Clinical Characters And Relevant Research Between Gait And Cognitive Function In PD Patients

Background: Gait disorder is one of the most common movement symptoms in Parkinson’s disease(PD). As the disease progresses, the incidence and severity of gait disorders gradually increase. Within 3 years after first diagnosis, more than 85% of PD patients face clinical gait dysfunction. Patients with Parkinson’s disease(PD) may result in a series of potential problems, such as increased risks of disability and falls, decreased quality of life. In long term studies, as disease course increases, 40%-90% PD patients will fall off, e.g., 45%-50% PD patients will fall off during walking. In our daily life, we often experience the situation of walking while performing an additional movement or cognitive tasks, such as walking while talking to family members, or with a cup of coffee in hand. PD patients will show aggravated gait disorder during dual-task. In recent years, people pay more attentions on dual-task walking test, with study subjects including normal old people, dementia patients, young people and patients with some neurological diseases. However, studies are rare on PD patients, especially in advanced PD patients. Turning around is a very important daily activity for PD patients to face with, but there is rare report about the turning movement characteristics when PD patients perform another task. Thus, it is worth further investigating the similarities and differences between turning and walking while performing another task. Furthermore, advanced PD patients often have more severe gait disorders and significant difference in movement disorders during "medication-on” and “medication-off” state. With the progress of the disease, fluctuations in symptoms, reduced efficacy of dopamine, and medication wearing-off effect are inevitable, which is similar to off-state. Therefore, this is the state that each of the advanced PD patients has to face. In this state, PD patients are most likely to fall. It is particularly important to understand the relationship between cognitive task and motor task during " medication-on” and “medication-off” state, and study how cognitive resources are assigned to these two tasks. Though studies on dual-task are increasing in recent years, relevant mechanism and studies are relatively less. Discussion and understanding on current mechanism are not sufficient, and further studies are still necessary.Clinical symptoms of PD include motor and nonmotor symptom, cognitive impairment is a very common nonmotor symptom of PD patients. Mild cognitive impairment(MCI) is a transition from normal people to dementia. In patients with Parkinson’s disease but no dementia, or even in PD patients with drugs not administered, mild cognitive dysfunction is very common, and this transition phase is named as PD with mild cognitive impairment(PD-MCI). In a 20 year follow-up study on patients with PD newly diagnosed, it is indicated that the final occurrence of dementia is 80% in PD patients. PD dementia(PDD) has multiple effects on quality of life and disease progress. It can decrease quality of life, increase home nursing expense, and result in increased death rate. PD-MCI is the high risk factor for PD to develop into dementia, so it is very important to early diagnosis. In previous studies, different criteria have been adopted to diagnose PD accompanied with mild cognitive impairment, so these studies have inconsistent criteria. However, there is no related domestic study on relationship between cognitive function and postural instability/gait disorder. The study adopted the diagnostic criteria recommended by Movement Disorder Society(MDS) Task Force, utilized the recommended assessment scale- Montreal Cognitive Assessment, to investigate the characteristics of cognitive impairment, thus to provide helps for performing effective intervention.Objective: To study the effects of dual-task on cognitive and motor functions in patients with advanced Parkinson’s disease(PD), and explore the relationship between cognitive function and gait. Furthermore, to investigate the related factors, clinical characteristics of PD-MCI and its predictors.Methods: From Nov. 2013 to Feb. 2015, 20 idiopathic PD patients and 20 normal adults(family numbers of PD patients) were recruited from department of neurosurgery in Tangdu hospital of Fourth Military Medical University. Cognitive functions were evaluated by Mo CA(Beijing version), executive function by similarity test, digit span test and digit symbol test in Wechsler adult intelligence scale(modified China version). Motor functions were evaluated by combining video analysis, to compare performance of dual-task between normal adult group and PD group, when "medication-on" and "medication-off" state(controlling factors of different groups included age, gender, total cognitive function score and executive function score).A total of 81 patients were enrolled from department of neurosurgery in Tangdu hospital of Fourth Military Medical University, 