Accelerometers may be reliable tool for measuring ALS disease progression

Key takeaways:

• 97 individuals with MS wore an actigraph for 3 to 7 days every 2 to 3 months for up to 24 months.
• The Vertical Movement Index is a reliable tool for measuring predicted disease progression rates.

Wearable accelerometers may be a reliable tool to track disease progression in patients with amyotrophic lateral sclerosis, researchers wrote in The Lancet.

“Previous studies have demonstrated that accelerometer-derived outcomes using passive monitoring are able to describe disease progression in patients with ALS,” Jordi W. J. van Unnik, MS, a doctoral student in the department of neurology at UMC Utrecht Brain Center, University Medical Center Utrecht in the Netherlands, and colleagues wrote. “However, there has been little attention to whether these outcomes accurately differentiate between rates of disease progression.”

Van Unnik and colleagues sought to evaluate the ability of an accelerometer-derived outcome to detect differential disease progression and assess longitudinal associations with overall survival in patients with ALS, proving its efficacy as a diagnostic tool.

Their study acquired data from two prospective cohort studies conducted between September 2016 and January 2023 at the University Medical Center in the Netherlands.

Participation required 97 individuals (70.1% male) with ALS to wear the ActiGraph GT9X Link, a hip-placed accelerometer, for 3 to 7 days every 2 to 3 months, with a maximum follow-up of 18 to 24 months. The total time that participants wore the device was 27,701 hours across 1,995 days, with a wear-time adherence of 91.8% across both cohorts.

A primary accelerometer-derived outcome, the Vertical Movement Index (VMI), was calculated along with predicted disease progression rates, then analyzed with overall survival.

Clinical utility of VMI was subsequently evaluated using comparisons to patient-reported functionality, while the impact of various monitoring schemes on empirical power was explored through simulations.

Results showed that patients in the first cohort recorded a longer symptom duration than patients in the second (median of 24.9 months vs. 18.5 months).

The VMI was “highly discriminatory” for predicted disease progression rates, revealing faster rates of decline in patients with a worse predicted prognosis compared to those with a better predicted prognosis (P < 0.0001), the researchers wrote. The VMI additionally saw an average rate of decline per month of 0.028 units (95% CI, -0.035 to -0.02), indicating the potential of VMI to reflect different disease progression rates between patients.

The VMI was also strongly associated with the hazard for death (HR = 0.2; 95% CI: 0.09–0.44), where a decrease of 0.19–0.41 units was associated with reduced ambulatory status.

“We have shown that an outcome derived from passive hip-worn accelerometry was highly discriminatory in disentangling differential disease progression rates,” van Unnik and colleagues wrote. “Supporting its use as an outcome measure for ALS clinical trials.”