Abstract
Background
Motor abnormalities frequently occur in schizophrenia along with hallucinations, delusions, and negative symptoms. Psychomotor slowing (PS) is one of these motor abnormalities and is characterized by reduced levels of spontaneous gross motor activity as measured by actigraphy, slowed gait and slowing in fine motor tasks. Several reports indicated that 30–50% of schizophrenia patients are suffering from PS. Moreover, PS is associated with multiple disadvantages such as sedentary behavior, cardiometabolic risks and predicts poor treatment outcome and long-term cognition deficits. Therefore, there is a need to accurately and reliably evaluate PS in clinical settings.
In the current study, we anaylized how the gold-standard actigraphy corresponds to either self-report or expert ratings.
Methods
In the present study, we evaluated the motor behavior of 23 patients suffering from schizophrenia spectrum disorders and 17 healthy controls using 3 distinct methods. (i) An observer rating scale: The Salpêtrière Retardation Rating Scale (SRRS), which is a 15 Items-scale ranging from 0 to 60 points measuring PS. A higher score indicates severe impairment. (ii) A self-report Questionnaire: the International Physical Activity Questionnaire (IPAQ), in which the participant report their physical activity. It is a 7 Items-scale, which estimates the weekly metabolic commitment to walk and to perform physical activities of moderate and vigorous intensities. The higher the score, the more active was the person during the last week. (iii) the gold-standard actigraphy, which measures the gross motor activity of the participants for 24h by wearing an actiwatch on the non-dominant arm. It integrates all movements of a subject whithin 24 hours into one parameter.
Results
Both the physical activity measured with wrist activity (t(35) = 3.901, p < .005; controls: m = 349099, sd = 112853; patients: m = 228072, sd = 74639) and the observer rated SRRS-score (t(38) = -15.235, p < .001; controls: m = .41, sd = .62; patients: m = 26.30, sd = 6.96) differed between patients and controls. However, self-reported physical activity did not differ between both groups (t(38) = 1.452, p = .155; controls: m = 4502, sd = 6103; patients: m = 2241, sd = 3727).
There is a trend for a negative correlation between the SRRS-score and the objective activity level, measured by actigraphy, in patients (r = -.378, p = .100). This suggests that patients with the highest SRRS scores indeed presented also the lowest level of global activity. There is also a positive correlation between the objective activity level and the self-reported activity in patients yet lacking statistical significance (r = .337, p = .147). However, there is no correlation between SRRS and IPAQ (r = .204, p = .349) in patients.
Discussion
In this study, we demonstrated that the expert ratings (SRRS) correspond well to the gold standard actigrahpy, even though this association is not significant yet. Thus, expert raters seem to rate PS correctly in patients. However, the self-report (IPAQ) neither corresponds well with the expert ratings nor the actigraphy. Thus, in evaluating PS in psychosis, researchers should not rely on self-report exclusively. Finally, this finding also suggests that patients may not perceive their physical inactivity correctly in case this was due to psychomotor slowing.
Low physical activity is associated with two hypokinetic motor abnormalities in psychosis
