To determine the prevalence of pre-admission insomnia symptoms among hospitalized patients and assess the association of insomnia symptoms with objective in-hospital sleep and clinical outcomes.
We conducted a prospective cohort study of medicine inpatients (age ≥50, no previously diagnosed sleep disorders). Participants answered the Insomnia Severity Index (ISI) questionnaire to assess for pre-admission insomnia symptoms (scored 0-28, higher scores suggest more insomnia symptoms). Sleep duration and efficiency were measured with actigraphy. Participants self-reported 30-day post-discharge readmissions and emergency department (ED) and/or urgent care visits.
Of 568 participants, 49% had ISI scores suggestive of possible undiagnosed insomnia (ISI ≥8). Higher ISI scores were associated with shorter sleep duration (β=-2.6, 95% CI -4.1 to -1.1, p=0.001) and lower sleep efficiency (β=-0.39, 95% CI -0.63 to -0.15, p=0.001). When adjusted for age, sex, BMI, and co-morbidities, higher ISI scores were associated with longer length of stay (IRR 1.01, 95% CI 1.00-1.02, p=0.011), increased risk of 30-day readmission (OR 1.04, 95% CI 1.01-1.07, p=0.018), and increased risk of 30-day ED or urgent care visit (OR 1.04, 95% CI 1.00-1.07, p=0.043).
Among medicine inpatients, there was a high prevalence of pre-admission insomnia symptoms suggestive of possible undiagnosed insomnia. Participants with higher ISI scores slept less with lower sleep efficiency during hospitalization. Higher ISI scores were associated with longer length of stay, increased risk of a 30-day post-discharge readmission, and increased risk of a 30-day post-discharge ED or urgent care visit.

© 2023 American Academy of Sleep Medicine.