The Effects of Anxiety and Cognitive Load on Freezing of Gait in Parkinson's Disease

It is currently unclear whether anxiety, cognitive load, or their combination modulates freezing of gait differently and whether people with Parkinson's disease and freezing of gait (freezers) suffer from stronger threat responsiveness than nonfreezing groups. Therefore, we investigated 28 freezers, 19 nonfreezers, and 19 healthy age-matched controls, who completed a freezing-provoking protocol under different conditions. State anxiety was generated via a threat of shock or a threat of freezing paradigm. Cognitive load was imposed via a dual task. The primary outcome was the freezing ratio, derived from wearable sensors. Stress was monitored by self-reported and physiological markers. Freezers had worse cognition and more severe motor symptoms than nonfreezers yet a similar trait anxiety and threat response compared with both nonfreezing groups. Anxiety and cognitive load tended to increase the freezing ratio across groups. When combined, anxiety and cognitive load showed no surplus effects. Compared with the threat of shock, the threat of freezing had less impact on the freezing ratio, and although it induced less perceived stress, it generated higher physiological stress responses. In conclusion, freezers showed overall comparable levels of trait anxiety and a similar threat response as nonfreezers and healthy controls. Anxiety and cognitive load each tended to increase the freezing ratio, but their combined effect seemed to plateau. The threat of freezing had a smaller effect than the threat of shock as the former may not have diverted the attention away from walking to the same degree as the latter, although this explanation remains speculative.