Abstract
Mobility is an important correlate of physical, cognitive, and mental health in chronic illness, and can be measured passively with mobile phone global positional satellite (GPS) sensors. To date, GPS data have been reported in a few studies of schizophrenia, yet it is unclear whether these data correlate with concurrent momentary reports of location, vary by people with schizophrenia and healthy comparison subjects, or associate with symptom clusters in schizophrenia. A total of 142 participants with schizophrenia (n = 86) or healthy comparison subjects (n = 56) completed 7 days of ecological momentary assessment (EMA) reports of location and behavior, and simultaneous GPS locations were tracked every five minutes. We found that GPS-derived indicators of average distance travelled overall and distance from home, as well as percent of GPS samples at home were highly correlated with EMA reports of location at the day- and week-averaged level. GPS-based mobility indicators were lower in schizophrenia with medium to large effect sizes. Less GPS mobility was related to greater negative symptom severity, particularly diminished motivation, whereas greater GPS mobility was weakly associated with more community functioning. Neurocognition, depression, and positive symptoms were not associated with mobility indicators. Therefore, passive GPS sensing could provide a low-burden proxy measure of important outcomes in schizophrenia, including negative symptoms and possibly of functioning. As such, passive GPS sensing could be used for monitoring and timely interventions for negative symptoms in young persons at high risk for schizophrenia.
Highlights
There continues to be a great need for objective, collected measures of symptoms and functional outcomes in schizophrenia research[1]
The purpose of this study was to: (a) validate mobility indicators derived from global positioning system (GPS) relative to ecological momentary assessment (EMA) data based on reports of physical location; (b) compare GPS-derived mobility between people with diagnoses of schizophrenia and healthy comparators, and (c) examine associations within the group with schizophrenia between GPS-derived mobility information and in-lab data collected on symptoms, cognitive performance, and functional measures
We investigated GPS-derived metrics of mobility in people with schizophrenia and found, as hypothesized, that people with schizophrenia spent more time at-home, traveled shorter distances overall and shorter distances away from home over 1 week of sampling than healthy comparators, and the magnitude of these differences were large
Summary
There continues to be a great need for objective, collected measures of symptoms and functional outcomes in schizophrenia research[1]. The purpose of this study was to: (a) validate mobility indicators derived from GPS relative to EMA data based on reports of physical location; (b) compare GPS-derived mobility between people with diagnoses of schizophrenia and healthy comparators, and (c) examine associations within the group with schizophrenia between GPS-derived mobility information and in-lab data collected on symptoms, cognitive performance, and functional measures. Persons with greater disability and cognitive impairment tend to travel smaller distances from home as measured by GPS data[9,10,11,12], yet this construct has not been empirically examined in schizophrenia either through questionnaire or GPS data. Related functional constructs in schizophrenia such as community participation and mobility have been evaluated in schizophrenia research through self-reported and informant-based surveys, and reduced mobility indexed by these constructs are predicted by cognitive ability, physical illnesses, and negative symptoms[13,14]
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