JMIR Publications

ABSTRACT

Background:

Heightened stress and insufficient sleep are common in the transition to college, often co-occur, and have both been linked to negative health outcomes. A challenge concerns disentangling the temporal directionality of their associations in daily life. Prior research has reported inconsistent findings, with changes in perceived stress preceding and/or succeeding changes in sleep duration. One possibility is that these day-to-day associations vary across individuals, but short study periods and group-level analyses may have obscured person-specific phenotypes.

Objective:

We present a precision approach to the study of day-to-day associations between perceived stress and objective sleep duration that leverages intensive longitudinal data collected via wearables and smartphones. We developed an individual-level linear model (iLM) that provides stable, individually tailored estimates unbiased by the group. The model was designed to be parsimonious while accounting for the non-independence and temporal structure of the data.

Methods:

Fifty-five college students sampled continuously for a full academic year provided daily self-reports of perceived stress via a smartphone app and wore an actigraphy wristband for the estimation of daily sleep duration (median usable daily observations per participant = 178). We developed and validated the iLM framework on a pilot subset of six participants that was fully independent from the target sample. In addition to the predictor of interest, the model included a covariate for day of the week to account for weekly patterns. The model was tested by applying it to variables expected to be strongly correlated with each other: objective sleep duration and self-reported quality of the same sleep event. Adequacy of the model specification was confirmed through several diagnostic tests. The model was then applied to the target sample of 49 first-year college students for the examination of bi-directional associations between daily stress levels and sleep duration.

Results:

Proof-of-concept analyses captured expected associations between objective sleep duration and subjective sleep quality and passed all model diagnostics. Target analyses revealed negative associations between sleep duration and perceived stress in most individuals. Critically, our participants represented all the phenotypes of temporal association identified in prior literature: for some, elevated stress in the day was associated with shorter sleep later that night; for others, shorter sleep was associated with elevated stress the next day; others showed both directions of associations, and some showed no association. Of note, when modeled using a group-based, multilevel model, individual estimates were systematically attenuated, and some even sign-reversed.

Conclusions:

The dynamic interplay of stress and sleep in daily life is likely person specific. Paired with intensive longitudinal data, our individual-level model provides a precision framework for the estimation of stable real-world behavioral and psychological dynamics, and may support the personalized prioritization of intervention targets for health and wellbeing.