Among European Individuals with Major Depressive Disorder, Higher Severity of Insomnia Symptoms Is Independently Associated with Poorer Health-Related Outcomes

OBJECTIVES: While insomnia is a common symptom of major depressive disorder (MDD), the impact of insomnia symptom severity on health-related outcomes in MDD is not well understood. This study evaluated the relationship between insomnia symptom severity and health-related outcomes among individuals with MDD in 5 European countries.

METHODS: Retrospective, cross-sectional data from the 2020 National Health and Wellness Survey conducted in France, Germany, UK, Italy, and Spain were utilized to identify individuals who self-reported a depression diagnosis and experienced insomnia in the past 12 months (n = 3396). Insomnia symptom severity was measured with Insomnia Severity Index (ISI); higher scores correspond to more severe insomnia. Measured outcomes included: depression (Patient Health Questionnaire-9); anxiety (Generalized Anxiety Disorder Assessment-7); daytime sleepiness (Epworth Sleepiness Scale); medication adherence (Medication Adherence Reasons Scale); healthcare resource utilization; health-related quality of life (HRQoL; SF12v2 mental [MCS] and physical component [PCS] summary, EQ-5D visual analog scale [EQ VAS]); work productivity and activity impairment; direct and indirect costs. Multivariable analyses assessed the association of ISI score with outcomes, while controlling for sociodemographic and clinical variables.

RESULTS: Mean ISI score was 15.4 (range: 0-28); higher ISI was associated with greater depression severity (r=0.53, p<0.001). After adjustments, higher ISI scores were significantly associated with higher levels of depression (rate ratio [RR]=1.05), anxiety (RR=1.04), daytime sleepiness (RR=1.01), and medication non-adherence (RR=1.06), more healthcare provider visits (RR=1.02), emergency room visits (RR=1.02), and hospitalizations (RR=1.04), greater absenteeism (RR=1.07), presenteeism (RR=1.03), overall work productivity impairment (RR=1.03), and non-work-related activity impairment (RR=1.03); higher direct (RR=1.04) and indirect (RR=1.04) costs, and poorer HRQoL (MCS: β=-0.464; PCS: β=-0.373; EQ VAS: β=-1.108), all p<0.01.

CONCLUSIONS: In patients with MDD, higher levels of insomnia are associated with worse health-related outcomes. These results suggest that MDD treatments that better target insomnia symptoms in individuals with depression may improve health-related outcomes.