Who is at risk for having persistent insomnia symptoms? A longitudinal study in the general population in Korea.

Objectives: Our study had three goals: (1) to investigate the longitudinal course of insomnia symptoms over 4 years (3 time points) by analyzing the trajectory of insomnia symptoms for all participants, (2) to compare persistent insomnia symptom to nonpersistent insomnia symptom groups on mental health and quality of life (QoL), and (3) to conduct exploratory analyses on the relative contribution of multiple factors to persistence of insomnia symptoms.

Methods: Our population-based longitudinal study utilized a community-based sample from the Korean Genome and Epidemiology study (KoGES). Participants were 1247 individuals (40.1% men; mean age, 54.3±7.1 years). Insomnia, QoL (measured by 12-item Short-Form health survey [SF-12]), sleep-interfering behaviors, and depression (measured by the Beck Depression Inventory [BDI]) were followed with biennial examinations at 3 data points spaced 2 years apart (baseline, time 1, and time 2).

Results: Among individuals experiencing insomnia symptoms at baseline, the most common trajectory was to experience persistent nocturnal insomnia symptoms across all 3 time points. Those with persistent insomnia symptoms had significantly lower physical and mental QoL (measured by SF-12) and higher depression (measured by BDI) at time points compared to those without persistent nocturnal insomnia symptoms. A follow-up exploratory receiver operating characteristic curve (ROC) analysis identified poor sleep quality, frequent sleep-interfering behaviors, and low mental health QoL as the strongest predictors of persistent insomnia symptoms above other well-known risk factors.

Conclusions: In particular, an interaction between poor sleep quality, sleep-interfering behaviors, and mental health QoL appeared to be the strongest risk factor for persistent insomnia symptoms.