Markus J. Duncan’s PhD Thesis Defence – Oct 22

Title: “Assessing Physical Activity and Sedentary Behaviour in Individuals with Schizophrenia”

Supervisory Committee: Dr. Guy Faulkner (Research supervisor), Dr. Alasdair Barr (Anesthesiology, Pharmacology & Therapeutics), Dr. Mark Beauchamp (Kinesiology)
University Examiners: Dr. Jean-Sebastien Blouin (Kinesiology), Dr. Donna Lang (Radiology)
External Examiner: Dr. Simon Rosenbaum (University of New South Wales)
Chair: Dr. Paul Pavlidis (Psychiatry)

Abstract: Individuals with schizophrenia have a greatly reduced life expectancy compared to the general population due in part to higher rates of diabetes, obesity, and cardiovascular disease. Individuals with schizophrenia also engage in lower volumes of physical activity and engage in more sedentary behaviour, which contributes to poor overall health. Evaluating time spent in such movement behaviours accurately is necessary to engage in all phases of behavioural epidemiology and for developing interventions to induce behaviour change.

This dissertation evaluates whether the most commonly used self-report questionnaire, the International Physical Activity Questionnaire (IPAQ), for measuring time spent in physical activity (Chapter 2) and sedentary behaviour (Chapter 3) among people with schizophrenia is an accurate representation of movement behaviours in people with schizophrenia compared to accelerometry derived scores.

After quantifying the discrepancy between measurement methods, Chapter 4 explores individual level correlates of this discrepancy to understand what factors may contribute to less accurate IPAQ scores, and regression-calibration adjustments to IPAQ scores were evaluated using a 5-fold cross-validation approach as a possible method to improve score accuracy.

Subsequently, Chapter 5 assesses whether accelerometry protocols were adhered to consistently in the sample and accelerometry data were used to evaluate the composition of movement behaviours in this sample across the week; an isotemporal substitution approach is used to determine whether replacing one movement behaviour with another (e.g. sedentary behaviour with moderate intensity physical activity) is associated with health and demographic factors while controlling for all other movement behaviours. The results of these studies suggests that IPAQ scores should no longer be used as a measure of time spent in movement behaviours in individuals with schizophrenia; researchers and medical professionals are recommended to use more direct methods of movement measurement such as accelerometry or leverage the already widespread adoption of consumer smart devices to collect movement behaviour data that better represents how individuals with schizophrenia spend their waking day.