Parkinson disease (PD) is the second most common progressive, irreversible neurodegenerative disorder in the United States.1 A debilitating disease that interferes with the physical, mental, emotional, and social aspects of an individual's being, PD eventually leads to difficulty with activities of daily living (ADLs) and decline in quality of life (QOL). Treatment options for PD are limited to pharmacologic management and surgery. These therapies have been designed to ameliorate symptoms, namely motor dysfunction, and to slow their progression. To date, researchers have been unable to develop treatments aimed at reversing the disease. However, less invasive alternatives, such as exercise, have captured the attention of scientists and clinicians as possible adjunctive therapy. Research thus far has primarily focused on the role of exercise in improving motor, cognitive, and emotional complications of PD. This article reviews recent literature demonstrating the benefits of exercise in patients with early PD and its impact on QOL.
According to the Parkinson's Disease Foundation, 7 million to 10 million people worldwide suffer from PD; 1 million of them live in the United States. Recent statistics show that PD is diagnosed in about 60,000 Americans each year. Approximately five in every 100,000 individuals younger than 40 years have PD; in persons older than 70 years, however, the incidence increases to 700 in every 100,000 population. Men are 1.5 times more likely to be affected than women.2,3
The total costs associated with PD are estimated to be $25 billion per year in the United States. These expenses include the cost of health care visits and treatments and the amount of lost income resulting from inability to work. Medication alone costs each patient approximately $2,500 per year; those who require surgical intervention pay an additional $100,000.3
The pathogenesis of idiopathic PD is characterized by the degeneration of dopaminergic neurons in the basal ganglia, specifically within the substantia nigro-striatum pathway. In a healthy brain, dopamine serves as an inhibitory neurotransmitter that helps regulate the body's motor activity by sending signals to such areas as the cerebral cortex. Essentially, dopamine provides a sort of “checks and balances” system in conjunction with excitatory neurotransmitters, namely acetylcholine. In a person with PD, however, the brain is unable to maintain this equilibrium because of the decrease in dopamine levels. As a result, acetylcholinedependent neuronal circuits continue to stimulate the cortex uninhibited, thereby leading to motor dysfunction.2,4
The clinical findings of PD encompass changes in motor function, cognition, and emotion. Abnormal motor functioning is the dominant feature of this disorder. Most patients present with a combination of resting pin-rolling tremor, cogwheel rigidity, and bradykinesia isolated to one extremity or extremities on one side of the body. As the disease progresses, these symptoms become more generalized and debilitating. Stooped posture, festinating gait, masked facies, dysphasia, and autonomic nervous system compromise may occur in later stages of PD.2,4 Secondary features include decreases in muscle strength and balance/coordination.
In addition to its role in controlling voluntary movements, dopamine is also an important component of cognition and emotion. Approximately 10% to 15% of patients with PD develop some degree of dementia.4 Alterations in emotion, namely depression, have been estimated to affect 40% to 50% of individuals with PD.1 Patients who experience changes in cognition and psychological status may suffer a greater decline in QOL than those who have abnormal motor symptoms alone.
STAGING PARKINSON DISEASE
Two main classification systems are used to clinically stage PD. Each approach categorizes patients by the presence and degree of motor, cognitive, and/or psychological symptoms. The Hoehn and Yahr method primarily evaluates individuals according to the severity of their motor symptoms and associated functional impairment. Depending on the findings, the patient's disease is then placed in one of the following five categories: stage I-II signifies minimal/mild disease; stage III, moderate disease; and stage IV-V, severe disease or invalidism status5 (Table 1).
