Quantitative associations between objective sleep measures and early-morning mobility in Parkinson's disease: cross-sectional analysis of the PHASE study.

STUDY

OBJECTIVES

Previous studies have suggested associations between sleep measures and early-morning akinesia; however, objective evidence is limited. The purpose of this study was to evaluate the associations between objective sleep measures and morning mobility among patients with Parkinson's disease (PD).

METHODS

In this cross-sectional study, we measured objective sleep parameters and morning mobility in 157 patients with PD (mean age, 71.4 years) for six consecutive days using an actigraph placed on the nondominant wrist. Low morning mobility was defined as less than 100 counts/min within the first 2 hours after rising.

RESULTS

The mean duration of low morning mobility was 55.7 minutes (SD, 23.8), and the mean sleep parameters were as follows: sleep efficiency (SE), 72.1% (13.6); wake after sleep onset (WASO), 104.7 minutes (57.9); total sleep time (TST), 343.6 minutes (104.0); and fragmentation index (FI), 3.5 (3.4). Multivariable linear regression analysis adjusted for potential confounders demonstrated significant associations between better objective sleep measures and shorter low morning mobility (SE per %: β, -0.419; 95% CI = -0.635 to -0.204; p < 0.001; WASO per min: β, 0.056; 95% CI = 0.003 to 0.109; p = 0.039; and FI per unit; β, 1.161; 95% CI = 0.300 to 2.023; p = 0.009) but not TST (p = 0.78). These findings were not altered by different cutoff values of mobility (50 counts/min) or duration (1 h after rising).

CONCLUSIONS

In patients with PD, better objective sleep measures are significantly associated with shorter low morning mobility. Future studies investigating whether improved sleep reduces symptoms of low morning mobility are required.