Clinicians treating patients with Parkinson disease (PD) and balance impairments are frequently faced with the difficult task of helping them overcome fall-related activity avoidance. Beyond the association with falls and impaired balance, fall-related activity avoidance has been identified as a risk factor for exacerbating impairments, thereby contributing to a greater functional decline and worsening disability in those with PD.1 Although several cross-sectional studies have identified an association between fear of falling and a variety of factors in PD, there is a need for prospective longitudinal studies to identify factors that predict fall-related activity avoidance.2,3 This would help clinicians provide more targeted interventions with the goal of preventing fall-related activity avoidance and its associated sequelae.

In this issue, Nilsson and colleagues4 begin to address this gap by examining predictive factors of fall-related activity avoidance in 151 people with PD over a 3-year period. A multivariate linear regression analysis was conducted with fall-related activity avoidance as the dependent variable and a number of baseline factors as potential predictors. The Modified Survey of Activities and Fear of Falling in the Elderly (mSAFFE), valid and reliable in PD,3 was used to measure the construct of fall-related activity avoidance. The mSAFFE is a 17-item self-administered questionnaire that asks participants to rate how often they avoid a wide variety of activities (eg, walking indoors, taking a shower, going to a doctor, or going out while it is slippery) on a scale of 1 "never avoid," 2 "sometimes avoid," and 3 "always avoid." Because there was multicollinearity between 2 of the predictor variables, concerns about falling (measured using the Falls Efficacy Scale-International [FES-I]) and perceived walking difficulty (measured using the self-administered Generic Walk 12 or [Walk-12G]), the authors developed 2 separate models to predict fall-related activity avoidance at 3 years, each containing only one of the 2 variables with significant covariance. In their first model, 4 factors explained 63% of the variability in mSAFFE scores at the 3-year follow-up. The strongest predictive factor was concerns about falling, followed by pain, unsteadiness while turning, and age. In the second model, perceived walking difficulties, followed by age, unsteadiness while turning, and pain, were found to be predictive of fall-related activity avoidance at 3 years, accounting for 50% of the variability.

Reflecting on the results of this regression analysis, it is apparent that many of these factors associated with the development of fall-related activity avoidance are modifiable risk factors commonly targeted by physical therapists. For example, physical therapists will commonly address gait difficulties and will work to reduce concerns about falling during an episode of care. However, identifying unsteadiness with turning as an independent predictor of fall-related activity avoidance may shift priorities. Furthermore, pain may not rise to the top of the list among the myriad of motor impairments (ie, poor postural control, weakness, bradykinesia, rigidity) that are generally considered to influence fall-related activity avoidance. We elaborate further on these less intuitive elements in the following text.

Unsteadiness while turning (as reported by participants when asked a "yes/no" question) was a predictor of fall-related activity avoidance in both models. Prior studies have revealed that the quality of turning is compromised in PD even during the early stages of the disease.5 Specific movement deficits can be categorized into perpendicular deficits (taking more steps and shorter steps and an altered turn strategy) and axial deficits (segment rigidity, altered segment coordination and timing, reduced segment rotation, and the effects of altered posture and postural control).6 It has been proposed that axial deficits may drive secondary responses in the perpendicular elements during turning in people with PD.6

An examination that undercovers the root cause of unsteady turning may be necessary to target the most impaired elements with the goal of reducing fall risk as well as fall-related activity avoidance. Where a multitude of patient goals and functional limitations compete for clinical time, this connection between difficulty turning and the future development of fall-related activity avoidance may assist clinicians in planning their sessions and developing targeted strategies and/or home exercise programs to optimize turning efficiency. One can anticipate a scenario where a patient mentions unsteadiness with turning as a minor complaint amongst a litany of other problems. Given this evidence, the therapist in this situation may want to ensure some components of the treatment plan address this problem more explicitly, knowing the future implications of unsteadiness with turning.

Both models also identify pain as a predictor of fall-related activity avoidance, which is a less intuitive finding. In this study, patients were screened for pain using a dichotomous question: "Are you bothered by pain?" With this open-ended question, not specifying a specific severity, location, or type of pain, this symptom was still found to be a significant predictor of fall-related activity avoidance at 3 years. Studies have shown that pain is experienced in 40% to 85% of individuals with PD.7 While pain is increasingly recognized as a nonmotor symptom of PD, pain remains undertreated in PD. Complicating the picture, pain in PD can be separated into multiple subtypes-some related directly to their PD and others to secondary factors. Multiple classification systems have been reported for subtyping pain in PD, commonly including subtypes such as central pain, neuropathic pain, dystonia, akathisia (or, a subjective sense of restlessness), and musculoskeletal pain.8,9 The distinction between these types of pain can have important implications for what types of treatment may work best and may suggest directions for future improvements in pain management in PD. For example, a recent study on a large cohort of individuals with PD found that nearly one-third of the participants had signs of central neuropathic pain (eg, allodynia), although only 3% of their cohort reported receiving relief from medication targeting central pain mechanisms such as gabapentin, pregabalin, or amitriptyline,10 suggesting that central pain mechanisms may be undertreated in this population.

Physical therapists are in a unique position to screen for these different patterns of pain and to address them accordingly. For example, a physical therapy program to address pain that is primarily neuropathic in nature will vary significantly from a treatment plan for a patient with a more localized, musculoskeletal problem.11 This approach would address the source of pain while promoting an increase in activity level, thereby preventing fall-related activity avoidance. These results may encourage therapists to consider pain as a potential modifiable source of fall-related activity avoidance.

The findings of this study identify predictive factors of fall-related activity avoidance that may be underaddressed among the numerous, complex impairments and activity limitations characteristic of PD. A treatment approach that targets unsteadiness with turning and pain has the potential to reduce fall-related activity avoidance, thereby limiting the onset of secondary sequelae associated with inactivity among persons with PD.

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