# Redefining Insomnia: A Comparison of Categorical and Dimensional Approaches

> **NIH NIH R01** · UNIVERSITY OF PENNSYLVANIA · 2024 · $736,018

## Abstract

Project Summary
Insomnia is the most common sleep disorder and negatively impacts daily functioning, quality of life, and work
productivity. Despite the high prevalence of insomnia, particularly in women, and >40 years of extensive
research efforts, the field still lacks a solid understanding of how insomnia should be assessed and defined.
For example, polysomnography (PSG) has failed to yield a consistent pattern of objective impairment and, in
fact, often fails to distinguish individuals with insomnia from good sleepers. Clinical diagnosis of Insomnia
Disorder is therefore based solely on subjective report of difficulty initiating or maintaining sleep (DIMS)
associated with perceived distress or impairment. Earlier diagnostic editions differentiated multiple subtypes
based on patterns of clinical symptoms that failed to demonstrate reliability and validity and have since been
abandoned. Insomnia is now operationalized as a monolithic subjective entity despite the likelihood that it is
instead a heterogeneous disorder with multifactorial etiology and presentation with complexity akin to
depression. Heterogeneity significantly reduces the likelihood of understanding the pathophysiology of
insomnia or realizing a goal of personalized insomnia treatment. We propose that the time is ripe for a
reconceptualization that combines knowledge about subjective and objective DIMS with mechanistic factors
known to be associated with insomnia: hyperarousal and circadian misalignment (i.e. sleeping out of phase
with endogenous rhythms). To that end, this proposal seeks to revisit the operationalization of insomnia to
derive a classification system with high reliability and validity. We will recruit n=400 individuals with subjective
DIMS, defined as sleep onset latency, wakefulness after sleep onset, and/or early morning awakenings >30
minutes. Following home sleep apnea screening, in depth phenotyping will assess four constructs of insomnia:
1) subjective DIMS based on sleep diaries and retrospective self-report; 2) objective DIMS with actigraphy and
home PSG; 3) physiologic (heart rate variability), cognitive (self-report) and cortical (beta EEG) hyperarousal;
and 4) circadian misalignment defined as the phase angle between dim light melatonin onset and midpoint of
sleep along with subjective and actigraphic measures of rhythmicity. Structural equation modeling and latent
profile analysis will be used to both derive latent factors underlying each dimension (dimensional model) and to
categorize individuals into distinct subgroups based on these inputs (categorical model). Reliability will be
examined in a subset (n=200) by conducting a second assessment one month later to assess for temporal
stability of categories and dimensions. Concurrent validity of each dimension and category will be assessed by
examining associations with validators of subjective distress, mental health symptoms, quality of life,
neurocognitive performance and peripheral inflammation.

## Key facts

- **NIH application ID:** 10855650
- **Project number:** 1R01HL173043-01
- **Recipient organization:** UNIVERSITY OF PENNSYLVANIA
- **Principal Investigator:** Philip Richard Gehrman
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $736,018
- **Award type:** 1
- **Project period:** 2024-07-15 → 2028-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10855650

## Citation

> US National Institutes of Health, RePORTER application 10855650, Redefining Insomnia: A Comparison of Categorical and Dimensional Approaches (1R01HL173043-01). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10855650. Licensed CC0.

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