Although insomnia is reliably associated with anxiety symptoms, aspects of insomnia may differentially relate to one anxiety symptom versus another. Therefore, treatment for insomnia comorbidity with anxiety might be individually tailored to optimize treatment response. Working from this hypothesis, we analyzed data from a survey of 1007 community-dwelling adults. Insomnia was measured using the Insomnia Severity Index (ISI), categorizing items as nighttime disturbances, daytime dysfunction, or self-perceived dissatisfaction. Anxiety symptoms were measured with the Generalized Anxiety Disorder 7-item questionnaire (GAD-7). Linear and binomial logistic regression were used and adjusted for covariates. Post hoc forward stepwise analyses determined which components of the insomnia contributed to individual anxiety symptoms. Significant associations between nighttime disturbance (β = 0.88 [0.44, 1.3]), daytime dysfunction (β = 1.30 [0.81, 1.80]), dissatisfaction (β = 1.20 [0.60, 1.7]) and total GAD-7 score were maintained after adjusting for covariates. Nighttime disturbance was associated with excess worrying, restlessness, irritability, and fear of catastrophe. Daytime dysfunction was associated with all symptoms except for fear of catastrophe, and self-perceived dissatisfaction was associated with all symptoms except irritability. Stepwise analyses revealed that daytime dysfunction and dissatisfaction were most consistently related to anxiety symptoms.Greater attention should be paid to daytime dysfunction in patients with insomnia and anxiety, as improving daytime functioning may improve anxiety.
Keywords: anxiety; daytime dysfunction; insomnia; short sleep; sleep health.