By Harini Sarva, MD
Assistant Professor of Clinical Neurology, Weill Cornell Medical College; Assistant Attending Neurologist, New York Presbyterian Hospital
Dr. Sarva reports no financial relationships relevant to this field of study.
This population-based study using Medicare data demonstrated that in the five years prior to diagnosis of Parkinson’s disease (PD), when compared with age-matched controls, those who were diagnosed with PD had a higher incidence of traumatic brain injury (TBI). The TBI was rated as mild and concussive and was most often related to falls.
Camacho-Soto A, Warden MN, Searles Nielsen S, et al. Traumatic brain injury in the prodromal period of Parkinson’s disease: A large epidemiological study using Medicare data. Ann Neurol 2017;82:744-754.
The authors of this population-based study assessed Medicare data for patients aged 66 to 90 years from 2004 to 2009. Longitudinal data were gathered to determine the frequency of traumatic brain injury (TBI) in those with prodromal Parkinson’s disease (PD) (i.e., the period prior to diagnosis of PD vs. age-matched controls). Incident PD cases were those with the ICD-9 code 332.0. Atypical Parkinsonism was excluded based on individual ICD-9 codes. The ICD-9 code for TBI (V15.52) was used to determine the number of TBI cases in both groups during this period, and those incidents of TBI prior to this period were excluded. The primary endpoint was TBI up until PD diagnosis or control reference date. TBI was graded as mild or concussive and moderate/severe, and mechanisms of TBI included falls, motor vehicle accidents, and other mechanisms. PD patients (n = 89,790) were older than the control group, less likely to be smokers, more likely to be men, and had more comorbidities. In the five years preceding the first recorded PD diagnosis, there were 24,421 TBIs, with 18.6% occurring in those eventually diagnosed with PD and 6.52% occurring in controls. Of all the TBIs in both groups, 84% were characterized as mild/concussive. The most common cause of TBI in both groups (82% in those with PD and 74.4% in controls) was a fall followed by motor vehicle accidents. PD patients during the five-year prodromal period were at increased risk for TBI regardless of age and gender. Hazard ratios for TBI increased as time approached PD diagnosis, and the highest hazard ratios were in the year prior to diagnosis of PD.
COMMENTARY
Patients with PD have a higher risk of falls compared to age-matched controls. Having reliable predictors of falls can reduce morbidity and mortality in these patients. TBI as a prodromal PD marker may lead to more aggressive earlier treatment of PD with medical and physical therapies. Although the study was well powered and contained a considerable amount of demographic data, there are some important considerations. The time-frame of five years prior to the diagnosis of PD is not always reliable, as prodromal symptoms are not always accurately reported and none of the prodromal symptoms have a high enough sensitivity or specificity to individually predict PD. Also, we do not know if prodromal symptoms with higher sensitivities and specificities, such as rapid eye movement sleep behavior disorder, were ascertained during this five-year period to help determine if it is a true prodromal period. Next, as noted by the authors, some of these cases may be misdiagnosed as PD. They may have been atypical Parkinsonism, such as progressive supranuclear palsy, which in its early stages can appear quite similar to PD and is associated with early falls. Finally, PD is a clinical diagnosis based on motor features. If these features are subtle, those with PD may not have been diagnosed, thus misclassifying them as controls. Despite these limitations mainly derived from the use of ICD-9 data, the study demonstrates the importance of asking about early falls even in the most obvious cases, with the goal of reducing morbidity and mortality.
