Parkinson’s disease (PD) is the second-most common chronically progressive neurodegenerative disease worldwide. PD is associated with the degeneration of dopaminergic neurons and is clinically characterized by resting tremor, rigidity, bradykinesia, and postural instability^1,2). The cause of PD is multifactorial, including a combination of genetic and environmental factors, but the exact cause is unknown¹⁾. Pathologic features include the death of melanin-containing dopaminergic neurons in melancholy densities. Diagnosis of PD is possible only by pathologic examination through autopsy or clinical findings. Treatment with levodopa, a precursor of dopamine, is the most effective treatment for PD to date, although non-pharmacological adjuvant therapies and surgical therapies are available¹⁾. However, there is no definitive treatment for PD. Furthermore, the long-term use of levodopa has adverse effects, the surgical outcome is poor, and the outcome of drug therapy has not improved^1,3).

Therefore, the interest in complementary and alternative medicine (CAM) for PD therapy in substitution for conventional therapies is increasing. More than 40% of PD patients in the United States and Europe are using CAM, and an even higher percentage is using CAM in Europe and Asia^4,5). Acupuncture treatment (AT) is one of the most commonly used treatment modalities for PD patients, and the greatest advantage is the absence of adverse effects and acupuncture does not affect drug response. Despite these advantages, the methodological deficiencies that limit the effectiveness of AT remain unknown because of the lack of objective criteria⁷⁾. The preclinical studies that demonstrated the effectiveness of AT, including those by Kang et al.⁸⁾, Liu et al.⁹⁾, and Wattanathorn et al.¹⁰⁾, serve as the basis for clinical research and are useful for the development of new treatment methods. However, the analysis of intervention methods in human studies is essential, to improve the quality of life and promote health¹¹⁾.

The purpose of this study was to investigate the effect of AT in the tendency of increase of the need for AT for the treatment of PD worldwide and to investigate the advancements in AT research in Korea and the future directions of research in this field.

PD is the second most common neurodegenerative disease after Alzheimer’s disease. The most common clinical symptoms are motor symptoms, including bradykinesia, rest tremor, rigidity, and postural and gait impairment. Non-motor symptoms include neuropsychiatric features, dysautonomia, sleep disorders, sensory dysfunction, pain, and fatigue, and the prevalence of these symptoms is increasing²⁹⁾. At present, drug therapy based on levodopa, a precursor of dopamine, is the treatment of choice for PD. However, the amount of levodopa or dopamine agonist usually is increased during therapy as PD advances because the disease is progressive and levodopa does not prevent disease progression. Symptoms such as non-motor wearing-off and motor fluctuations may occur with the long-term use of levodopa. Dopamine agonists may cause adverse effects such as nausea, vomiting, orthostatic hypotension, leg swelling, anorexia, and sleepiness¹⁾.

Although AT is one of the most commonly used alternative therapies for PD, few studies evaluated the effects of AT in PD patients⁶⁾. Park et al³⁰⁾ and Kang et al³¹⁾ reported that AT prevented 6-hydroxydopamine-induced neuronal death and inhibited microglial activation in PD animal models. Bee venom AT was also associated with neuroprotection^32,33). In addition, Jia et al³⁴⁾ reported that AT improved the motor symptoms of PD by normalizing GABA levels in the midbrain. Other studies demonstrated the effect of AT on PD in animal models. However, Lee et al⁷⁾ and Baek et al³⁵⁾ found no evidence of the effectiveness of AT, EA, and scalp acupuncture on PD. In fact, few studies evaluated the effectiveness of AT in PD patients^6,19).

Of the screened original studies, ten were conducted in China, including nine RCTs and one clinical trial, in which AT was used and the control group was screened; 3 RCTs, 1 pilot study, were conducted in the United States, two RCTs were from Korea, and one RCT was from Brazil. Few intervention studies from Korea evaluated the effectiveness of AT in PD treatment. The retrieved articles were classified by the duration of PD, sample size, evaluation methods, intervention group, and control group. The most common interventions were EA (N=9) and, in these cases, the frequency was set to 4 Hz or 100 Hz or to a frequency that the patient could withstand. In 12 of the 17 original studies, AT was combined with drug therapy using Madopar or levodopa, and no adverse effects were observed in the evaluated studies. In this context, Ren et al²⁰⁾ suggested that AT might be effective in reducing the dosage of drugs used in PD treatment. Six original studies used AT alone and two studies used pharmacoacupuncture. Liu et al¹³⁾ injected kakkonein extract into Fengchi (GB20) in combination with drug therapy to improve patient’s behavior, emotion, and activities of daily living, and observed short-term and long-term benefits. Moreover, Cho et al¹⁶⁾ reported that bee venom AT was a promising adjunctive therapy for PD by injecting 0.1 mL of bee venom (0.001%) into acupoints Fengchi (GB20), Quchi (LI11), Yanglingquan (GB34), Zusanli (ST36), and Taichong (LR3).

The most commonly used acupoints and meridians in the intervention groups were GV20 (7 studies), followed by LR3, ST36, SP6, and GB34. GB and GV were the most commonly used meridians (8 studies). These acupoints and meridians should be used as a criterion for the selection of high-quality studies on AT for PD patients.

The UPDRS³⁶⁾ is the most widely used scale to assess the effect of clinical interventions on PD. It has four sections (I to VI), and section III evaluates motor functions³⁷⁾. UPDRS III is used most often because the total UPDRS score is inefficient in many cases. Although it was used in most screened studies (9 out of 17), UPDRS III does not evaluate the effect of AT on PD, and thus a new standard should be developed^38,39). Some studies reported that the evaluation of the effect of AT on PD is limited by the sample size^7,35,40). In addition, the effectiveness of AT could be assessed because the quality of the studies was poor. Therefore, high-quality clinical studies are necessary to evaluate the effectiveness of AT and thus provide valuable information to physicians and patients. The methodological deficiencies can be overcome by using Consolidated Standards of Reporting Trials (CONSORT)⁴¹⁾ and Standards for Reporting Interventions in Clinical Trials of Acupuncture (STRICTA)⁴²⁾ to ensure the quality of research.

The purpose of this study was to provide directions for research on AT in PD patients in Korea by reviewing national and international intervention studies.