11 potential PDD patients were excluded, and the remaining 70 PD patients satisfied inclusion criteria. By referring to PD-MCI diagnostic criteria of MDS Task Force, Mo CA and Unified Parkinson’s Disease Rating Scale(I-III) were adopted to evaluate PD patients.Results: During "medication-on" and "medication-off" state in PD group, under dual-task+3(DT+3) and dual-task-7(DT-7) conditions, step velocity, step length, rotation velocity, and cognitive task(DT+3 and DT-7) were reduced compared to single task condition(P<0.05). Under DT-7 condition, step velocity, step length, rotation velocity, and cognitive task were further reduced(P<0.05).During "medication-on" and "medication-off" state, under dual-task conditions(DT+3, DT-7), step velocity, step length, rotation velocity were affected to similar degrees(P>0.05), but cognitive task(DT+3 and DT-7) was more significantly reduced during "medication-off" compared to "medication-on"(P<0.05).During "medication-on" state, step velocity, step length and rotation velocity showed significantly different DTC under DT-7 condition(P<0.05), but not under DT+3 condition. During "medication-off" state, under DT+3 and DT-7 conditions, significantly different DTCs were observed in step velocity and rotation velocity(P<0.05) rather than step length and rotation velocity(P>0.05).Under DT+3 and DT-7 conditions in normal people group, step velocity and step length were reduced compared to single task condition(P<0.05). The performance of rotation velocity and cognitive task declined markedly under DT-7 condition compared to single task condition(P<0.05). Under DT-7 condition, step velocity, rotation velocity, and cognitive task were further declined than under DT+3 condition(P<0.05), but step length showed no statistical difference(P>0.05).Under dual-task conditions(DT+3 and DT-7), compared to normal adult group, the step velocity and step length were significantly reduced in PD group, during "medication-on" state(P<0.05), while there was no significant change for rotation velocity(P>0.05). Under DT-7 condition, motor tasks had significant influences on cognitive tasks(P<0.05).Of 81 PD patients, 47 patients were PD-MCI(58%), 23 patients had no cognitive impairment(28%). PD-MCI and PD with no cognitive impairment(PD-NCI) had significant differences in education degree, H&Y staging and levodopa equivalent daily dose(LEDD)(P<0.05); The score in PD-MCI group was significantly lower in visuospatial/executive function, delayed recall, attention, language, abstract subdomains compared with that of PD-NCI group(P<0.05); UPDRSⅢ and postural instability and gait disorder(PIGD) were significant difference in two groups(P<0.05).Mo CA scores were negatively correlated with age(r=-0.31, P<0.05), H&Y stages(r=-0.44, P<0.05), UPDRS- Ⅲscore(r=-0.32, P<0.05), UPDRS- Ⅱ(r=-0.35, P<0.05), UPDRS- Ⅰ(r=-0.40, P<0.05), bradykinesia(r=-0.38, P<0.05) and PIGD(r=-0.31, P<0.05), and positively correlated with education(r=0.30, P<0.05). Including Mo CA score as the dependent variable, and age, H&Y stage, education, UPDRS-Ⅲ, UPDRS-Ⅱ, UPDRS-Ⅰas the independent variables, PD-MCI was predicted by age(β coefficients-0.06, P<0.05) and H&Y stage(β coefficients-0.80, P<0.05). Bradykinesia and PIGD scores were singly included as independent variables to observe independent influences of subscore of UPDRSIII on cognitive functions, and the results showed that bradykinesia was the predictor of PD-MCI(β coefficients-0.12, P<0.05).Conclusion: Dual-task test has negative influences on gait and cognitive functions of advanced PD patients(including "medication-on" and "medication-off" state) and adults with normal cognitive functions. The more complex the cognitive tasks become, the greater impairment in gait adjustment occurs.The influences are especially obvious on PD patients. Under dual-task conditions in PD patients during "medication-on" and "medication-off" state, distribution of cognitive resources decision may have differences during motor task and cognitive task. Patients during "medication-off" state may need to occupy additional cognitive resources to compensate poorer motor and balance disorder to avoid falling off. Turning around is affected more significantly by cognitive task than walking straightly, the reason for which may be that turning around occupy more cognitive resources. The "dual-task phenomenon" demonstrated in PD patients is not a special phenomenon due to the disease, but may be closely correlated with three basic factors including total cognitive resources, motor task and cognitive task.Mild cognition impairment is one of the common nonmotor symptoms with highly prevalence in PD, which is mainly characterized by the dramatic impairments in the cognitive domains of visuospatial and executive function, delayed recall, attention, language. Poorer cognitive performance is associated with increasing disease severity, age, movement disorder and education, especially in bradykinesia and PIGD. Mild cognitive impairment may be predicted by age, H&Y and bradykinesia.