Periodic Assessment of Trajectories of Housing, Homelessness, and Health Study (PATHS): Protocol for a Prospective Cohort Study of People Experiencing Homelessness.

Background: The past decade has seen a substantial increase in the number of people experiencing unsheltered homelessness. The unsheltered population faces heightened health and social risks, yet research on their experiences remains limited.

Objective: This paper presents the protocol for the Periodic Assessment of Trajectories of Housing, Homelessness, and Health Study (PATHS), a longitudinal study that leverages mobile phone technology and web-based surveys to track the housing and health trajectories of people experiencing unsheltered homelessness in Los Angeles County.

Methods: Participants were recruited from the Los Angeles County Homeless Count Demographic Survey, an annual representative survey of the county's unsheltered population. Eligibility criteria included being aged ≥18 years, having stayed in an unsheltered location or homeless shelter for at least 1 night in the past month, and residing in Los Angeles County. The study uses a web-based survey platform accessible via mobile phones and provides electronic gift card incentives for participation. Data on housing, health, and social outcomes are collected monthly using trauma-informed, equity-sensitive surveys, designed for diverse literacy levels with a user-friendly interface that includes buffers for sensitive topics.

Results: Since the study launched in December 2021, a total of 2058 individuals have been screened and found eligible. In total, 57.43% (n=1182) of participants completed the baseline survey, of whom 75.47% (n=892) completed at least 1 monthly survey. By December 2024, participants had contributed 7585 monthly surveys (average of 8.5, SD 8.36 per respondent and median of 6, IQR 2-11). Compared to the unsheltered population of Los Angeles County, the PATHS sample overrepresents younger adults aged <40 years (641/1182, 54.23% vs 38.64%) and female participants (507/1182, 42.89% vs 27.74%). Furthermore, the PATHS cohort reports a high burden of health risks relative to the housed population, with 47.3% (422/892) reporting symptoms of anxiety (vs 19.1%), 45.1% (402/892) reporting symptoms of depression (vs 16.4%), 35% (312/892) reporting a disability (vs 12.9%), and 69.4% (619/892) experiencing food insecurity (vs 15.7%).

Conclusions: PATHS offers an innovative platform for real-time monitoring of the housing, health, and service needs of people experiencing unsheltered homelessness in Los Angeles County. By leveraging continuous, in-depth data collection via mobile surveys, PATHS provides valuable insights into the evolving challenges faced by this population. Addressing critical gaps in longitudinal research, PATHS has the potential to drive more informed policy decisions and interventions that improve outcomes for this population considered vulnerable.

International Registered Report Identifier (irrid): DERR1-10.2196/74266.