The second systematic approach is known as the Unified Parkinson's Disease Rating Scale (UPDRS). This technique assesses patients based on a 55-item evaluation of nonmotor experiences of daily living, motor experiences of daily living, motor examination, and motor complications (Table 2). Forty-eight of the UPDRS items are rated on a scale of 0 to 4 (0 = normal, 1 = mild, 2 = moderate, 3 = severe, 4 = marked) corresponding to the severity of specific nonmotor and motor symptoms. The remaining seven components focus on yes/ no questions that indicate the presence or absence (numeric value, 1 and 0, respectively) of additional pertinent clinical findings. These scores are then totaled to give a value between 0 and 199, which in turn provides patients with an overall level of disability. Clinically, a UPDRS score of 0 represents no apparent disability, while UPDRS values of 1-50 suggest mild cases; 51-100, moderate disease; 101-150, severe functional impairment; and 151-199, complete disability.6
POSITIVE EFFECTS OF EXERCISE
Exercise has a significant impact on maintaining a balanced lifestyle. In a generally healthy individual, exercise enhances mood, cognitive function, and sleep by increasing the release of neurotransmitters, such as dopamine and serotonin. Exercise can improve gross and fine motor coordination as well as strength. In addition, physical activity boosts the body's metabolism, leading to an increased energy level, improved weight control, and prevention and/or modification of disease.
- Gait training, resistance, balance/coordination, activities of daily living, and tandem cycling improve motor abnormalities in Parkinson disease (PD).
- Self-assessment of patients with PD following exercise regimens shows improvement in cognitive functioning and reduced depression.
- Positive effects of exercise on symptoms of PD result in a better quality of life.
- While further research is needed to address long-term effects and influence on later stages of PD, clinicians should consider implementing exercise in conjunction with pharmacologic therapy.
The studies selected for this review differed in their approaches to examining the effects of exercise in PD patients but used similar patient selection and management protocols. Criteria for participating in these studies included a diagnosis of idiopathic PD, age greater than 40 years, a Hoehn and Yahr score of I-III or UPDRS value less than 50, and a Mini-Mental State Examination (MMSE) score higher than 20. Patients were excluded if they suffered from neurologic, cardiovascular, or musculoskeletal disorders that could have prevented them from continuing to completion or carried risks for complications. Participants' daily PD medication regimens were maintained throughout the course of the studies. Training and assessment of variables, both at baseline and on completion of the research, were conducted at least 1 hour following pharmacologic treatment. On average, patients participated in training programs for 1 to 6 months, exercising 30 to 90 minutes two to seven times a week. Researchers studying the influence of exercise on motor, cognitive, and emotional symptoms of PD have developed a variety of workout programs (Table 3).
Motor dysfunction and exercise Motor dysfunction is the chief clinical finding in patients suffering from PD. Studies examining the effects of exercise in these patients have found promising evidence of improvements in motor deficits. Compared with controls, participants completing training programs experienced a decrease in UPDRS scores as indicated by improvement in ADLs, bradykinesia, rigidity (41% reduction), and tremors (38% reduction).7–9 Significant improvements in mobility following exercise have also been established through assessment of lower-extremity tasks, including a 10- to 20-meter walking test, timed up and go (TUG) test, time required to go up and down a flight of stairs or arise from an armless chair without using the hands, and maximum walking distance. The 10- to 20-meter walking test assesses mobility by determining the speed at which the patient walks a distance of 10 or 20 meters from a stationary standing position. The TUG task measures the time needed for participants to walk three meters from a seated position, turn around, and return to sitting. When analyzed against control groups, the speed and times recorded in the 10- to 20-meter walking and TUG tests were significantly faster for those partaking in exercise.7,8,10,11 In addition, physical activity significantly correlates with a decrease in time needed to go up and down a flight of stairs or arise from an armless chair without using the hands and an increase in total walking distance.12,13
Muscle strength has also been shown to improve with exercise. Researchers found improvement in strength of affected lower and upper extremities after resistance training by measuring force or maximum weight lifted compared to controls.10,14 Interestingly, a study conducted by Ridgel and colleagues found that tandem stationary cycling at a rate of 80 to 90 rpm (forced exercise) globally increased muscle strength compared to baseline and performance of patients who independently cycled at their preferred rate (voluntary exercise).9 Evaluation of grip force applied against increasing load showed a positive trend in the forced exercise group.
