856 patients (mean age 83.5 years; 79% women), overall in-hospital mortality was 5324 (1.2%). Fall and winter were associated with a higher mortality than spring (hazard ratio [HR] 1.16; P < 0.001; HR 1.14; P = 0.001, respectively). Across all the seasons, there were 36 834 overall systemic complications (8.6%), with respiratory infection being the most frequent (18 637 [4.4%]). Among these complications, only respiratory infection showed seasonal variation, with a higher prevalence in fall and winter. The mediated effect of respiratory infection on mortality was significantly higher in fall and winter compared with spring (fall, HR 1.06, proportion mediated 36.7%; winter, HR 1.14, proportion mediated 55.0%; all P < 0.001). Conclusions:We found a significantly higher mortality in fall and winter after hip fracture surgery. Specifically, in winter, the increased in-hospital death was largely attributed to the increased incidence of respiratory infection.

Incidence of and risk factors for hip fracture in Nagasaki, Japan from 2005 to 2014

“…Several studies have demonstrated characteristic seasonality in hip fractures [ 10 , 15 – 17 ]. The present study clearly demonstrated an increase in the number of patients with hip fracture in winter, and a decrease in summer, consistent with the findings of Hagino et al [ 11 ].…”

“…The mortality rate of 0.43% in this study was extraordinarily low compared to previous epidemiological research. Stenqvist et al [ 24 ] and Ogawa et al [ 17 ] reported overall in-hospital mortality rates of 6.3% and 1.2%, respectively. Although detailed reasons for our result remain unclear, this inconsistency might be partially attributable to the relatively short observation period in our study, compared to the mean lengths of hospitalization of 24.9 days [ 24 ] and 35.96 days [ 17 ], respectively, in those previous investigations.…”

“…Stenqvist et al [ 24 ] and Ogawa et al [ 17 ] reported overall in-hospital mortality rates of 6.3% and 1.2%, respectively. Although detailed reasons for our result remain unclear, this inconsistency might be partially attributable to the relatively short observation period in our study, compared to the mean lengths of hospitalization of 24.9 days [ 24 ] and 35.96 days [ 17 ], respectively, in those previous investigations. In this study, mortality more than 8 days after ambulance transport or after transfer to other institutions was not able to be obtained and included.…”

Seasonality Affects Elderly Hip Fracture Mortality Risk During the COVID-19 Pandemic

“…and increased bone fragility in older patients due to seasonal variation in parathyroid hormone and vitamin D levels [1,11,12]. Various studies have also demonstrated a higher mortality rate associated with hip fractures in geriatric patients during the winter months [2,4,13,14].…”

“…Existing literature attributes some of the increased mortality to a worsening of pre-existing pulmonary and cardiovascular conditions and higher rates of pulmonary infections in geriatric patients during winter [13,15].…”