Reliability and Validity of the Pittsburgh Sleep Quality Index-Serbian Translation

The aim of this study was translating and exploring psychometric properties of Serbian Pittsburgh Sleep Quality Index (PSQI) in a sample of "good" and "bad" sleepers suffering from depression or obstructive sleep apnea (OSA). Formal translation and validation were performed on a sample of healthy controls, patients with untreated OSA, and with diagnosed major depressive disorder with evaluation of internal consistency, test-retest reliability, and construct and criterion validity. Controls and OSA subgroups were recruited from a larger sample of commercial drivers. One hundred and forty subjects, 84.3% male, 22-67 years old, were included. OSA subgroup had 59 subjects and depression subgroup had 40 subjects (22 females). Mean ± SD total PSQI was 3.5 ± 2.2 in controls, 4.9 ± 3.6 in OSA subjects, and 9.0 ± 4.9 in patients with depression. Cronbach's α for total PSQI was 0.791. Subscale scores were significantly correlated to global PSQI in all subgroups. Intraclass correlation coefficient for global PSQI was 0.997 ( p < .001). Epworth Sleepiness Scale score was significantly correlated to global PSQI (ρ = 0.333, p < .001). Three subgroups differed significantly in total PSQI and PSQI ≥ 5, even after adjustments for age and gender ( p < .001). OSA patients had higher mean PSQI than controls but not significantly ( p = .272). PSQI-reported sleep latency did not correlate with PSG-measured sleep latency ( r = .130, p = .204). Total PSQI was significantly correlated to OSA severity (ρ = 0.261, p < .05). Serbian PSQI showed good internal consistency, test-retest reproducibility, and adequate construct and criterion validity, which supports further exploration of its use as a sleep quality screening tool in different target populations.