Validation of the French version of the Sleep Inertia Questionnaire (SIQ) and its assessment in sleep disorders.

BACKGROUND

Sleep inertia is a transient state of impaired cognitive and motor performance following awakening, particularly, but not exclusively, observed in central disorders of hypersomnolence (CDH). The Sleep Inertia Questionnaire (SIQ), a 22-item self-report scale assessing behavioral, physical, emotional, and cognitive dimensions, was developed in 2015 in English.

OBJECTIVE

To translate and validate a French version of the SIQ and to evaluate its psychometric properties in patients with CDH or obstructive sleep apnea (OSA).

METHODS

The SIQ was translated using a forward-backward procedure. The French version was administered to adults hospitalized in a tertiary sleep center for OSA or CDH, alongside validated questionnaires assessing fatigue (Pichot), sleepiness (ESS), sleep quality (PSQI), anxiety and depression (HAD-A and HAD-D), chronotype (Horne & Ostberg), and acute sleep inertia (St Mary's Hospital Questionnaire item 6). Psychometric properties assessed were floor/ceiling effects, internal consistency (Cronbach's α and McDonald's ω), construct validity (confirmatory factor analysis), and external validity (Pearson correlations). Sleep inertia characteristics were compared between groups.

RESULTS

We included 237 participants (53.6% women, mean age 46.5 ± 17.5 years, 73% OSA and 27% CDH). The French SIQ demonstrated excellent internal consistency (Cronbach's α = 0.93; McDonald's ω = 0.94) and acceptable construct validity. SIQ scores correlated with fatigue (r = 0.70), anxiety (r = 0.52), depression (r = 0.52), sleepiness (r = 0.51), sleep quality (r = 0.44), acute inertia (r = -0.57), and chronotype (r = -0.52) (all p < 0.001). Patients with CDH had significantly higher SIQ scores and longer sleep inertia duration than patients with OSA.

CONCLUSION

The French SIQ is a valid and reliable tool for assessing sleep inertia in sleep medicine populations.