Psychomotor slowing alters gait velocity, cadence, and stride length and indicates negative symptom severity in psychosis

Abstract

Schizophrenia is a severe mental disorder, in which 50% of the patients present with motor abnormalities such as psychomotor slowing. Slow spontaneous gait has been reported in schizophrenia. However, comprehensive objective instrumental assessments of multiple gait conditions are missing. Finally, the specific gait patterns of subjects with psychomotor slowing are still unknown. Therefore, this study aimed to objectively assess multiple gait parameters at different walking conditions in patients with schizophrenia with and without psychomotor slowing. Also, we hypothesised gait impairments to correlate with expert ratings of hypokinetic movement disorders and negative symptoms. We collected gait data (GAITRite®) in 70 patients with psychomotor slowing (SRRS (Salpetriere retardation rating scale) ≥15), 22 non-psychomotor slowed patients (SRRS < 15), and 42 healthy controls. Participants performed four walking conditions (self-selected speed, maximum speed, head reclined, and eyes closed) and six gait parameters were extracted (velocity, cadence, stride length, functional ambulation profile (FAP), and variance of stride length and time). Patients with psychomotor slowing presented slower velocity, lower cadence, and shorter stride length in all walking conditions compared to healthy controls, with the non-slowed patients in an intermediate position (all F > 16.18, all p < 0.001). Secondly, slower velocity was associated with more severe hypokinetic movement disorders and negative symptoms. In conclusion, gait impairments exist in a spectrum with healthy controls on one end and patients with psychomotor slowing on the other end. Patients with psychomotor slowing are specifically impaired when an adaptation of gait patterns is required, contributing to the deleterious effects of sedentary behaviours.

Fig. 1. Boxplots per group and condition for each gait parameter.

Box represents the interquartile range (IQR; distance between first quartile Q1 to third quartile Q3) with median in between. Whiskers represent the outermost values within Q1 − 1.5×IQR and Q3 + 1.5×IQR. Outliers are plotted individually as circles. Significant differences between groups within the condition are marked with brackets. For comparisons with healthy controls, the results of the main ANCOVA are depicted and for comparisons between patient groups, the results of the second ANCOVA are illustrated. FAP functional ambulation performance score; blue (left): healthy controls; yellow (middle): non-psychomotor slow; red (right): psychomotor slow. *p ≤ .05; **p ≤ .01; ***p ≤ .001.

Fig. 2. Correlation plot between gait parameters and clinical scales across all patients (N = 92).

The size of the dots represents the Spearman correlation coefficient rho; the colour of the dots represents p_corr. For exact rho and p-values see Supplementary Table S8. For raw association data see Supplementary Figs. S2 and S3. N number of participants, mSRRS motoric part of the Salpêtrière Retardation Rating Scale, BFCRS Bush-Francis Catatonia Rating Scale, UPDRS Unified Parkinson Disease Rating Scale Part III, p_corr FDR corrected p-values for multiple comparisons.