Age at Onset in Adults with Insomnia: A Latent Profile Analysis

Age at Onset in Adults with Insomnia: A Latent Profile Analysis

Introduction
Research has sought to understand insomnia through identification of subtypes, yet age at onset (AAO) has received limited empirical attention. Across psychiatric disorders, early AAO is associated with higher clinical severity and burden, more persistent course, and greater familiality, whereas late AAO is associated with comorbid psychiatric and physical illness. We sought to detect clinically distinct AAO subgroups in adults with insomnia utilizing latent profile analysis (LPA).

Methods
Participants were 618 adults aged 18 to 71 years (M=28.94, SD=11.06) with insomnia, recruited through Prolific Academic. Participants completed an internet survey of demographics, medical/psychiatric history, family history, insomnia onset acuity, and course, causal attributions surrounding insomnia onset, and current insomnia severity and sleep-related impairment. LPA was performed on AAO of clinically significant insomnia (i.e., causing distress or daytime impairment and occurring 3 days per week for at least 3 months). Independent samples t-test and chi-squared test of independence were performed to compare resulting AAO subgroups on clinical outcomes.

Results
A two-class model (Class 1: n=547, 88.5%, Monset=19.2 years; Class 2: n=71, 11.5%, Monset=43.5 years) was optimal for forming insomnia AAO subgroups. The late onset group had higher relative insomnia severity, t=-2.78, p=.006, and sleep-related impairment, t=-3.75, p<.001. There were no group differences in lifetime prescription sleep medication, p=.569, lifetime diagnosis of psychiatric disorder(s), p=.189, family history of insomnia, p=.159, or insomnia onset acuity (i.e., sudden vs. gradual), p=.140. Late onset was associated with higher relative endorsement of hormonal factors, Χ2=12.81, p<.001, bodily arousal, Χ2=8.57, p=.003, scheduling, Χ2=9.08, p=.003, and childhood experiences and traumatic events, Χ2=5.67, p=.017). There were group differences in insomnia course, Χ2=16.35, p<.001, such that early onset was associated with higher relative endorsement of persistent insomnia and late onset was associated with higher relative endorsement of seasonal insomnia.

Conclusion
Findings suggest the presence of an early onset group with higher persistence, but not increased severity and impairment as anticipated, and a late onset group with more seasonal course, numerous causal attributions, and higher insomnia severity and impairment. Future replication is needed to determine the validity and treatment applications of these subgroups.

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