Finally, balance and coordination, ie, dexterity, have been of interest in the literature evaluating the effects of exercise on PD. Regarding dexterity of the lower limbs, Gobbi and colleagues observed improvement in balance using Berg's Functional Balance Scale (FBS) at the end of training. FBS consists of 14 tasks, such as sitting down-standing up from a chair and standing on one leg. Each task is assigned a particular number of points based either on the time taken to complete the activity or quality of performance. Scores are totaled, with a maximum of 56 points; a higher score indicates better balance. Likewise, researchers led by Fisher demonstrated a 33.3% increase in symmetry among the high-intensity training group during a sit-to-stand test, suggesting more equally distributed body weight and balance. In the study conducted by Hirsch and colleagues, use of the computerized program Equi Test revealed that patients who exercised tended not to fall as often and that the latency to fall was longer than in nonexercising individuals. Dexterity of upper extremities was also influenced by exercise.9 Similar to muscle strength, forced exercise significantly impacted generalized balance and coordination by decreasing grip time delay, increasing rate of grip force of the manipulating hand, and improving the accuracy of digit placement.
Cognition and exercise An unfortunate consequence of irreversible neurodegeneration in PD is cognitive impairment, which diminishes QOL. Executive function encompasses abstract thinking, mental flexibility, problem solving, organizing logical strategies, planning or carrying out actions, judgment, and controlling behavior.15 A decline in executive function is the most common cognitive deficit and worsens with age and duration of disease.15 Possible causes of diminished executive function are dopaminergic neuron loss that may disrupt the substantia nigro-striatum-thalamus-cortical circuit and imbalance of cholinergic to dopamine activity in the basal ganglia.15 Tanaka and colleagues observed significant improvements in components of executive function on completion of an exercise program.15 Abstract thinking and mental flexibility, ie, the ability to make appropriate decisions under certain circumstances, were the primary subsets affected.
Exercise also results in positive trends in verbal fluency and organization of words and fewer errors in spatial working memory.16 Dibble and colleagues administered the Parkinson's Disease Questionnaire (PDQ-39) to participants at the end of their training period. A standardized self-assessment tool, the PDQ-39 focuses on areas that influence a patient's QOL. These components include cognition, emotion, mobility, performance of ADLs, stigma, social support, communication, and bodily discomfort.10 When PDQ-39 results were compared with those of nonexercisers, patients who exercised felt they saw an improvement in cognitive function.16
Psychological status and exercise Whether attributed to a decline in dopamine within the brain or situational stress resulting from diagnosis of PD, depression is a common finding among PD patients. As previously noted, exercise in healthy people enhances mood by stimulating specific neurotransmitters. Research evaluating the emotional benefits of exercise in PD patients is limited; however, current data are promising. Rodrigues de Paula and colleagues assessed changes in mood of PD patients using the Nottingham Health Profile, a self-evaluation of physical, emotional, and social welfare. Physical activity was shown to have a positive impact on emotion when exercisers were analyzed against controls.17 In addition to enhanced cognitive function, Dibble and colleagues saw improvements in mood when the PDQ-39 results of their training group were compared with those of controls.16
Parkinson disease has become a growing problem worldwide. Within the past decade, scientists have begun to explore nonpharmacologic treatments, especially exercise, as possible adjunct or alternative therapy. The literature discussed in this article presents positive data regarding the impact of exercise on motor, cognitive, and emotional complications. Clinicians should consider recommending activities, such as gait and resistance training, balance/ coordination exercises, continued participation in ADLs, and tandem cycling, to individuals with mild and moderate PD. The long-term effect of exercise and its impact on later stages of the disease are still unknown. In vivo studies examining the role of exercise on brain chemistry in PD should also be considered in order to better understand the mechanism behind improvement of symptoms.
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