Uncovering the benefits of physical activity in Huntington's disease: A closer look at the PACE-HD

The effects of long-term physical activity on Huntington's disease patients are unclear due to limited research. However, recent findings from the PACE-HD study have shed light on this issue. The study specifically focused on the effects of a physical activity intervention, guided by a physical therapist, on the quality of life of patients who were a part of a larger clinical trial.

In this blog, we will delve into the results of the PACE-HD study to uncover its most significant clinical implications.

But first, let's recap what Huntington’s disease is

Huntington's disease is a neurological disability that results from a faulty gene. Individuals with a mutation in the huntingtin gene suffer from a triad of symptoms - abnormal movements, mental health problems and lower cognition- which worsens with time [1].

The most important of these symptoms is chorea which is unintended, jerky movements of the arms, legs and face. As the disease progresses, patients suffer from Parkinson's disease-like symptoms, such as difficulty initiating intended movements.

Besides movement difficulties, patients suffer from anxiety, irritability, depression, apathy, and cognitive decline. The disease progresses relentlessly and the patients face an extreme drop in their quality of life and a lack of purpose.

Current treatment of Huntington’s disease

The current treatment for Huntington's disease only focuses on relieving symptoms and does not stop or reverse the progression of the disease. The drugs used to control symptoms are often ineffective and they can sometimes worsen other symptoms [2]. As a result, patients with Huntington's disease still have a low quality of life even with aggressive treatment. Healthcare providers often look for other options to improve their quality of life. Physical therapy has proven to be the most effective and attractive option in this regard.

Revamping Huntington’s disease treatment: the importance of physical therapy

Contrary to expectations, the advent of new treatments for a debilitating disorder has only highlighted the crucial role of physical therapy. Studies show that physical activity, including exercise, can enhance the effects of novel treatments like cell replacement therapy. This underscores the importance of further research into the benefits of stand-alone and adjunct physical therapy to maintain a good quality of life and independence.

Additionally, physical therapy-based interventions can take a long time to produce noticeable results and require a sustained commitment to see any change. To fully understand the benefits of physical therapy, it must be studied in patients without symptoms over an extended period to reach reliable conclusions.

Description of PACE-HD study

This study recruited participants that had:

• A confirmed genetic diagnosis of Huntington's disease

• Been over 18 years old

• Been a participant in another study called Enroll-HD

• Early-mid stage disease

A subset of participants were taken from the Enroll-HD study and were randomly assigned to either the intervention or the control group [3]. Both participants and assessors were not blinded to allocation. Participants in the intervention group developed activity goals with the therapist and were given wearable activity monitors to monitor the physical activity. In contrast, participants in the control group continued with their usual level of physical activity. Participants in both the groups kept monthly diaries to record the amount and types of physical activities and falls. The patients remaining in the original Enroll-HD study received no interaction beyond baseline and follow-up assessments.

The participants were given physical activity intervention guided by trained physical therapists to promote engagement in physical activity, especially aerobic exercise. This intervention consisted of up to 18 sessions over 12 months and used a disease-specific workbook and self-determination theory for participant-coach interactions. The timing and location of sessions were determined between the participant and therapist; if in-person visits were not possible, therapists conducted sessions via video conferencing or phone calls.

What did it show?

The study gave the following outcomes:

• It demonstrated the feasibility of a nested trial within cohort design that brings with it potential advantages for a rare disease like Huntington's disease.

• As expected in a neurodegenerative condition, the cohort group's performance-based measures and self-reported physical activity declined over the 12-month period.

• There were differences between the groups in favor of the intervention group for assessments with more than 60% data completion at 12 months for predicted aerobic fitness, 6-min walking, and self-reported physical activity [4].

Takeaway points

• Physical activity can be combined with current treatment to increase the quality of life for Huntington's disease.

• PACE-HD study shows that long-term physical activity has a benefit in terms of performance-based measures and self-reported outcomes.

• This study also paves the way for further investigations following the same nested trial within cohort design.

References

1. Ghosh, R. et al. 'Clinical Features of Huntington's Disease'. Adv Exp Med Biol. (2018) 1049, 1–28. DOI: 10.1007/978-3-319-71779-1_1.

2. Estevez-Fraga, C. et al. 'Therapeutic strategies for Huntington's disease'. Curr Opin Neurol. (2020) 33(4), 508–518. DOI: 10.1097/WCO.0000000000000835.

3. Sathe, S. et al. 'Enroll-HD: An Integrated Clinical Research Platform and Worldwide Observational Study for Huntington's Disease'. Frontiers in Neurology. (2021) 12.

4. Quinn, L. et al. 'Physical activity and exercise outcomes in Huntington's disease (PACE-HD): results of a 12-month trial-within-cohort feasibility study of a physical activity intervention in people with Huntington's disease'. Parkinsonism & Related Disorders. (2022) 101, 75–89. DOI: 10.1016/j.parkreldis.2022.06.013.