Assessing Physical Activity in People with Mental Illness: 23-Country Reliability and Validity of the Simple Physical Activity Questionnaire (SIMPAQ)

Background: Physical inactivity is a key contributor to the global burden of disease and disproportionately impacts the wellbeing of people experiencing mental illness. Increases in physical activity are associated with improvements in symptoms of mental illness and reduction in cardiometabolic risk. Reliable and valid clinical tools that assess physical activity would improve evaluation of intervention studies that aim to increase physical activity and reduce sedentary behaviour in people living with mental illness. Methods: The five-item Simple Physical Activity Questionnaire (SIMPAQ) was developed by a multidisciplinary, international working group as a clinical tool to assess physical activity and sedentary behaviour in people living with mental illness. Investigators from 43 centres in 23 countries collected reliability and validity data on the SIMPAQ from patients with DSM or ICD mental illness diagnoses. Test-retest repeatability was assessed one-week apart. Criterion SIMPAQ validity was assessed against accelerometer-derived measures of physical activity. Findings: Data were obtained from 1,010 participants. The SIMPAQ had good test-retest reliability (Spearman rho approximately 0.70). Criterion validity for moderate-vigorous physical activity was comparable to studies conducted in general population samples. Criterion validity of the sedentary behaviour item was poor. An alternative method to calculate sedentary behaviour had greater criterion validity. This alternative method is recommended for use in future studies employing the SIMPAQ. Interpretation: The SIMPAQ is a brief measure of physical activity and sedentary behaviour that can be reliably and validly administered by health professionals. Funding Statement: SR is funded by an NHMRC Early Career Fellowship (APP1123336). BS is supported by Health Education England and the National Institute for Health Research HEE/ NIHR ICA Programme Clinical Lectureship (ICA-CL-2017-03-001). FG and BS are part supported by the Maudsley Charity and the National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care South London (NIHR CLAHRC South London) at King’s College Hospital NHS Foundation Trust with support from the National Institute for Health Research (NIHR) Biomedical Research Centre at South London and Maudsley NHS Foundation Trust. The views expressed in this publication are those of the authors and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health and Social Care. JBA was supported by the Spanish Ministry of Education (FPU13/05130). Declaration of Interests: We confirm that authors have no competing interests. Ethics Approval Statement: Approval was obtained from the Human Research Ethics Committee (HREC) of UNSW Sydney, Australia (HC15586) as the lead site. Details of individual site ethics approvals from participating sites are listed in Supplementary material.