Delirium is one of the most common complications for elderly patients with proximal femoral fractures^1,2,3). The incidence rate of delirium after a proximal femoral fracture varies drastically by race (from 4–61%)²⁾. Delirium, which is a neurobehavioral syndrome in which normal neural activity is altered, can be caused by a variety of mechanisms⁴⁾. Delirium is associated with longer hospital stays, worse prognoses, and increases in healthcare expenses and mortality rates in senile patients with proximal femoral fractures^1,5). Known risk factors of delirium are being 65 years of age or older, male sex and dementia or depression⁶⁾, however other risk factors may also exist (e.g., transfusion, type of fracture, type of operation, American Society of Anesthesiologists [ASA] classification, body mass index [BMI], time until operation after fracture, preoperative albumin levels, preoperative hemoglobin levels). It is also possible that a post-fracture sleep disorder may be the cause of delirium, with secondary symptoms developed as a result of the delirium⁷⁾, however, studies to date have been insiufficient to confirm this possibility. Here, the potential relationship between sleeping disorders and delirium in patients with surgically treated proximal femoral fractures was investigated. The hypothesis tested here was that a sleeping disorder occurring after surgical treatment of a proximal femoral fracture could be a risk factor for the development of delirium. Thus, the objective of this study was to characterize the relationship between sleep disorders and the development of delirium in patients with surgically treated proximal femoral fractures.

Among the 283 patients included in the final analysis (i.e., after removal of 33 for exclusion criteria described above), 170 had intertrochanteric fractures and 113 had femoral neck fractures. Reconstructive surgery was used in 115 patients (total hip arthroplasty [n=12] and hemiarthroplasty [n=103]), and 168 underwent internal fixation for osteosynthesis. There were 28 patients (9.9%) with a history of dementia (Table 2). After the fracture, more than one third of patients (n=101; 35.7%) were diagnosed with sleeping disorders and 48 (17.0%) demonstrated delirium (Table 3). The sensitivity and specificity of a sleeping disorder to predict the development of delirium were 0.75 and 0.76, respectively; the positive and negative predictive values were 0.64 and 0.93, respectively. The mean time to operation after fracture was 5.77±3.58 days; neurology consultation for the management of delirium occurred at a mean of 7.25±3.22 days after fracture. Among the predicted risk factors for delirium, only sleeping disorder and history of dementia were significantly related to the development of delirium (P<0.05). Odds ratios were 7.85 for sleeping disorder and 7.76 for history of dementia. The remaining predicted risk factors tested were not significantly related to the development of delirium. The adjusted odds ratio with sex, age, and BMI is 5.78 for those with a sleeping disorder and the development of dementia, a relationship that is statistically significant (P<0.01). Those who had a history of dementia, the adjusted odds ratio with sex, age, and BMI for the development of delirium is 6.03, also statistically significant (P<0.01) (Table 4).

The reported prevalence rates for delirium after a proximal femur fracture varies greatly depending on the study (4–61%)²⁾; this wide range can be explained, at least in part, by the definition of delirium used11). In this retrospective study, delirium was diagnosed by a neurologist after an assessment of potential cognitive impairment. The observed incidence rate of delirium in this study is 17%, a value similar to a study by Inouye et al.¹²⁾, but one which could also be underestimated if a neurology consultation was not obtained. Kim and Kim¹³⁾ classified delirium into those resulting from either predisposing causes or trigger causes; predisposing causes include dementia or cognitive disorder, decreased performance ability, visual field defect, history of alcohol abuse and age older than 70 and trigger causes include dehydration, hypoxia, ischemia, infection and fracture, sleeping disorder, and environmental factors (e.g., intensiive care unit [ICU] care)¹⁴⁾. In addition, Altman et al.⁷⁾ reported that higher ASA scores prior to operation and preoperational delirium are potential causes of postoperational delirium. Fong et al.⁴⁾ stated that impaired hearing and vision, insertion of catheter, activity restriction with restraints, medication, acute neuropathy (e.g., cerebral infarction, encephalitis), infection, anemia, disease, such as dehydration, operation, ICU care, sleeping disorder and pain are modifiable factors. In contrast, there are factors that could not be modified such as dementia, old age, history of delirium before, cerebral infarction, male, chronic neuropathy, and chronic liver disease. As seen from previous studies, a sleeping disorder is a predisposing factor or risk factor that can be modified to prevent delirium. However, to date, there has been insufficient research on the concomitant incidence of delirium and a sleeping disorder. Here, it was observed that if a patient has history of dementia, they are 6.03 times more likely to have delirium after a proximal femoral fracture. Patients with sleeping disorders after proximal femoral fracture have an adjusted odds ratio of 5.78 of experiencing delirium compared with those who does not.

This study has several limitations. First, it is a retrospective study using electronic medical records charts, thus the dates of delirium and sleeping disorder occurrence may be inaccurate due to negligence of recording. Second, since this study covers the elderly, sub-acute delirium may be misdiagnosed as a deconditioning postoperative event. Third, delirium could be underestimated when symptoms involved hypoactive conditions. However, rounds were made every day, and efforts were made to check patient conditions daily. Fourth, there were several inefficiencies when defining a sleeping disorder– polysomnography, electrocephalogram, and blood testing were not used to identify the cause. A self-reported questionnaire (PSQI) was used to assess sleep quality. Fifth, sleeping problems can be due to a chronic illness described on Charlson's comorbidity index, such as diabetes, arthritis, human immunodeficiency virus/acquired immunodeficiency syndrome, lupus, Parkinson's disease, Alzheimer's disease, and multiple sclerosis. There were a few comparable cases with the Charlson's comorbidity score. This system has greater advantages for the prediction of mortality, but relatively less well characterized for older patients because lots of index diseases are unnecessary. The ASA score system was also used for chronic illness as variants. Further prospective studies may be needed to overcome such limitations.

Our study suggests that in proximal femur fracture patients aged 60 or older, sleeping disorders which occur after surgery are significantly related to and an independent predictive factor for the development of delirium.

Flow chart of patients with proximal male/female fracture.