Increased Fall, Hip Fracture Risk Among Patients With AD Pathology

According to the results of a recent study, a large quantity of older hip fracture patients have cerebrospinal fluid evidence of Alzheimer disease (AD) pathology.

“Preoperative determination of AD biomarkers may play a crucial role in identifying persons without dementia who have underlying AD pathology in perioperative settings,” said lead study researcher Esther Oh, MD, PhD, associate professor of Medicine at the Johns Hopkins University School of Medicine and an associate director of the Johns Hopkins Memory and Alzheimer's Treatment Center, and colleagues.  

Historically, associations of AD pathology with gait disorder and falls among older adults without dementia have been reported. For their new study, the research team aimed to examine the prevalence and severity of AD pathology in older adults without dementia who fall and sustain hip fracture. They obtained cerebrospinal fluid from 168 hip fracture patients. Among these patients, 88.6% of the cognitively normal and 98.8% with mild cognitive impairment fell in the abnormal biomarker categories by the A/T/N classification.

In order to better understand why it is important to conduct a brief cognitive screening before surgery, along with other study findings, we spoke with Dr Oh.

Briefly highlight the object of your study. What was your patient population that you observed?

The goal of the study was to examine the prevalence of Alzheimer’s disease biomarkers in older adults who break their hips and underwent hip fracture repair surgery.

Can you explain how you used the cerebrospinal fluid of patients with hip fracture to determine Alzheimer Disease?

This study was part of a larger study published in JAMA Surgery (https://www.ncbi.nlm.nih.gov/pubmed/30090923) which examined the sedation level of anesthesia as an intervention to reduce the risk of delirium (acute confusion) after hip fracture repair surgery. In this study, one of the inclusion criteria was to be eligible for spinal anesthesia. We obtained cerebrospinal fluid during spinal anesthesia with the patient’s consent and examined for Alzheimer’s disease biomarkers. We designated cut off based on previously defined levels and determined what percentage of hip fracture patients had biomarkers that fell in the “abnormal” range.

How does cognitive impairment impact fall risk?

In an older adult, falls are usually due to multiple risk factors. Patients may have falls due to sensory impairment (vision, vestibular) as well as neuropathy, etc. Pertaining to this study, there has been accumulating evidence showing that AD pathology is associated with gait disorders, time to first fall, etc. This may be due to the pathology accumulating in brain regions that are important in motor function (walking, etc).

What should clinicians treating hip fracture look for in terms of identifying Alzheimer Disease?

We cannot diagnose dementia (including Alzheimer’s subtype) during an acute hospitalization (e.g. during hospitalization for an acute hip fracture). It should be done on an outpatient basis when the patients are more clinically stable. However, even a brief cognitive screening performed before surgery may reveal possible underlying cognitive impairment that was not noticed before. If the cognitive impairment persists even after recovering from the hip fracture, then the patient would most likely need an evaluation by their primary care physician.

What are the key takeaways from the study?

Because the underlying AD pathology can take many years to be clinically evident, it is possible to have pathology but not have obvious cognitive symptoms. However, in an acute situation such as hip fracture, hospitalization, etc., insults to the brain and the body may contribute to “unmasking” of the underlying disease. Clinicians should implement measures to minimize such insults in high risk population, such as a hip fracture population, even when they appear to be cognitively normal.

Reference:

Oh ES, Blennow K, Bigelow GE, et al. Abnormal CSF amyloid-β42 and tau levels in hip fracture patients without dementia [published online October 2018]. PLOS One.13(10): e0206719. https://doi.org/10.1371/journal.pone.0206719